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ALBERT R.. MANN
LIBRARY

NEW YorK STATE COLLEGES
OF
AGRICULTURE AND HOME ECONOMICS

 

AT

CORNELL UNIVERSITY

 

 

 

 
ornell University Libra!

TAT
THE KILLING OF PLANT TISSUE
BY LOW TEMPERATURE

BY

WILLIAM HENRY CHANDLER, B. S. Acr., M. S. Acr.

SUBMITTED IN PARTIAL FULFILLMENT OF THE
REQUIREMENTS FOR THE DEGREE OF
Doctor oF PHILOSOPHY
IN THE

GRADUATE SCHOOL

OF THE

UNIVERSITY OF MISSOURI

1914
BIOGRAPHY

—__—

WittiAmM Henry CHANDLER

I was born July 31, 1878, on a farm in Bates county, Missouri.
My common school education was secured in the Public Schools of
this county, and, later, I attended the Butler Academy at Butler, Mis-
souri, For several years I served as a teacher in the public schools
of Butler county.

In September, 1901, I entered the College of Agriculture of the
University of Missouri. The degree of Bachelor of Science in Agri-
culture was given to me in 1905. For the school year of 1905-6 I
served as Fellow in Horticulture at the University of Missouri and in
June, 1906, took the degree of Master of Science in Agriculture. The
subject of my thesis was: “Winter Killing of Peach Buds as Influ-
enced by Previous Treatment of the Trees.”

In 1906, I became Assistant in Horticulture, University of Mis-
souri, and in 1909, Instructor in Horticulture. My rank was raised
to Assistant Professor of Horticulture in 1911. I was elected Pro-
fessor of Research in Pomology, Cornell University, in 1913, which
position I still hold.

I have published, or have in press, the following papers of the
Missouri Agricultural Experiment Station: |
Bulletin 74 The Winter Killing of Peach Buds as Influenced by

Previous Treatment of the Trees.
Bulletin 97 Co-operation Among Fruit Growers.
Bulletin 102 Combating Orchard and Garden Enemies.
Bulletin 113 Commercial Fertilizers for Strawberries.
Research Bulletin 8 The Killing of Plant Tissue by Low Temper-
ature,
Research Bulletin 14 Sap Studies with Horticultural Plants.
CONTENTS

PAGE
SOUT AT Y sersiviteva acwsn ve circ aaa dae Wie each ie nea seh ta dei g et ehacabere oe 143:
Review of Literature on Freezing ...........e.eceeeecueeees 149
Effect of Sap Density on Temperature .......... inter donh SSeae gasses 155
Experiments on Seedlings of Zea Mays .........eceeeeeeueees 158
Kjeldahl-Gumming Method for Estimation of Nitrogen ........ 184

Other Features that Influence the Freezing to Death of Plants,. 187
Effect of Previous Exposure to Temperature Slightly Above, Kill-

ing Temperature .j........ 0.0 ce gece eee eens Eas 223
Relation of Low Temperature to Peach Growing ............. 256
Varieties with the longest Rest Periods ...............0005. 269
Effect of Vigor of Trees on Rest Periods ................0005 272
Breeding Varieties Hardy under Missouri Conditions ......... 288
Killing of Apples) w:ctcineevecepemveve vas envewk na cadeee anes 293
Killing of Cherries Bi BI aI saceeic cecal ceed sheath 302
Acckniawledgrmnents: csisécssis ciissey sseiaie: aye ayaiove. sible oi tosece salto, aia: ca le aha or ons’ 303
Bibliography ........... Sion 2s vesrastonsiia edeasch anaun auatecepbataune ani aetebeg 305
THE KILLING OF PLANT TISSUE BY LOW TEMPERATURE.

W. H. CHANDLER.
Summary.

1. The term sap density, as often used in this publication, refers,
not to specific gravity, but to molar concentration. These sap den-
sities have been determined by the freezing point method, making
use of the fact that the molecular weight in grams of any non-elec-
trolyte lowers the freezing point 1.86° C. The sap density is gen-
erally given in terms of depression, meaning the number of degrees
Centigrade that the freezing point is lower than the freezing point
of water. :

2. By the eutectic point is meant the temperature at which
the substance in solution crystallizes out. At that temperature
there would be at the same time ice, crystals of the solute, and un-
frozen solutions.

3. There are several forms of injury from cold, some of them
purely mechanical, such as tearing of tissue due to tension developed
at low temperature, or evaporation from the surface when the con-
ducting tissue is frozen so as to prevent the movement of water to
that tissue, and killing as a result of long continued exposure to low
temperature. The term freezing to death, however, is applied here
only to a very specific set of phenomena. With all plant tissues,
when a certain temperature is reached very shortly after thawing,
it will be found that the tissue has taken on a brown, water-soaked
appearance, and evaporation from that tissue is much more rapid
than from living tissue. These are characteristics of plant tissue
frozen to death.

4. Results of many investigations have shown that during
freezing (which may or may not result in freezing to death), ice forms
in the tissue, generally not in the-cells but in the intercellular spaces,
the water moving out of the cells to form crystals in these spaces.
The most commonly accepted theory is that killing from cold results
from the withdrawal of water from the protoplasm. The amount
of water loss necessary to result in death varies with the different
plants and different tissues. (Pages 147-155).

5
; 6

5. In the experiments described in this bulletin, the killing
temperature of plant tissue that kills at relatively high temperature
has been reduced whenever the sap density of the tissue has been
increased. (Pages 155-187).

6. In addition to ripe apples and pears, and the leaves of Agave
Americana observed by Miiller-Thurgau and Molisch, leaves of let-
tuce kill at a slightly lower temperature if they are thawed slowly
than if thawed rapidly. In case of all other tissues tested by this
station or by others, including unripe apples and pears, there is no
indication that the rate of thawing has anything to do with the
amount of killing at a given temperature. (Pages 187-194).

7. Rapid wilting of tissue has not generally increased the re-
sistance of plants to low temperature over that of unwilted tissue
with a dry surface. However, tissue with a wet surface killed worse
at a given temperature than did tissue with no moisture on the sur-
face. (Pages 194-198).

' 8. Slow wilting or partial withholding of water through a long
period increased the resistance of tissue to low temperature. (Pages
198-199),

9. In case of hardy winter buds and wood, a rapid decline in
temperature greatly increased the severity of injury from a given low
temperature. (Pages 199-218).

10. There seems to be no constant relation between the rate
of growth of plant tissue and resistance to low temperature. Young
leaves of fruit trees kill at a higher temperature than doold, mature
leaves, while the young leaves of lettuce withstand a lower tempera-
ture than do the older leaves. (Pages 218-222).

11. Previous exposure to low temperature above that at which
the tissue kills seems to increase the resistance of tissue to low tem-
perature. (Pages 223-224).

12.’ The most important feature affecting the hardiness _of
plant tissue is maturity, that is, the condition of resistance that
the plants reach during the winter dormant period. Maturity in the
case of cambium may be intimately associated with the process of
drying out. However, this can not be true at least of cortex of win-
ter twigs. There is little difference between the moisture content
of unfrozen cortex in seasons when it is very tender and seasons
when it is hardy. The wood at the base of the trunk and at the
crotches of all rapidly growing branches seems to reach a condition

of maturity in early winter more slowly than does most other tissue.
(Page 224).
7

13. Of the tissue above ground during periods when the most
complete maturity is reached, the most tender parts are the pith
cells and the fruit buds. During periods of rapid growth there is
little difference in hardiness of the different tissues. The tissue
which is most tender at all seasons of the year is the root. There
is much less difference, however, in the killing temperature of roots
in summer and winter than between the killing temperature of twigs
or other wood in summer and winter. (Pages 224-239).

14. Roots of the French crab used as stock seem to be more
tender than roots which come from scions of an average variety of
apple. (Pages 239-243).

15. Marianna plum roots are certainly more hardy than Myro-
bolan roots, and Mahaleb cherry roots seem slightly more hardy than
Mazzard roots. (Pages 243-252).

16. That part of the root system nearest the surface and the
largest, oldest roots are more resistant to cold than are small roots
further from the surface. (Pages 233-252).

17. Pollen of the apple will withstand much lower temperatures
than will any other tissue of the flower when in full bloom. (Page
253). ;

18. Scales of peach buds do not serve to protect them from low
temperature. Buds frozen in the laboratory with the scales removed
were slightly more resistant to low temperature than were buds with
the scales not removed. (Pages 254-256).

19. The killing of wood of peach trees from freezing is one of
the most important determining factors in peach growing. Little
can be done to influence the amount of killing except to have the trees
start into winter in proper condition of maturity. The weakest
growing trees, however, do not generally reach this condition of ma-
turity in the most satisfactory manner. Trees one or two years in
the orchard, or old weak trees, are most liable to succumb to effects
of low temperature. Pruning the trees severely following a winter
when the wood has been killed, altho apparently in the best condition
of maturity, seems to reduce the amount of killing. However, such
pruning following winters when the wood has been killed on account
of its not having reached the proper condition of maturity in the fall,
generally due to the presence of wet weather following a drought the
season before, is liable to result in greater loss than if no pruning
were done. (Pages 256-266).

20. The hardiness of peach buds when in fully dormant condi-
tion seems to be ‘greatly increased by continuous low temperature
preceding the date at which the temperature goes low enough to kill.
This capacity to withstand low temperatures seems likely to be due
8

to the slow fall in temperature under such conditions rather than to
hardiness developed as the result of exposure to low temperature.
(Pages 266-269).

21. Inthe peach growing district of South Missouri and Arkan-
sas, and probably other similar climates, the most important factor
influencing the loss of peaches from low temperatures in winter is
keeping the buds from starting into growth during warm periods in
winter. In that section the best means of accomplishing this end
is prolonging the growth of the trees in autumn, either by heavy
pruning or by fertilizing with nitrogen the spring before. Some
varieties of peaches have a much longer rest period than other varie-
ties and therefore are started into growth more slowly by warm pert:
ods in winter. (Pages 269-283).

22. The killing temperature of peach blossoms when the tree
is just coming into full bloom, under Missouri conditions, seems to
vary from about 22° F. to 25 or 26° F. After the blossoms are old
enough that they are probably pollinated, and from that time on
until the peaches are as large as one-half inch in diameter, at least,
they continue to become more tender until they will withstand but
very few degrees below the freezing point, the seeds of young peaches
killing at a higher temperature than other peach tissue. Pages 283-
286).

23. So far the investigations at this station indicate ae early
varieties of peaches are not started into growth more readily by warm
periods in winter than are later varieties. Some of the very early
varieties of the Chinese Cling group are the most slowly started into
growth in early winter and bloom as late as any of the varieties. How-
ever, after blooming time these early peaches grow much more rap-
idly and are much more liable to be killed by a freeze after the fruit
is set. (Pages 286-293). \

24. Killing of wood of the apple is of considerable importance
in some apple growing sections. Among the most common injuries
are root killing, crown rot, crotch injury, sun scald, trunk killing
and killing back of top and branches. (Pages 293-297).

25. Killing of apple buds from low temperatures is not common
but has been observed. (Pages 297-298). .

26. The blossoms and young fruit of the apple will not generally
withstand as low temperature as will the blossoms or young: fruit of
equal age of the peach. (Pages 298-302).

27. While the killing of cherry and plum buds is oe common
than the killing of buds of the peach, such killing is often to be ob-
served in some sections. The young fruit of the Wild Goose plum
is among the most resistant to late frostsin spring. (Pages 302-303).

i
1
1
2

STUDIES ON THE KILLING OF TISSUES OF HORTICULTURAL
PLANTS BY LOW TEMPERATURE

The work to be reported in this paper was begun during the
season of 1904-05. At that time the studies concerned only the
effect of certain cultural methods on the hardiness of the fruit buds
of the peach under climatic conditions that prevail in the southern
half of Missouri. Later they were extended to include the possible
effect that a large amount of potassium or other mineral elements
in the soil might have on the ability of the peach fruit buds to with-
stand cold.

In taking up this problem it is necessary to distinguish between
some of the various phases of injury from cold. Various writers
have mentioned observations on frost cracks, that is, a formation
of cracks in the wood of the tree during freezing weather. Caspary?
showed that the formation of these cracks is due to a greater contrac-
tion of the tissue of the tree tangentially than radially. Later,
Miiller-Thurgau? made a very careful study of these cracks and
confirmed Caspary’s opinion, but showed that this great contraction
tangentially is due rather largely to the shrinking of the cells of the
medullary rays. These medullary rays extend in lines from the
center out, and are made up of rather thin walled cells separated no-
where by very rigid tissue. These rays separate wider strips of
rigid tissue extending in a wedge shape from the surface to the center
with no lines of more pliable tissue crossing them. Then where the
cells of the medullary rays contract on the passage of water into the
intercellular spaces to form ice crystals, shrinking toward the center
is limited to the rate of shrinking of the strong wedges of rigid tissue,
while radially there is the shrinking of the rigid tissue and the more
rapid shrinking of the medullary ray tissue.

There seems to be another type of injury® to the wood of trees,
especially the small twigs, due apparently to the fact that during
a long cold period much moisture will be lost from these twigs that
can not be replaced because of the frozen condition of the conducting
tissue. Thus death will result from the great loss of water from the
twigs by evaporation. Killing of this kind seems to be worse in
regions with prevailing strong winds and continuous low winter tem-
perature. Thus Allen‘ finds a rather direct correlation between the

‘Bot. Zeit. Vol. 13, pp. 449-62, 473-82, 489-500 (Bibl. No. 17); Bot. Zeit. Vol. 15, pp
329-35, 343-50, 361-71 (Bibl. No. 19).

2Landw. Jahrb. Vol. 15, p. 453, 1886 (Bibl. No. 78).

3A. Nelson, Wyo. Agr. Exp. Sta. Bul. 15, 1893. (Bibl. No. 81).

4Master’s Thesis, Iowa Agr. Exp. Sta. (Bibl. No. 2).
10

hardiness of the different varieties of apples and the rate at which
water will be evaporated from their twigs.

Another form of injury, at least an injury that has been attribut-
ed to the effect of low temperature, results in the formation of dead
areas on the bark of the tree trunk, especially near the top of the
ground or in the crotches formed by the branches. Such injury has
been studied by Goeppert!, Sorauer’, Grossenbacher® and others.
Grossenbacher finds this injury greater on the side of the tree next
to the prevailing wind, indicating that the great evaporation from
the bark during a long period when it is frozen, and especially the
tearing due to the bending of the tree when the bark is under high
tension, may have something to do with this form of injury. This
may not be a different form of injury from direct freezing to death
which will be discussed later.

Sachs observed that the foliage of certain plants wilted following
exposure to a temperature above the freezing point. He and also
Miiller-Thurgau‘ conclude that this wilting was not due directly
to the effect of cold, but indirectly to the inability of the roots to
take up moisture at so low a temperature to replace the evaporation
from theleaves. According to Molisch®, plants continuously exposed
to a temperature too low for normal metabolism, but above the
freezing point, will eventually die. Under these conditions, death
ensues more slowly than where plants are killed by a sudden freeze.
The plants gradually turn yellow and die, or dark colored dead
spots are formed on the foliage.

Miiller-Thurgau® limits the term freezing to death (‘‘erfrieren’’)
to the most common phenomena to which we have reference in speak-
ing of killing from cold. It is death of the tissue following, directly,
the lowering of the temperature below the freezing point, with the

ccompanying formation of ice crystals. When plant tissue is thus
rozen to death in the case of growing plants, the foliage in prac-
tically all cases has a wilted or limp appearance. Pronounced color
changes take place. Thus in most cases the green color due to the
chlorophyll is lost, and the tissue takes on a brownish watery color.
Plant cells containing coloring matter give up this coloring matter
to the adjoining cells of the liquid in the intercellular spaces. Other

‘Ueber die Warmeentwickelung in dem Pflanzen, etc. Book, 1830. (Bibl. No. 44).
2Landw. Jahrb. Vol. 35, pp. 465-525. 1906. (Bibl. No. 105).

IN. Y. Geneva, Agr. Exp. Sta. Tech. Bul. 23, (Bibl. No. 50); N. Y. Geneva, Agr. Exp.
Sta. Tech. Bul. 12, (Bibl. No. 51).

4‘Landw. Jahrb. Vol. 15, p. 453, 1886. (Bibl. No. 78).

‘Untersuchung tiber das Erfrieren, etc. 1897, Book. (Bibl. No. 75).

SLandw. Jahrb. Vol. 15, p. 453, 1886. (Bibl. No. 78).
il

color changes often take place, due to chemical changes when the
coloring matter comes in contact with other substances from other
cells. Death! can often be detected by these color changes. In the
case of certain buds, and especially the stem and root tissue of hardy
trees, the changes indicating this sort of death from cold can not
be detected so soon after thawing, but are very characteristic, the
tissue showing the watery, brownish appearance in a few hours after
thawing. In all cases water is very rapidly lost from tissue killed
in this way. Thus Goeppert? has shown that 24.25 grams of frozen
canna leaves, which on thawing proved to be dead, lost when kept
for six days in the open air near a warm stove, 21.25 grams, while
the same weight of live canna leaves lost in the same length of time
only 11.27 grams. When the killing temperature is barely reached,
not all of the tissue is likely to be killed, but often there will be spots
of dead tissue with live tissue adjoining. It has been observed by
Sorauer and others, that the number of dead cells does not increase
beyond those that are easily observed to be dead a short time after
thawing. However, it requires longer for death to be plainly ob-
served in the case of some tissues than others. As mentioned above,
the tissue of the sap wood and cortex does not show plainly whether
or not it is dead as soon as does the tissue of leaves and buds. Sorauer®
found that epidermal tissue is slower in showing death after thawing
than other tissues.

REVIEW OF THE LITERATURE ON FREEZING TO DEATH

In this paper the term freezing to death will be used as it was
used by Miiller-Thurgau, only when referring to the phenomena
just described. While some early observers were of the opinion that
plants have the ability to generate heat within their tissue and thus
avoid severe freezing, the early Greek philosophers, observing the
presence of ice within the plant tissue and not knowing of the cellu-
lar structure, were of the opinion that the injury was due to rending
and mashing organs by the ice formation. Du Hamel and Buffon‘
were among the first to present a theory of the cause of death from
cold based on a partial knowledge of cellular structure. They be-
lieved killing to be a rupturing of the cell walls due to the expansion
accompanying ice formation,

1Molisch, Untersuchung tiber das, etc. 1897. Book. (Bibl. No. 75); Muller-Thurgau,
Landw. Jahrb. Vol. 15, p. 453, 1886. (Bibl. No. 78).

2Ueber die Warmeentwickelung, etc. Book, 1830. (Bibl. No. 44).

3Landw. Jahbrb., Vol. 35, pp. 469-525, 1906. (Bibl. No. 105).

4Mem. d. ]’Acad. Roy. Sci., Paris, 1737, pp. 273-298. (Bibl. No. 30).
12

Goeppert! was among the first to make a careful study of killing
from cold. He observed the formation of ice within the cells, and
also in the intercellular spaces. Sachs? found thatit was almost always
in the latter.

Miiller-Thurgau® in his very excellent studies found that when
the ice crystals were found within the cells, it was due to very rapid
freezing such as Goeppert used, and when the temperature was low-
ered very slowly, ice crystals were seldom found within the cell.
Miiller-Thurgau proved that ice formation within the tissue is neces-
sary to freezing to death. It is well known that a liquid may often
be supercooled several degrees below the freezing point before ice
formation begins. He observed that this often occurs in cooling
plant tissue in the laboratory, and when pieces of tissue (potato)
were supercooled, if they could be warmed without ice formation
they were not injured, while if ice formed they would kill at a higher
temperature than that to which they were supercooled. Voigt-
lander measuring his temperatures with more delicate apparatus,
has proved this perhaps more conclusively. When he supercooled
tissue to four or five degrees centigrade below the point at which it
would kill when ice formed, if the temperature could be raised to
above the freezing point without ice formation, killing never occurred.
It was held by many scientists, at the time of Miiller-Thurgau’s
first work, as well as by a large majority of practical observers, that
death was due not directly to low temperature, but to rapid thawing.
Goeppert was of the opinion, however, from his studies, that the
killing was a direct result of freezing and that death actually occurred
before the thawing began. Sachs, from some experiments with
plants immersed in cold water to thaw, after freezing, held that
the amount of killing of the plants at any given temperature was
determined by the rate of thawing. Miiller-Thurgau showed that
the method used by Sachs of thawing plants in cold water was not
a method of slow thawing, but rather a very rapid thawing since a
layer of ice crystals would form on the outside of the tissue, giving
off heat that would thaw the tissue very rapidly. In fact the tissue
thawed in cold water much more rapidly than in the air at room
temperature.

Miiller-Thurgau using a large number of plants, thawing them
from the same temperature, some rapidly and some more slowly,

‘Ueber die Wirmeentwickelung, etc. Book. 1830. (Bibl. No. 44).

*Ber. u. d. Ver. d. Kon. Sachs. Gesell. d. Wiss. zu Leipzig, 1860, Vol. 12, pp. 1-50. (Bibl.
No. 94).

‘Landw. Jahrb. Vol. 15, p. 453, 1886. (Bibl. No. 78).
¥3

was never able to detect any difference in the amount of killing when
thawed rapidly or slowly, except in the case of the fruit of the apple
and pear. Molisch!, following the work of Miiller-Thurgau, tried
also slow and rapid thawing from the same temperature with a very
large number of plants, and found that in nearly all cases the rate of
thawing had nothing to do with the killing. In the case of the fruit
of the apple and pear, and the leaves of Agave Americana, the slow
thawing gave less injury, but even with these, a slightly lower tem-
perature than that at which they kill with rapid thawing, would kill
them, regardless of the rate of thawing. Miiller-Thurgau observed
carefully the freezing of tissue under the microscope and found that
ice was very seldom formed within the cell, but usually ice crystals
formed outside the cell in the intercellular spaces and continued to
increase in length as the temperature went lower, the water passing
from the cell into the intercellular spaces increasing the length of
the crystals.

By placing plant tissue frozen to various temperatures in 100
cc. of water carefully insulated, and noting the temperatures to which
the water was lowered, excluding the losses of heat for warming up
the plant tissue, correcting for the heat of the beaker, etc., making
use of the fact that eighty gram calories are required to melt one
gram of ice, Miiller-Thurgau? was able to determine, apparently
with some accuracy, the percentage of the plant water that is frozen
into ice at various temperatures. Only plant tissue with a deter-
mined moisture content was used. With the apple he gives the fol-
lowing percentages of water frozen out at given temperatures: at
-4.5°, 63.8 per cent of the water was frozen; at -13°, 74.4 per cent of
the water was frozen; at -15.2°, 79.2 per cent of the water was frozen
He also attempted to measure the percentage of the water frozen out
of woody tissue by means of frost cracks. His method was to freeze
a section of a young tree trunk until a frost crack of a certain width
was formed. On thawing of the tissue this crack would close. His
next step was to dry the section of tree trunk until a frost crack of
the same width was formed. He assumed that the percentage of
water loss necessary to form this crack is equal to the percentage
taken from the cell during freezing sufficient to form an ice crack of
the same width.

Molisch studied with great care, under the microscope, the
freezing of various plant tissues, observing the same phenomena de-

tUntersuchung tiber das, etc. 1897, book. (Bibl. No. 7°).
*?Landw. Jahrb. Vol. 9, p. 453, 1886. (Bibl. No. 78).
14

scribed by Miiler-Thurgau with reference to the freezing of the cell
water in the intercellular spaces, rather than within the cells. Both
Miiller-Thurgau and Molisch hold the view that freezing to death
results from the rapid withdrawal of water from the cells to form
these ice crystals in the intercellular spaces.

Matruchot and Molliard! observed that water is extruded from
the nuclei of plants that have been frozen, dried or subjected to the
action of solutions of high osmotic concentration.

Gorke has recently offered an interesting theory as to the cause
of death by freezing. He found that when the plant sap is frozen,
certain proteids may be precipitated out and apparently those plants
that are most easily killed by freezing have their proteids precipitated
out at the highest temperature. Thus begonia, which is very easily
killed, had its proteids precipitated at -3° while sap from pine needles
required a temperature of -40° to precipitate any proteids. Gorke’
assumes then that killing from cold may be due to the precipitation
of the proteids, and accounts for this precipitation by the greater
concentration of the salts in the sap as water is removed to form ice
crystals. It is well known that certain proteids can be precipitated
out by increasing the concentration of salts, especially zinc sulphate
and ammonium sulphate. Gorke made up solutions of albumen
with zinc sulphate and found that after freezing to -20° there was a
large precipitation of proteids.

Lidforss® working with the wintergreen plants of South Swed-
en, has found that-with most of them at least during cold weather,
the starch is almost entirely changed to sugar, though on the return
of warm weather starch may be again deposited in the cell. He
assumes that this sugar is formed during cold weather as a means
of protecting the plant against freezing by lowering the freezing
point of its sap. He was able also to increase the resistance to low
temperature of the leaves of wintergreen plants and the roots of
Zea Mays by keeping therp-for a time immersed in 5 to 10 per cent
sugar solutions.

Schaffnit*, following the work of Gorke, found that the pro-
teids of rye grown in the open at low temperatures are not readily
precipitated by freezing, while the same temperature will readily |
precipitate proteids from sap of rye grown in the greenhouse at much’

1Compt. Rend. Acad. Sci. Paris, Vol. 132 (1901) pp. 495-8. (Bibl. No. 71a)

*Land. Versuchs. Vol. 65, p. 149, 1906. (Bibl. No. 47).

3Lunds Universitets Arssk., Vol. 2, No. 13, 1907 (Bibl. No. 62); Bot. Centlb., Vol. 68
No. 2, p. 33. (Bibl. No. 63).

‘Mitt. Kaiser Wilhelm Inst. Landw. Bromberg, Vol. 3, No. 2, pp. 93-115, (Bib). No.
98); Zeits. f. Allg. Phys., Vol. 12, pp. 323-36. (Bibl. No. 99)
15

higher temperatures. He also found that he could prevent the pre-
cipitation of proteids from this sap of greenhouse rye by adding to it
small quantities of sugar. He concludes then that the formation
of sugar in wintergreen plants described by Lidforss may be the
means of protecting the plants against precipitation of proteids.
However, Schaffnit concludes that precipitation of proteids is the
only way by which loss of water during freezing kills plant tissue.

Maximow! has recently published three very interesting papers
covering work in freezing sections of plants, mainly red cabbage and
Tradescantia discolor. Thin sections of tissue from the upper side of
the leaves were frozen in solutions of various strengths of both organic
and inorganic substances after they had stood for varying lengths
of time in the solutions. He found remarkable protection to be ex-
erted by both organic and inorganic substances whenever their
eutectic point (the temperature at which they crystallize out, giving
mixtures of solute crystals with the ice crystals) does not lie too
near the freezing point and whenever the substance is not excessively
toxic. He used strengths varying from 5 to 2N of glucose and
glycerine, and a to 2N of methyl and ethyl alcohol, and mannite.
Of inorganic substances he used solutions with strengths of 0.1N
to 2N of sodium chloride, potassium chloride, calcium chloride,
sodium nitrate, potassium nitrate, calcium nitrate, sodium acetate,
potassium acetate, calcium acetate, sodium lactate, potassium lac-
tate, sodium oxalate, and potassium oxalate, also magnesium nitrate,
magnesium chloride, ammonium nitrate, ammonium chloride, sodium
sulphate, and potassium sulphate.

According to Maximow, mannite, sodium sulphate, potassium
sulphate. potassium nitrate, and sodium oxalate show little protec-
tion because of their high eutectic point; and magnesium chloride,
magnesium nitrate, and ammonium chloride because of their toxicity,
while calcium chloride and calcium nitrate show reduced protection
because of their toxicity. ‘All other solutions, however, showed
great protection that was very uniform for the same osmotic con-
centration. Sometimes a temperature as low as -32° did not kill all
of the cells of the red cabbage. Probably the most interesting re-
sult of Maximow’s work was the observation that when the sections
were immersed in these solutions and immediately frozen, as much
protection was exerted as when they had been permitted to remain
in the solutions for twenty-four hours or longer. The tender Trad-
escantia cells immersed in expressed sap of the red cabbage and im-

'Ber. der Deutsch. Bot. Gesell.. Vol. 30, pp. 52-65, 293-305, 504-16, (Bibl. No. 73°
16

mediately frozen, would actually withstand more cold than the
hardier red cabbage when frozen in winter. Maximow concludes
that the part of the cell which is injured when exposed to low temper-
ature is the plasma membrane, and that as long as a film of water
was kept in contact with this membrane, death was not likely to occur
His theory then would not be greatly different from that of Miiller-
Thurgau and Molisch, that withdrawal of water kills, except that in
Maximow’s opinion killing following the withdrawal of water seems
to be limited to the plasma membrane.

If Maximow’s work is verified by further experimenting, using
other plants, it is certainly a very interesting contribution toward
determining just what freezing to death of plant tissue is.

Mez! studied the effect of supercooling upon plant tissue. He
finds that where ice formation begins at once on reaching the freezing
point, the killing is not so great as where there is supercooling when
large masses of ice are formed rapidly after crystallization begins.
By use of the thermo-couple he studied the fall of temperature in the
plant, using stems of Impatiens to determine the eutectic points
of the sap solutes. At each of these points there will be a halting
in the temperature fall due to the heat given off on crystallization.
From this work he concludes that when a temperature of -6° is
reached, all solutes will crystallize out. He thinks this should dis-
prove the theory of Miiller-Thurgau and Molisch, since there should
be complete loss of water at this temperature and the plant should
never survive a lower temperature if loss of water from the cell is the
cause of death. He holds that the heat liberated by the crystallizing
of the solutes and the formation of i ice, willafter the cells are insulated
by the icé mass, aid in keeping the temperature of the cell above
that of the surroundings. He holds, therefore, that each plant has
its specific minimum point at which death occurs due to the direct
effect of the cold, and that if supercooling takes place, large amounts
of heat are lost before the cells are insulated by the ice mass and
therefore this specific minimum will be more quickly reached. The
work of Miiller-Thurgau” and of Voigtlander’, (a pupil of Mez)
where plants supercooled to below the killing temperature remained
alive if ice did not form, certainly refutes the theory of Mez. If
further evidence were needed, the protective action of organic and
inorganic substances shown in Maximow’s work certainly proves the
fallacy of Mez’s conclusion. Even his conclusion that the sap solute

Flora, Vol. 94, p. 89, 1905. (Bibl. No 74).
*Landw. Jahrb. Vol. 15, p. 453, 1886. (Bibl. No. 78).
5Beitr. z. Biol. der Pfl. Cohn. Vol. 9, 1909. pp. 359-414. (Bibl. No. 110).
 

 

 

 

FIGURE I.—FREEZING APPARATUS FOR PLANTS’ THAT
KILLED AT A TEMPERATURE NOT LOWER THAN —12° TO -15° C.

1. Space in which salt and ice mixture was placed;

2. Chamber in which plants were frozen;

3. Lid which covered freezing chamber;

4. Wire leading to small electric fan beneath hardware cloth
bottom on which plants were frozen. (See page 156.)
 

 

 

 

 

 

FIGURE Il.—APPARATUS FOR FREEZING TISSUE THAT RE-
QUIRED LOWER THAN —12° TO —15° GC. TO KILL.

1. Galvanized iron cylinder to the bottom of which the twigs con-
taining buds were fastened; 2 and 3. Galvanized iron cylinders placed
One within the other with space between their walls for freezing mixture;
4. Cylinder to receive 3, allowing space for freezing mixture around 3;
5. Insulating box filled with sawdust; 6. Wheel operated by electric
motor and belt in order to keep (1) turning continuously while freezing;
7. Lid for (2). (See page 157.)
 

 

 

FIGURE IIl.—APPARATUS FOR EXPRESSING PLANT JUICE.

The two blocks between which the plant tissues were pressed are
shown at (1) and (2). The juice escaped through a hole (3) in block
(1). The plant tissue was placed between the blocks (1) and (2),
which in turn were placed between the pieces of movable 4/’x4/” pieces
which are drawn together by bench-screws. (See page 158.)
 
17

must all be crystallized out at -6° C. can not be true since sugars
would remain in solution at lower temperatures than that. Further,
when we have evaporated the cortex sap of peach twigs in winter
condition to one-sixth or one-eighth of its volume without permitting
the temperature to go above 50° C. ice would not form when the
temperature was lowered to -22° C. though many of the buds would
be killed at that temperature. Mez seems also to ignore the force
of imbibition which would tend to hold the water in the protoplasm
even after the sap solute may be crystallized out. The fact, however,
that when great supercooling takes place, plants are more liable to be
killed, is of interest and is, of course, associated with the fact which
will be discussed later that rapid cooling is more injurious to plant
tissue than is slow cooling.

EFFECT OF SAP DENSITY ON KILLING TEMPERATURE.

If the theory of Miiller-Thurgau and Molisch be true (even as it
is modified by Maximow) it would seem that some plants might
be hardy because the plasma membrane has the property of with-
standing great loss of water. Some might be relatively hardy be-
cause of a property by which sufficient water to protect the plasma
membrane at low temperatures is prevented from freezing, and some
might be relatively hardy on account of the presence of both condi-
tions. Itis generally considered that after the effect of the sap solute
in holding water unfrozen is exhausted, there is still left the force of
imbibition. The relative importance of these two forces, however,
is not determined. Disregarding the force of imbibition (which,
however, may be the more important), it would appear to be true that
if the sap density (by sap density is meant not specific gravity but
molar concentration of the sap; that is, the number of gram molecules
of the sap solute in one thousand grams of water) were doubled, then
at any given temperature below the freezing point, but above the
eutectic point of the solute, twice as much water would be held un-
frozen to protect the protoplasm.

With this idea in mind, experiments were started in September,
1908, to determine whether or not an increase in the sap density
would lower the killing temperature.

Seedlings of corn, cowpeas, garden peas, tomatoes, squash,
cabbage and lettuce were grown in sand and watered with varying
strengths of potassium chloride and ammonium chloride at first—
later magnesium chloride, sodium chloride and sodium nitrate were

also used—while check plants were grown under similar conditions
2
18

except that they were watered only with distilled water. The plants
were permitted to grow only as long as they would make good growth
in the sand, probably about the time the food supply of the seed was
becoming exhausted. Some of the plants of each set were then frozen
while others had the sap expressed for osmotic strength (freezing
point) determination by the use of a Beckmann apparatus. As a
measure of the osmotic strength the term depression will be used in
the tables, meaning of course the number of degrees centigrade be-
low zero at which, with no supercooling, ice formation begins in the
sap.

Method of Freezing. At first an effort was made to grow the
plants in the greenhouse and expose them to outside temperatures
to determine the killing temperature. However, this was soon found
to be unsatisfactory and the plants were frozen in a chamber sur-
rounded by a freezing mixture made of salt and ice. It is evident
that the temperature throughout such a chamber would not be uni-
form so long as it were falling and great care was necessary to secure
as uniform a temperature as possible. The apparatus shown in
Fig. 1 was used. In the lower part was an electric fan; the upper
part was the chamber in which the plants were frozen. An effort was
made to keep the temperature uniform within this chamber by the
operation of the electric fan just beneath the hardware cloth shelf
on which the plants were frozen. Careful tests showed that the
temperature throughout this chamber was always uniform on the
same level though sometimes it would vary slightly in different levels.
Fearing, however, that this would not always be true, the plants on
freezing were always placed, not only on the same level, but at the.
same distance from the galvanized iron wall of the chamber. In
this way it was practically impossible that plants in the freezer would
not all be exposed to the same temperature, and consistent results
were secured.

In addition to being sure that the plants were at a uniform tem-
perature, it was necessary to control very carefully the rate of fall
of the temperature, since rapid falling of temperature very greatly
increases the killing. For this reason it was practically impossible
to secure results that would be sufficiently accurate so that one freez-
ing could be compared with another, except where differences were
wide; that is, the plants to be compared must be frozen at the same
time. However, when the differences are large it is possible to make
a fairly accurate estimate of the relative hardiness of the plants
frozen at different times, if great care is taken to duplicate as nearly
as possible, the rates of temperature fall. It was found possible to
19

lower the temperature of all the plants together to a point that would
probably kill the most tender, and after removing these to lower it
further. The rate of fall would thus be the same for all down to the
temperature at which the most tender were removed.

The thermometer used in the earlier years of freezing was a
pentane thermometer graduated to one-half degrees. The zero
point was far enough above the bulb so that when the thermometer
was inserted through a cork at the top of the jacket of the freezing
chamber, the bulb would be on the same level with the plants. Later,
special mercury thermometers graduated to low temperature were
used. These were standardized by the makers. However, new
thermometers were checked by those used with previous work, and
also, checked from time to time, with standard thermometers of the
Columbia Branch of the United States Weather Bureau. Noeffort was
made to read the thermometers to closer than one-half degrees. Plants
on being removed from the freezer were always examined to see if the
tissue were frozen stiff. In freezing buds and woody tissue that
killed at a temperature lower than -15°, the apparatus shown in
figure 2 was used. The twigs or pieces of tissue and the thermometer
were fastened to the inner cylinder which was filled with cotton.
This was set in a cylinder enough larger to leave a surrounding space
of about three-fourths of an inch. The second cylinder was about
six inches taller than the inner one, and was set with a one and one-
half inch space between them. There was about two inches of space
between the walls of this third cylinder and those of the one in which
this was placed. The fourth cylinder was well insulated by being
packed in dry saw dust. Ice and salt were first packed loosely and
then firmly in the space between the fourth and third cylinder. In
this way the temperature of the twigs could be lowered generally to
-17° C. When it was necessary to secure a lower temperature, the
space between the third and second cylinders was packed loosely and
later firmly with salt and ice. In this way the temperature of the
air surrounding the inner cylinder could be gradually lowered at the
rate of two to three degrees an hour after the freezing point was
reached. By packing salt and ice to the top of the second cylinder
the temperature from top to bottom of the inner cylinder would
vary but little. However, the freezing tissue to be compared and the
thermometer bulb were always kept the same distance from the bot-
tom of the cylinder. Since these cylinders were of galvanized iron
and would conduct heat rapidly, it would seem probable that the tem-
perature around the central cylinder would not vary. However,
fearing that there might be some such variation in temperature, the
20

central cylinder with the twigs or woody tissue and the thermometer
on its surface was kept slowly revolving by means of a small electric
motor. During the freezing, this was stopped only for thermometer
readings which were taken generally every fifteen minutes.

Method of Determining Freezing Point of Sap. The density
of sap was determined by means of a Beckmann Freezing Point Appa-
ratus. The tissue was ground in an ordinary food grinder, using the
knife that grinds the finest, and the sap was expressed with the appa-
ratus shown in Figure 3. The large block with the hole in the center
is of sugar maple which will not split readily. The smaller block
is of the same material and is made to fit in the depression in the large
block leaving about one-eighth of an inch surrounding space. The
ground tissue was wrapped in a clean piece of eight or ten ounce duck
and put in the depression in the large block, the small block put

- against it and the two pressed together between pieces of 4x4 lumber
drawn together by a pair of bench screws as shown in the figure.
The sap could be expressed very quickly. With succulent plants
loss by evaporation in all cases was negligible. In the case of leaves
of peaches it required a considerable length of time for the sap to
exude.

In all cases before plants with different treatments were frozen
or before they were ground for expressing sap, they were, after being
pulled, kept with the roots in a glass of water until they became
apparently turgid, since wilting sometimes seems to reduce slightly
the killing temperature, and would appreciably affect the sap density
determinations.

EXPERIMENTS WITH SEEDLINGS OF ZEA MAYS

A large number of corn seedlings were grown and frozen. The
following table gives the date of freezing, the solution with which
the material was watered, the temperature to which the plants were
subjected, the percentage killed and percentage partly killed, and the
freezing point of the sap. The freezing point is given as depression,
meaning the number of degrees below zero, centigrade, at which ice
begins to form in the sap, assuming no supercooling.
21

TABLE 1. SHOWING EFFECT OF WATERING WITH MINERAL SOLU-
TIONS ON SAP DENSITY AND HARDINESS IN ZEA Mays PLANTS.

 

 

Per-
Temper- | Num- | Percent-| centage
Watered Date ature ber age Killed | Depres-
With Plants | Killed and sion
Partly
Killed
Potassium Chloride
(.0804 N)........ Dec. 12,’08] -3 6 33.3 83.3 1.10
Potassium Chloride
(.0402 N).........|/Dec. 12,’08) -3 6 16.6 100 1.06
Ammonium Chloride
(.0804 N)......... Dec. 12,’08} —3 6 33.3 100 94
Ammonium Chloride rey
(.0402 N)......... Dec. 12,’08| -3 6 50 100 1.19
Potassium Chloride
(.0804 N)......... Dec. 15,’08} -3 6 33.3 33.3 1.265
Potassium Chloride .
(.0402 N)......... Dec. 15,’08} -3 5 40 60 .94
Ammonium Chloride 253
(.0804 N)......... Dec. 15,’08] -3 4 0 0 1.16
Ammonium Chloride
402 N)......... Dec. 15,’08) -3 6 100 100 875
Potassium Chloride
(.0804 N)......... Dec. 16,’08) -3.25 7 42.8 71.7 1.26
Potassium Chloride
(.0402 N)......... Dec. 16,’08) -3.25 7: 14.3 57.1 94
Ammonium Chloride beg
(.0804 N)......... Dec. 16,’08} -3.25 6 50 100 1.16
Ammonium Chloride
(.0402 N)......... Dec. 16,’08] —3.25 9 33.3 88.9 .875
Potassium Chloride
(.0804 N)......... Jan. 9,'09| -7 13 46.2 61.5 1.315
Potassium Chloride
(.0402 N)......... Jan. 9,'09} -7 11 63.6 81.8 1.195
Ammonium Chloride
(.0804 N)......... Jan. 9,’09| -7 9 77.8 100 1.005
Ammonium Chloride
(.0402 N)......... Jan. 9,'09| -7 12 66.6 100 -935
Potassium Chloride
(.0804 N)......... Jan. 9,’09] -6.5 11 27.3 54.5 1.315
Potassium Chloride
(.0402 N)......... Jan. 9,’09) -6.5 13 61.5 84.6 1.195
Ammonium Chloride
(.0804 N)......... Jan. 9,09! -6.5 10 80 90 1.005
Ammonium Chloride
(.0402 N)......... Jan. 9,’09) -6.5 14 50 85.7 .935
Potassium Chloride
(.0804 N)......... Jan. 9,’09) -7.5 13 61.5 76.9 1.315
Potassium Chloride
IN) isiscreese Jan. 9,’09) -7.5 12 75 83.3 1.195
Ammonium Chloride
(.0804 N)......... Jan. 9,'09) -7.5 8 87.5 100 1.005
Ammonium Chloride
(.0402 N)......... Jan. 9,’09) -7.5 12 91.6 91.6 .935
Potassium Chloride
(.0804 N)......... Jan. 19,’09) -3 12 16.6 50 1.315

 

 

 

 

 

 

 
22

 

 

 

 

 

 

Per-
Temper-| Num- |Percent-| centage
Watered Date ature ber age Killed | Depres-
With Plants} Killed and sion
Partly
Killed
Potassium Chloride
(.0402 N)....--++- Jan. 19,'09| -3 16 18.8 43.8 1.195
Ammonium Chloride :
(.0804 N).......-. Jan. 19,’09) -3 17 11.8 41.3 1.005
Ammonium Chloride
(.0402 N)........- Jan. 19,'09) -3 11 27.3 54.5 .935
Potassium Chloride
(.0804 N)........- Jan. 19,’09| -6.5 20 25 40 1.315
Potassium Chloride
(.0402 N)........- Jan. 19,’09| -6.5 16 25 37.5 1.195
Ammonium Chloride
(.0804 N)......... Jan. 19,’09) -6.5 11 66.6 66.6 1.005
Ammonium Chloride :
(.0402 N)......... Jan. 19,’09) -6.5 18 11.1 16.7 -935
Potassium Chloride
N) sas vexresis Jan. 19,’09| -6 13 7.7 15.4 1.315
Potassium Chloride
Ni) ezsasargaces Jan. 19,’09| -6 12 0 0 1.195
Ammonium Chloride
(.0804 N)......... Jan. 19,'09) -6 11 0 0 1.005
Ammonium Chloride
(.0402 N)......... Jan. 19,’09) -6 12 0 0 .935
Potassium Chloride
(.0804 N)......... Jan. 21,’09) -4.5 21 61.9 66.6 .93
Potassium Chloride
(.0402 N)......... Jan. 21,'09| -4.5 19 68.4 68.4 92
Ammonium Chloride
(.0804 N)........- Jan. 21,’09]} -4.5 15 86.7 93 995
Ammonium Chloride
(.0402 N)......... Jan, 21,’09} -4.5 19 57.9 63.2 88
Potassium Chloride
(.0804 N)......... Jan. 21,’09) -4 16 0 12.5 .93
Potassium Chloride
(.0402 N)......... Jan. 21,’09) -4 17 17.6 23.5 92
Ammonium Chloride
(.0804 N)......... Jan. 21,’09) -4 17 17.6 23.5 -995
Ammonium Chloride
(.0402 N)......... Jan. 21,’09| -4 16 37.5 50 88
Potassium Chloride
(.0804 N)......... Feb. 2,09) -5 10 0 50 1.49
Potassium Chloride
0402 N)......... Feb. 2,’09| -5 9 11.1 66.7 1.143
Ammonium Chloride
IN)iscauuicnce Feb. 2,09] -5 11 0 54.5 1.17
Ammonium Chloride
(.0402 N)......... Feb. 2,09) -5 13 30.8 38.5 1.325
Potassium Chloride (.0804N), average........... 29.6 51.3 1.238
Potassium Chloride (.0402N), average........... 34.3 58.9 1.091
Ammonium Chloride (oeoaN average..........| 42.6 64.1 1.037
Ammonium Chloride (.0402N), average.......... 46.3 65.8 -969

 

 

 

 
23

It will be seen from these tables that by taking an average of a
large number of these freezings, the percentage of killing is uniformly
lower when the depression is increased.

Shaded Zea Mays seedlings were watered with .0804 N potas-
sium chloride, and others with water with results as follows:

TABLE 2. SHOWING EFFECT OF WATERING WITH MINERAL SOLU-
TIONS ON SAP DENSITY AND HARDINESS OF SHADED
ZEA Mays PtantTs.

 

 

 

 

 

 

 

Percent-
Number |Percent-| age
Watered Date Tem- 0 age Killed | Depres-
With pera- | Plants | Killed and sion
ture Partly
Killed
Potassium Chloride
(.0804 N) .|Feb. 2,’09) -3 18 5.6 5.6 .93
Water —aswses Feb. 2,’09) -3 17 17.6 17.6 -835
Potassium Chloride
(.0804 N) .|Feb. 2,’09) —5 17. 41.2 58.8 93
Water sd... . ss Feb. 2,’09) -5 14 78.6 78.6 835
Potassium Chloride
(.0804 N) .|Feb. 2,’09} -5 14 64.3 85.7 93
Water s,s se Feb. 2,'09} —5 15 80 80 - 833
Potassium Chloride
(.0804 N) .|Feb. 12,’09] -5 8 12.5 50 1.22
Water sd... . Feb. 12,’09] -5 7 57.1 71.4 .65
Potassium Chloride
(.0804 N) -|Feb. 12,709} -4.5 8 50 75 1.22
Water sia... . Feb. 12,’09| -4.5 9 100 100 .653
Potassium Chloride (.0804N), average .......... 34.7 55.0 1.046
WALGER, AVETASE cde cial ccese aye 6! ples arene: syaceia-eudie ween 66.7 69.5 761

 

 

 

The following table gives results of freezing cowpea seedlings
that had been watered with solutions containing 6.03% normal
potassium chloride, sodium chloride, magnesium chloride, ammonium
chloride, sodium nitrate, and distilled water.
24,

TABLE 3. EFFECT OF WATERING WITH MINERAL SOLUTIONS ON
Sap DENSITY AND HARDINESS OF COWPEAS.

 

 

 

 

 

 

 

 
 
 

 

 

 

Percent-
Percent-| age
Watered Date Tem-|Number| age Killed | De-
With pera- | Leaves | Killed and pres-
ture Partly sion
Killed
Potassium Chloride....|June 29,’11| -3.5 35 45.71 57.14 | 1.05
Sodium Chloride...... June 29,’11) -3.5 35 28.57 48.57 | 1.065
Magnesium Chloride..|June 29,'11 -3.5 33 69.69 | 100.00 .975
Ammonium Chloride...|June 29,’11) -3.5 33 3.03 15.15 | 1.035
Sodium Nitrate....... June 29,’11] -3.5 33 9.09 33.33 | 1.05
Distilled Water........ June 29,'11) -3.5 40 77.50 77.50 825
Potassium Chloride....|June 29,11) -3.5 30 56.66 70.00 | 1.05
Sodium Chloride...... June 29,’11) -3.5 36 30.55 38.88 | 1.065
Magnesium Chloride.. .|June 29,’11] -3.5 36 66.66 77.77 .975
Ammonium Chloride...!June 29,’11) -3.5 29 58.62 75.86 | 1.036
Sodium Nitrate....... June 29,’11| -3.5 24: 70.83 79.16 | 1.05
Distilled Water........ June 29,'11) -3.5 36 91.66 | 97.22 825
Potassium Chloride....|July 18,’11] -3 21 33.33 42.85 | 1.13
Sodium Chloride...... July 18,'11) -3 22 36.36 | 54.54 | 1.17
Magnesium Chloride...|July 18,’11] -3 30 85.33 | 100.00 | 1.00
Ammonium Chloride...|July 18,’11} -3 12 83.33 91.66 | 1.155
Sodium Nitrate....... July 18,’11) -3 12 0.0 41.66 | 1.23
Distilled Water........ July 18,’11) -3 30 90.00 | 100.00 .78
Potassium Chloride....|July 19,’11) -2.75 12 100.00 | 100.00 | 1.13
Sodium Chloride...... July 19,'11} -2°75 12 66.66 | 66.66 | 1.17
Magnesium Chloride.. .|July 19,’11) -2.75 29 93.10 | 100.00 | 1.00
Ammonium Chloride...|July 19,’11] -2.75 12 83.33 | 100.00 | 1.155
Sodium Nitrate....... July 19,'11} -2.75 12 0.0 §8.33 | 1.23
Distilled Water........ July 19,’11] -2.75| 30 76.66 | 83.33 78
Potassium Chloride....|July 20,’11) -2.75 12 16.66 58.33 | 1.13
Sodium Chloride...... July 20,'11| -2.75 12 8.33 33.33 | 1.17
Magnesium Chloride...|July 20,’11) -2.75 12 58.33 75.00 | 1.00
Ammonium Chloride...|July 20,’11| -2.75 12 16.66 50.00 | 1.155
Sodium Nitrate....... July 20,’11) -2.75 12 58.33 83.33 | 1.23
Distilled Water........ July 20,'11] -2.75 30 80.00 93.33 78
Potassium Chloride....|July 21,711) -2.75 12 8.33 16.66 | 1.13
Sodium Chloride...... July 21,'11) -2.75 12 0.00 8.33 | 1.17
Magnesium Chloride...|July 21,’11) -2.75 13 15.39 | 30.77 | 1.00
Ammonium Chloride...|July 21,’11] -2.75 12 8.33 16.66 | 1.155
Sodium Nitrate....... July 21,’11) -2.75 12 16.66 16.66 | 1.23
Distilled Water........ July 21,11) -2.75} 30 86.66 | 93.33 78
Potassium Chloride, average........-..-.eseeeees 43.45 | 57.49 | 1.10
Sodium Chloride, average............5ceeeeee cues 28.41 | 41.72 | 1.135
Magnesium Chloride, average 64.75 80.59 .991
Ammonium Chloride, average 33.05 58.22 | 1.115
Sodium Nitrate, average 25.82 52.08 | 1.17.
Distilled Water, average 83.73 | 90.78 795

 
25

It may be said, however, that the solutions all reduced the
growth of the plants, as indicated by the following weights:

Average weight of plants watered with Potassium Chloride........ 2.27 grams
Average weight of plants watered with Sodium Chloride.......... 1.89 grams
Average weight of plants watered with Magnesium Chloride....... 2.33 grams
Average weight of plants watered with Ammonium Chloride....... 1.78 grams
Average weight of plants watered with Sodium Nitrate........... 1.68 grams
Average weight of plants watered with Distilled Water............ 2.63 grams

The percentage of killing will thus be seen to be as much in
proportion to growth as in inverse proportion to depression.

Corn seedlings were also grown where water was withheld,
being watered only when it was necessary to keep them from dying.
The following table gives the results:

TABLE 4. SHOWING EFFECT OF WITHHOLDING WATER ON SAP DEN-
SITY AND HARDINESS OF ZEA Mays.

 

 

 

 

 

 

Percent-
Percent-| age

Treatment Date Tem-|Number| age Killed | De-

pera- | Plants | Killed and pres-

ture Partly | sion

Killed

Well watered.......... Feb. 2,'09} -4 13 84.6 92.3 -785

Water withheld....... Feb. 2,’09) -4 10 0.0 40. 1.07
Well watered.......... Feb. 2,’09} -5 13 61.5 74.6 . 835

Water withheld....... Feb. 2,09] —-5 5 20.0 80.0 1.07
Well watered.......... Feb. 2,’09| -5.5 12 66.7 100.0 .835

Water withheld....... Feb. 2,'09| -5.5 6 16.7 50.0 1.07

Well watered.......... Feb. 12,’09} -4.5 10 60.0 60.0 71
Water withheld....... Feb. 12,’09| -4.5 9 44.5 44.5 1.085
Well watered, average. ........ 00 cc cee ccc ceecenee 68.19 | 81.72 «791
Water partially withheld, average................. 20.27 53.60 | 1.074

 

 

 

 

It will be seen again that withholding water increased the sap
density (depression) and lowered the killing temperature. It also
reduced the rate of growth and probably the size of the cells, so we
can not conclude with certainty that the greater hardiness is due only
to the greater sap density.

Tomatoes were grown in the same way except that there were
three lots—some well watered, others watered only when it was
necessary to keep them from dying, and some others grown outside
at a temperature considerably lower than that in the greenhouse.
The following table gives the results:
26

TABLE 5. SHOWING EFFECT OF CONDITION OF GROWTH ON SAP
DENSITY AND HARDINESS OF TOMATOES.

 

Tem- | Number : De-
Treatment Date pera- of Result of Freezing pres-
ture | Plants sion

 

Out of ‘doors....jApr. 29,’11] -2 AML dea di cnicsesece eacie eoaie 0.73
Greenhouse, wet/Apr. 29,’11] —2 Leaves all dead; stems
slightly injured...... 0.84
Greenhouse, dry|Apr. 29,’11| ~—2 Uninjured except very
young leaves......... 1.16
Out of doors....|May 2,’11] -2 At dead (larger and
stockier)............ 73
Greenhouse, wet|May 2,’11) -2 Leaves dead; lower |
stems alive.......... 0.84

Greenhouse, dry/May 2,'11} -2 Only few leaves killed ; 1.16

FP PF PE PRP Pe PR RR

Out of doors....|May 4,11] -2.5 Foliage and upper one-

third stems killed....| 0.73
Greenhouse, wet/May 4,’11] -2.5 All killed.............. 0,84
Greenhouse, dry|May 4,'11| -2.5 Leaves killed; stems un-

injured.............. 1.16
Out of doors....|May 6,711] -2.5 Leaves killed ; stems un-

injured.............. 73
Greenhouse, wet|May 6,’11] -2.5 Leaves dead; upper one-

third stems dead..... 0.84
Greenhouse, dry|May 6,’11| -2.5 Foliage and growing

tips of three plants
dead; one plant un-
injured Ao tawe eae 1.16

 

 

 

 

 

 

Contrary to what might be expected, those tomato plants grown
in the greenhouse but watered sparingly were more hardy than those
grown outside; also the depression was greater. The results in this
table again indicate that as the depression is lowered, plants are made
more hardy.

Cabbage, kale and turnips were each grown in the greenhouse
some watered well and others with water withheld except when it
was necessary to keep the plants alive, while others were grown out
of doors. The following table give results, and depressions for these
plants.
TABLE 6. SHOWING INFLUENCE OF CONDITION OF GROWTH ON SAP
DENSITY AND HARDINESS.

 

 

   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Percent-
Tem- |Number |Percent-| age De-
Treatment Date pera- of age Killed | pres-
ture | Leaves | Killed and sion
Partly

CABBAGE Killed
Out of doors...... 3 0 0
Greenhouse, dry...... 3 0 0
Greenhouse, wet....... 3 33.4 33.4
Out of doors.......... 3 0 0
Greenhouse, dry....... 3 0 0
Greenhouse, wet....... 3 66.7 66.7
Out of doors.......... 4 0 0
Greenhouse, dry....... 5 100 100
Greenhouse, wet....... 5 100 100
Out of doors.......... 4 0 0 .
Greenhouse, dry....... 4 100 100 s
Greenhouse, wet....... 4 100 100 <
Out of doors.......... 4 0 0
Greenhouse, dry....... 4 100 100
Greenhouse, wet....... 4 100 100 acne
Out of doors.......... 3 0 0 1.18
Greenhouse, dry....... 3 0 0 -90
Greenhouse, wet 2 100 100 .99
Out of doors, average.......... ec cee cece eee cence 0 0
Greenhouse, dry; average...........cc cee e ec eeee 50 50
Greenhouse, wet; average..............0eeeeceeee 83.3 83.3

TURNIPS
Out of doors.......... Nov. 2,’11] -5.5 3 0 100
Greenhouse, dry.......|Nov. 2,’11) -5.5 3 100 100
Greenhouse, wet.......|Nov. 2,’11] -5.5 3 100 100
Out of doors.......... Nov. 4,’11} -6 3 0 0
Greenhouse, dry....... Nov. 4,11] -6 3 100 100
Greenhouse, wet....... Nov. 4,’11} -6 3 100 100

KALE

Out of doors, coldframe|Dec. 8,11} -6.5 2 50 50 é
Out of doors, bed...... Dec. 8,’11] -6.5 3 0 0 s
Greenhouse, dry....... Dec. 8,’11} -6.5 3 100 100
Greenhouse, wet....... Dec. 8,’11} -6.5 3 100 100 ‘

LETTUCE
Out of doors.......... Mar. 9,’13} -3.5 8 0 25 .900
Greenhouse........... Mar. 9,713] -3.5 9 83.3 100.0 -867
Out of doors.......... Mar, 29,’13) -5 18 0 27.7 -900
Greenhousge...........- Mar, 29,13] -5 16 68.7 93.7 -867
Out of doors.......... Apr. 30,13} -3.5 24 0 33.3 920
Greenhouse........... Apr. 30,’13] -3.5 32 18 48 .740
Average, lettuce out of doors......-......0eeee0e- 0.0 28.7 -907
Average, lettuce greenhouse................020005 56.6 80.1 825

 

 
28

Depressions were not determined for each day’s freezing on
account of the limited number of plants, but depressions taken of
other lots grown under the same conditions show similar results.
Thus a set taken January 6, 1912, showed the following depressions:
Plants grown out of doors, depression, 1.470; plants grown in the
greenhouse with limited water supply, depression, 1.035; plants
grown in the greenhouse with abundant water supply, depression,
990. Here again increased sap density is accompanied by greater
hardiness, and in this case the plants with the greatest density are
also the ones which grew most rapidly.

In all of these cases any treatments that increased the density
of the sap lowered the killing temperature. It should be said, how-
ever, that in most cases where the density of the sap has been in-
creased, the growth of the plants has been checked so we can not say
positively that a treatment has increased the hardiness, due to the
density of the sap, since it could probably be due to the smaller cells
or some other differences in the conditions of the protoplasm. How-
ever, cabbage and kale were exceptions to this and actually grew
more rapidly out of doors and yet had more dense sap and were more
hardy. In order to test the effect of increased sap density on hardi-
ness under conditions where this effect on growth would be elimi-
nated, plants of tomato, cabbage, lettuce, kale and cowpeas were
grown under like conditions. Then the plants were pulled, the roots
washed clean and placed in sugar solutions and in potassium chlo-
ride and other solutions of varying strengths as shown in the table,
with the results to be seen in the following table.
29

TaBLE 7. SHOWING INFLUENCE OF ABSORBED SOLUTIONS ON

 

 

 

 

 

 

 

 

 

 

HARDINESS.
Percent-
Roots 24 hrs. in solu- Tem- | Number |Percent-| age De-
tions of strength meas- Date pera- of age Killed pres-
ured by freezing points ture | Leaves | Killed and sion
given below Partly
Killed
TOMATOES
Glucose (.460)......... July 27,11} -3.0 84 63.0 67.6 | 0.785
Cane Sugar (.435)..... July 27,’11) -3.0 60 83.3 88.3 | 0.925
Glycerine (.430)....... July 27,11] -3.0 70 72.8 88.5 1.070
Potassium Nitrate
CE6s) a hcusehageereeaaceds July 27,’11) -3.0 57 100.0 100.0 | 0.880
Wate tis iviii-.0s cinco July 27,'11} -3.0 65 100.0 100.0 0.700
Cae (.460)........ . July 27,11) -2.0 60 0.0 0.0 | 0.785
Cane Sugar (.435)..... July 27,'11} -2.0 57 24.5 56.1 | 0.925
Glycerine (.430)....... July 27,711) -2.0 44 50.0 53.6 1.070
Potassium Nitrate
po ieee Rae wee July 27,'11) -2.0 46 60.8 73.9 | 0.880
Wateticics ss 2eesanees July 27,’11] -2.0 48 62.5 72.9 | 0.700
Dieu (.460)......... July 28,'11) -3.5 48 91.6 95.8 | 0.785
Cane Sugar (.435)..... July 28,’11) -3.5 47 89.3 95.7 0.925
Glycerine (.430)....... July 28,11) -3.5 55 94.5 100.0 1.070
Potassium Nitrate
CAG3)icesdussatonvceuareeionate July 28,'11| -3.5 53 98.1 100.0 | 0.880
Waters ic.icues cae ce July 28,’11} -3.5 43 76.7 100.0 | 0.70
Glucose (.460)......... July 28,’11) -2.5 47 59.5 70.0 | 0.785
Cane Sugar (.435)..... July 28,'11} -2.5 58 13.8 17.2 0.925
Glycerine (.430)....... July 28,’11] -2.5 52 9.6 44.2 1.070
Potassium Nitrate
OB )iccscicirersssiiestass eae July 28,'11) -2.5 43 83.7 100.0 | 0.880
Watenviaec scorminearsees July 28,’11} -2.5 42 11.9 16.6 | 0.700
Guiane (£460) wos. ac.aasus July 28,’11| -3 33 69.7 69.7 0.785
Cane Sugar (.435)..... July 28,’11} -3 37 18.9 35.1 0.925
Glycerine (.430)....... July 28,11} -3 44 61.3 61.3 1.070
Potassium Nitrate
63) iwercnm sc vas ee July 28,’11| -3 46 100.0 100.0 | 0.880
Watefrie.sisencsacsae July 28,’11| -3 42 66.6 66.6 | 0.700
Glucose (.460), average......... 2. eee eee eee eee 56.8 60.6 | 0.785
Cane Sugar (.435), average......... 0. cece eee eens 45.9 58.5 | 0.925
Glycerine (.430), average.......... 0. eee e eee eeeee 57.6 69.5 1.070
Potassium Nitrate (.463), average...............-- 88.5 94.6 0.880
Water, average........... 63.5 71.2 | 0.700

 
30

 

 

 

 

 

 

 

 

 

 

Percent-
Roots 24 hrs. in solu- Tem-|Number |Percent-| age De-
tions of strength meas- Date pera- of age Killed | pres-
ured by freezing points ture | Leaves | Killed end sion
; artly
given below Killed
TOMATOES
Treated 18 hrs.
Watenivcciexedca cies June 28,'13) -2.5 20 ! 50.0 65.0 -698
Potassium Chloride
MLD) ied wa tmacs shea irs June 28,'13} -2.5 19 0.0 0.0 1.103
Ammonium Chloride
3900) es ees ce eee as June 28,’13} -2.5 15 66.7 93.3 . 863
Glycerine (2.820)...... June 28,113] -2.5 27 0.0 0.0 | 2.083
ACCT ica set cane quand ones June 28,’13} -3.0 16 100.0 100.0 -698
Potassium Chloride
WED assitee sclse aed wave June 28,'13) -3.0 17 0.0 35.3 1.103
Ammonium Chloride
SOQ) irs owt wane 'oeaes une 28,13} -3.0 16 68.7 77.4 863
Cane Sugar (.677)..... June 28,'13} -3.0 30 53.3 76.6 1.053
CABBAGE
Cane Sugar (0.77)..... Aug. 24,’11) -4.0 3 100.0 | 100.0 | 1.230
Glucose (0.44)......... Aug. 24,’11] -4.0 3 100.0 100.0 1.190
Glycerine (0.66)....... Aug. 24,11] -4.0 3 66.6 66.6 1.270
Potassium Chloride
Moy seataia sacra eiscclee eae Aug. 24,’11| -4.0 3 0.0 0.0 1.525
Ammonium Chloride
jeawitie me mae she Aug. 24,11] -4.0 3 100.0 100.0 1.195
Water’ sins ese scisoies ves Aug. 24,11] -4.0 3 66.6 66.6 1.080
Cane Sugar (0.77)..... Aug. 26,’11} -3.5 3 66.6 66.6 1.230
Glucose (0.44)......... Aug. 26,’11] -3.5 3 66.6 66.6 1.190
Glycerine (0.66)....... Aug. 26,’11} -3.5 3 66.6 66.6 1.270
Potassium Chloride
NUD) osssestcack ave 'e rane Aug. 26,’11) -3.5 3 0.0 0.0 1.525
Ammonium Chloride
(O51 iaisataer sone a atere Sie: ug. 26,711] -3.5 3 100.0 100.0 1.195
Water. cases sacce ves Aug. 26,’11] -3.5 3 100.0 100.0 1.080
Cane Sugar (0.77)..... Aug. 31,’11] -5.5 3 66.6 66.6 1.230
Glucose (0.44)......... Aug. 31,’11) -5.5 3 33.3 33.3 1.190
Glycerine (0.66)......./Aug. 31,'11] -5.5 3 0.0 0.0 | 1.270
Potassium Chloride
0573) scotia ee weet e Aug. 31,’11) -5.5 3 0.0 0.0 1.525
Ammonium Chloride
(ORS 1) sasigendenraceveteoca i Aug. 31,’11} -5.5 3 66.6 66.6 1.195
Waterisccskenccaacscie ca Aug. 31,’11] -5.5 3 0.0 0.0 1.080
Cane Sugar (0.77), average............c cece ce eeee 77.7 77,7 1.230
Glucose (0.44), average........ ccc cece eee ences 66.6 66.6 1.190
Glycerine (0.66), average..........0.cc cece ee eee 44.4 44.4 1.270
Potassium Chloride (0.73), average................ 0.0 0.0 1,525
_Ammonium Chloride (0.51), average.............. 88.8 88.8 1.195
Water, average... . ec cc cece cece eee en neces 55.5 55.5 1.080

 
31

 

 

 

     

 

 

 

 

Percent-
Roots 24 hrs. in solu- Tem-|Number|Percent-| age De-
tions of strength meas- Date pera- of Age Killed | pres-
ured by freezing points ture | Leaves | Killed and sion
given below Partly
Killed
CABBAGE
(later freezing)
No treatment......... July 1,'13} -4.0 5 80.0 | 100.0 . 780
Potassium Chloride
CUTS) sss cccavayaineca: iene: avons July 1,'13) -4.0 5 40.0 100.0 1.145
Glycerine (2.82)....... qu 1,713] -4.0 5 20.0 80.0 1.780
Ammonium Chloride
(360) sctcewesrsie sew eiete July 1,713) -4.0 5 100.0 100.0 -950
COWPEAS
Cane Sugar (1.570)....|Sept. 1,’11} -3.0 3 0.0 0.0 | 1.230
Glucose (1.740)........ Sept. 1,’11) -3.0 3 100.0 100.0 1.250
Glycerine (1.575)...... Sept. 1,’11] -3.0 3 0.0 0.0 1.160
Potassium Chloride
(0:730) cssoeces seve Sept. 1,’11] -3.0 3 100.0 100.0 1.130
Ammonium Chloride
he pelate aiexsenciaiate Sept. 1,’11} -3.0 3 66.6 66.6 1.140
Water... ...ccesccncees Sept. 1,’11] -3.0 3 33.3 33.3 .870
Cane Buzar (1.570)....|Sept. 9,’11] -3.0 3 0.0 0.0 1.230
Glucose (1.740)........ Sept. 9,’11] -3.0 3 33.3 66.6 1.250
Glycerine (1.575)...... Sept. 9,11] -3.0 3 0.0 0.0 1.160
Potassium Chloride
(0.730)......200200e Sept. 9,’11! -3.0 3 0.0 0.0 1.130
Ammonium Chloride
5) 9 -3.0 3 33.3 100.0 1.140
é 9, -3.0 3 100.0 100.0 .870
Cane Sugar (1.570).... 9, -3.5 3 0.0 0.0 1.230
Glucose (1.740)........ -3.5 3 66.6 66.6 1.250
Glycerine (1.575)...... -3.5 3 0.0 0.0 1.160
Potassium Chloride
(0.730) iS 3 66.6 66.6 1.130
Ammonium Chloride
(0.725)... s iS 3 66.6 66.6 1.140
Water Sept -5 3 33.3 33.3 .870
Cane Sugar (1.570)... .|Aug. 29,11) -3 3 0.0 0.0 | 1.230
Glucose (1.740)........ Aug. 29,’11) -3 3 0.0 0.0 1.250
Glycerine (1.575)...... Aug. 29,’11] -3 3 0.0 0.0 1.160
Potassium Chloride
(0.730)..........00- Aug. 29,’11] -3.0 3 100.0 100.0 1.130
Ammonium Chloride
(O0925) wiecies cpecpsieseess Aug. 29,11] -3.0 3 0.0 0.0 1.140
Watefesncdsicaianasies Aug. 29,'11| -3.0 3 100.0 100.0 .870
Cane Sugar (1.570), average...........eceeee eens 0.0 0.0 | 1.230
Glucose (1.740), average.......... cece cece eee eeee 49.9 58.3 1.250
Glycerine (1.575), average... .. cece cect ence ence 0.0 0.0 1.160
Potassium Chloride (0.730), average.............4- 66.6 66.6 1.130
Ammonium Chloride (0.725), average............. 41.6 58.3 1.140
Water, average.......cce eee e cee s een crecccesces 66.6 66.6 .870

 

 

 

 
 

 

 

Percent-
Roots 24 hrs. in solu- Tem- |Num-|Percent-| age De-
tions of strength meas- Date pera- |ber of} age Killed | pres-
ured by freezing points ture |Leaves} Killed oe sion
iven below artly
oe Killed
Percent-
age total
KALE leaf
surface
killed
Cane Sugar (.677)..... June 25,’13] -3.0 5 0.0 45.0 947
Glycerine (2.820)...... June 25,’13] -3.0 5 20.0 35.0 1.595
Potassium Chloride
BD) enscmarewdos wae June 25,’13] -3.0 5 60.0 80.0 -967
Ammonium Chloride
(B60) sided sanesoiarace atais June 25,’13| -3.0 5 80.0 95.0 175
WateP so ieccc tin acccacnscigoee June 25, ao -3.0 5 80.0 93.0 .677
Cane agar (.677)..... July 9)" -1.5 5 40.0 45.0 | 1.150
Glycerine (2.820)...... July 9 43 -1.5 5 0.0 10.0 | 1.980
Potassium Chloride
(PTS) deco ntessmeaies July 9,'13] -1.5 5 0.0 20.0 -980
Ammonium Chloride
66360) sas cosieictwiea a July 9,13) -1.5 5 60.0 80.0 895
Wate ies ie.sc0resSesine cand. sievees July 9,'13} -1.5 5 60.0 75.0 830
LETTUCE
Cane Sugar (.677)..... July 13] -2.5 5 0.0 35.0 578
Glycerine (2.820)...... July 2,’13) -2.5 5 0.0 30.0 | 1.168
Potassium Chloride
BLO) eaetaais tw sates July 2,13) -2.5 5 20.0 60.0 -655
Ammonium Chloride
C360) ie isoecue cosas sence July 2,'13} -2.5 5 40.0 70.0 .550
Wt 5 cccaveensnepee des July 2,'13] -2.5 5 40.0 90.0 .430
Cane Sugar (.677)..... July 2,13) -3.5 5 20.0 85.0 578
Glycerine (2.820)...... July 2,713) -3.5 5 0.0 55.0 1.168
Potassium Chloride '
AED) is ace seanclea crate sai July 2,13) -3.5 5 40.0 65.0 655
Ammonium Chloride
Ane Rates See EES July 2,'13) -3.5 5 60.0 90.0 .550
Water: sccaceviaweans July 2,13} -3.5 5 60.0 90.0 430
Cane Bier (.677)..... July 8,'13} -3.0 5 0.0 25.0 .652
Glycerine (2.820)......|July 8,13} -3.0 5 0.0 35.0 128
Potassium Chloride
RUM O)  ecorsutuhid Arica ealiters July 8,’13} -3.0 5 0.0 55.0 690
Ammonium Chloride
(360 ins cides woe selarsca July 8,’13} -3.0 5 60.0 90.0 690
Water............0005 July 8,’13} -3.0 5 20.0 65.0 597

 

 

 

 

 

 

 
33

Here again the hardiness has been increased by increasing the
density of the sap. Of course it should be admitted that even here
there is a possibility that some actual change in the protoplasm has
taken place by treating it with these solutions. Glycerine has been
most effective in increasing the sap density of the tissue and in in-
creasing the resistance to cold. It is interesting to observe that in
the case of cabbage, the sap density and the hardiness were more
greatly increased with salts like potassium chloride than with cane
sugar, while in the case of tomatoes, sugar was taken up in larger
quantities and caused a greater increase in hardiness.

According to the theory of Gorke, if killing is due to the salt-
ing out of proteids, we should expect the taking up of sugar to increase
the hardiness but should not expect that result to follow the taking
up of salts. The salts that most readily precipitate certain proteids
are ammonium sulphate and zinc sulphate. When roots of tomato
plants were kept for twenty-four hours in solutions of a molecular
concentration as great as those used in the table above, the hardi-
ness of the leaves was not reduced, and zinc sulphate seemed to in-
crease the hardiness. These results are not in accord with Gorke’s
theory. Potassium nitrate does not increase the hardiness as other
substances do. Thus tomato plants with their roots kept in potas-
sium nitrate solution of about the same molecular concentration as
the solutions used above, seemed to be killed more easily than when
the roots were kept in pure water, and corn plants so treated cer-
tainly were killed more easily. This lack of protective action is
probably due to the high eutectic point of the potassium nitrate
since it would precipitate out before the killing temperature of the
tissue is reached.

Apple and peach blossoms were cut from the twigs in such a
way that a considerable area of cortex and sap wood adhered to the
stem, and these were inserted in solutions of varying strengths of
sugar and glycerine and later frozen. The following table gives the
results:

i)
34

TABLE 8. SHOWING INFLUENCE OF ABSORBED SOLUTIONS ON Har-
DINESS OF YOUNG FRUITS.

 

 

 

 

 

 

 

Tem- | Number |Percent-
Kind of Fruit Treatment Date pera- of age
ture Fruits | Killed
Rice’s Seedling peach
blossoms............ Fresh.... |Apr. 15,11) ~3 43 70.0
Rice’s Seedling peach | Cane sugar
blossoms ........... (2.250)..... Apr. 15,’11] -3 34 3.0
Rice’s Seedling peach | Glycerine
blossoms............ (2.560)....JApr. 15,’11] -3 45 22.0
Rice’s Seedling peach
blossoms............ Water...... Apr. 15,’11] -3 50 100.0
Rice’s Seedling peach | Cane sugar
blossoms............ (2.250)....]Apr. 20,’11] -3 13 61.0
Rice’s Seedling peach | Glycerine
blossoms............ (2.560)..../Apr. 20,’11] -3 22 36.0
Rice’s Seedling peach :
blossoms............ Water...... Apr. 20,711} -3 15 66.0
Rice’s Seedling peach
blossoms, petals just | Cane sugar
fallen........ a apdizeain (2.250)....|Apr. 20,’11) -~3 24 81.0
Rice’s Seedling peach
blossoms, petals just | Glycerine
AMER soi ccce ae es oes (2.560)....|Apr. 20,711} -3 21 81.0
Rice’s Seedling peach
blossoms, petals just
fallen............... Water...... Apr. 20,’11) -3 13 58.0
Peaches in husk........ Fresh .|May 4,'11) -3 a 12.2
Peaches in husk........ Cane sugar
(2,250)....|May 4,’11] -3 8.7
Peaches in husk........ Glycerine
(2.560)....;May 4,’11) -3 6.0
Peaches in husk........ Water...... May 4,'11| -3 is 70.0
Peaches 2-5 in. in dia. | Fresh...... May 11,’11| -3.9 21 24.0
Peaches 2-5 in. in dia, | Cane sugar
(2.250)....]May 11,’11] -3.9 20 35.0
Peaches 2-5 in. in dia. qraaee
2.560)....|May 11,’11] -3.9 25 ;
Peaches 2-5 in. in dia. ao May 11,’11] -3.9 18 38.0
Apple buds showing Co
PUT ocis sWatee ga ae pega 2.250)..../Apr. 24,’11] -3 31 .0
Apple buds showing Clyeerin 7 e
DINK es g.00 ues Qrexan 2.560)....JApr. 24,’11} -3 :
Apple buds showing ) R o rn
Pinks. cess wies nee one Water...... Apr. 24,’11]  -3 25 :
Apple buds nearly open | Fresh...... Apr. 24711 -3 30 100.0
Apple buds nearly open ne sugar s
2.250)....|Apr. 24,’11] ~3 s
Apple buds nearly open Glycerine . , a ae
2.560)....jApr. 24,’11] -3 :
Apple buds nearly open | Water. ! Sates Ape. 24°11 -3 a 1000
Apple buds partly open as sugar
2.250)....|/Apr. 26,111] ~-3 34 3.0
Apple buds partly open | Glycerine RB 26,'11
(2.560)... -3 34 61.0

 
35

 

 

 

 

 

 

 

Tem- | Number |Percent-
Kind of Fruit Treatment Date pera- of age
ture Fruits | Killed
Apple buds partly open | Water...... Apr. 26,11) -3 23 100.0
Apple blossoms open...| Fresh........|Apr. 26,’11) -3 27 4.0
Apple blossoms open...| Cane sugar
(2.250)....|Apr. 26,711] -3 50 0.0
Apple blossoms open. ..| Glycerine
(2.560)....jApr. 26,’11]) -3 50 14.0
Apple blossoms open...} Water...... Apr. 26,’11) -3 37 92.0
Apple blossoms, petals
just fallen........... Fresh....... May 4,’11) -3 28 36.0
Apple blossoms, petals | Cane sugar
just fallen........... (2.250)....|May 4,’11] -3 50 .0
Apple blossoms, petals | Glycerine
just fallen........... (2.560)....]May 4,’11) -3 44 4.0
Apple blossoms, petals
just fallen........... Water...... May 4,'11) -3 43 72.0
Apples just after petals
fall isis tesa caine xis eee Fresh...... May 11,’11) -3.9 58 35.0
Apples just after petals | Cane queer
fall owccici cs agiesicescis (2.250)....|May 11,11) -3.9 83 9.6
Apples just after petals Glycerine |
falls causa consgieadins (2.560)....|May 11,’11) -3.9 76 3.0
Apples just after petals
diamante xan 4 sie 6 RY Water....../May 11,’11) -3.9 66 79.0
Apples 1-3 in. in dia....] Fresh....... May 11,’11| -3.9 17 41.0
Apples 1-3 in. in dia....| Cane ad
: (2.250)..../May 11,11) -3.9 27 20.0
Apples 1-3 in. in dia.... Glycerine”
(2.560)..../May 11,’'11} -3.9 31 6.4
Apples 1-3 in. in dia....} Water...... May 11,’11) -3.9 28 100.0
Wild Goose plums...... Cane sugar
(2.250)....)/May 11,’11}. -3.9 25 4.0
Wild Goose plums...... Glycerine
(2.560)....|May 11,’11) -3.9 25 0.0
Wild Goose plums...... Water...... May 11,'11]) -3.9 21 16.0
pee Gane sugar (2:50) sa o-syee eng tignee s oo Guha owe fers a eure eres as 26.9
Average, Glycerine (2.560)....... cece cece cece cen eer ee ee eenes 9.2
Average’, Wateran snes s as-cars ate se tee fone bale vale le BE oe aw Eunos oa ee 75.9

 

 

It will be seen again that absorbing the solutions increased the
resistance to cold. Depressions were not taken because it would
require too many fruits treated in this way. However, it is safe
to assume that the sap density was increased as it certainly was with
the fruits used for the next table.

During the spring of 1913, twigs containing peaches, apples
and cherries were placed with the ends in glvcerine solution, sugar
solution and in pure water.

36

These fruits absorbed the solutions

readily as the depression data following the table will show. The
following table gives the result of freezing these fruits:

TABLE 9. SHOWING EFFECT OF ABSORBED SOLUTIONS ON HAarpI-
NESS OF BLOSSOMS AND YOUNG FRUITS ON TwiIGs.

 

 

Tem- | Number |Percent-
Kind of Fruit Treatment Date Pere _ of : wetei
ure ruits e
Twigs containing very
young Rareripe | Water
peaches.............. 23 brs......|Apr. 28,’13] -5 56 55.3
Twigs containing very | 20% Cane
young Rareripe | sugar
peaches............- 23 hrs......|Apr. 28,713} —-5 77 29.7
Twigs containing very | 10%
young Rareripe | Glycerine
peaches............. hrs......|Apr. 28,'13]  -5 51 11.8
Twigs containing very
young Rareripe | Fresh from
peachesenciu. sci cous trOC wicie ese Apr. 28,’13) -5 69 49.3
Twigs _ containing | 10%
young Hiley | Glycerine
peaches............. 20 hrs......|May 1,'13) -4 65 1.5
Twigs containing | Fresh from
young Hiley peaches | tree....... May 1,'13| -4 76 1.3
Twigs containing | Water
Lewis peaches....... 21 hrs......|May 17,'13 22 45.5
Twigs containing | 10%
Lewis Glycerine
peaches............. 21 hrs....../May 17,'13} -4 35 11.4
Twigs containing | Wilted
Lewis peaches....... 6 hrs. -|May 17,713) -4 22 45.5
Twigs containing | Fresh from
Lewis peaches....... trees sneews May 17,13] -4 23 43.5
Twigs containing | 10%
Bernard Glycerine
peaches............. 22 hrs. .|May 21,713) -4.2 51 13.7
Twigs _ containing | Wilted
Bernard peaches..... 5 hrs.......(May 21,’13' -4.2 53 69.8
Twigs _ containing | Fresh from
Bernard peaches..... tree....... May 21,'13) -4.2 34 61.8
Twigs containing open | 20% Cane
Rome Beauty apple | sugar solu-
blossoms............ tion 20 hrs.|May 1,'13| -4 96 15.6
Twigs containing open | 10%
Rome Beauty apple Glycerine
blossoms............ 20 hrs......|May 1,'13| -4 108 13.8
Twigs containing open
Rome Beauty apple | Fresh from
blossoms............ TOE! wis esas May 1,'13} -4 83 40.0

 

 

 

 

 

 
37

 

 

 

 

 

 

 

Tem- | Number |Percent-
Kind of Fruit Treatment Date pera- of age
ture Fruits | Killed

Twigs containing | Water

Jonathan apples..... 21 hrs......|May 17,'13} -4 27 70.4
Twigs containing | 10%

Jonathan Glycerine

AP PIES jissivess ccsundaoiaeas hrs......|May 17,'13) -4 32 43.8
Twigs containing | Wilted

Jonathan apples..... 6 hrs.......}May 17,'13} -4 37 86.5
Twigs containing | Fresh from

Jonathan apples..... COC sss verace May 17,'13| -4 19 68.4
Twigs containing | Water

Dyehouse cherries ..| 21 hrs -|May 17,'13) -4 42 30.9
Twigs containing | 10%

Dyehouse Glycerine

cherries...........--: 21 hrs. .'May 17,'13| -4 43 13.9
Twigs containing | Wilted

Dyehouse cherries..'..; 6 hrs.. .|May 17,’13| -4 36 48.8
Twigs containing | Fresh from

Dyehouse cherries....{ tree....... May 17,713) -4 15 66.6
Twigs containing | 10%

Dyehouse Glycerine

cherries............. 22 hrs......|May 21,'13| -4.2 39 5.1
Twigs containing | Wilted

Dyehouse cherries....| _5 hrs.. -|May 21,713} -4.2 56 21.4
Twigs containing | Fresh from

Dyehouse cherries....| trees...... May 21,'13| -4.2 38 39.5
Average percentage killed, fresh........... cece cece cece e eee e eens 48.8
Average percentage killed, glycerine............. cee eee e eee cence 14.4

 

 

Since it requires a large number of blooms or young fruits to
furnish sap for a freezing point determination, only one such deter-
This resulted as follows, using fruits treated
just as they were for freezing:

mination was made.

Cherries fresh from tree

Cherries from twigs with ends in glycerine sixteen hours...
Cherries wilted five hours

Depression
degrees

 

Peaches: fresh from: tree so.sie é-xisre iarece: 3003 0-65 scetiiin nigra ouaiia oe se He eA evar es

Peaches from twigs with ends in glycerine sixteen hours
Peaches wilted five hours
Apples from twigs with ends in glycerine thirty hours

Apples from twigs with ends in water thirty hours

Apples from twigs with ends in cane sugar thirty hours
Apples from twigs with ends in glycerine forty-eight hours
Apples from twigs with ends in water forty-eight hours
Apples from twigs with ends in cane sugar forty-eight hours
38

It seems then practically certain that one is justified in assum-
ing that the fruits in the above freezing table had their osmotic
strength increased as much by taking up the glycerine and sugar
solutions as this depression data indicates. The fruits that had
absorbed the glycerine were apparently fully turgid while the wilted
fruits were very flaccid. It is certain that wilting could have had
little part in increasing the sap density of the fruits absorbing the glyc-
erine. It may be suggested by some that possibly the tissue could
not absorb these rather strong solutions as rapidly as it could absorb
water, so there might be some wilting to cause the greater hardiness
attributed to the increased sap density. Observations were made on
this point in all cases and rarely was there any signs of wilting in the
frozen tissues referred to. In most cases, plants which were wilted
until they were very limp before treating as described above were

still less hardy than those absorbing the solutions. It is thus cer-

tain that the greater hardiness of the tissue absorbing the various
solutions was not due to wilting. The effect of wilting on tissue is
discussed later in this paper.

Reducing Sap Density by Shading. The sap density of leaves
is known to increase from morning to afternoon. Leaves shaded
usually have a lower sap density than those in the light. It was
thought that this would be another good means of testing the effect
of sap density on hardiness. The following plants (or twigs contain-
ing leaves) were shaded for twenty-four hours and taken for freezing
in early afternoon along with plants under similar conditions, ex-
cept that they were in full sunlight. The results are shown in Table
10:

TABLE 10. SHOWING EFFECT OF SHADING ON SAP DENSITY AND
RESISTANCE TO FREEZING.

 

Per-
Per- | cent-
Tem- | Number | cent- | age De-
Material Treatment Date pera- of age | Total | pres-

ture | Plants All Leaf | sion
Killed | Area

 

Killed
Cowpeas...:...|Shaded..../June 14,'13) —4 3 0.0 | 90.0 852
Cowpeas.......|Not shaded|June 14,’13) -4 2 100.0 |100.0 -980
Cowpeas....... Shaded... .|June 14,’13) -3 3 0.0 | 90.0 852
Cowpeas....... Not shaded|June 14,'13] -3 3 0.0 | 22.0 - 980
Cowpeas....... Shaded..../June 17,13] -3 3 66.6 | 66.6 855
Cowpeas....... Not shaded|June 17,’13] -3 4 25.0 | 81.2 947

 

 

 

 

 

 

 

 

Reet
39

 

 

 

Per-
Per- | cent-
; Tem- | Number] cent- | age De-
Material Treatment] Date pera- of age | Total | pres-
ture | Plants | All | Leaf | sion
Killed] Area
Killed
White corn..... Shaded..../June 13,’13| -4 15 ... | 99.0 -728
White corn....|Not shaded|June 13,’13) -4 12 oes | 99:0 888
Cortes vsusexede Shaded... .|June 17,13] -3 7 18.8 | 55.0 835
GOL sieseie seers vets Not shaded|June 17,’13| -3 7 0.0 | 25.0 | 1.035
Tomato leaflets./Shaded....|June 19,'13, -2 34 38.2 | 65.3 . 708
Tomato leaflets.) Not shaded|June 19,’13) —2 51 0.0 0.0 - 848
Tomato leaflets.|/Shaded....|June 19,’13} -3.5 35 100.0 {100.0 . 708
Tomato leaflets.| Not shaded|June 19,’13) -3.5 36 47.2 | 63.9 . 848
Tomato leaves..|Shaded....|/June 25,’13] —4. 6 50.0 | 87.0 .595
Tomato leaves..|Not shaded|June 25,’13] -4 5 40.0 | 55.0 752
Kale leaves.....|/Shaded....|June 25,’13| -3.5 5 100.0 {100.0 - 660
Kale leaves.....|Not shaded|June 25,'13) -3.5 5 40.0 | 70.0 . 790
Lettuce leaves...|Shaded....|June 25,’13) -3.5 6 100.0 /100.0 .490
Lettuce leaves. .|Not shaded|June 25,’13' -3.5 6 100.0 {100.0 .590
Lettuce leaflets. |Shaded....|/June 21,’13] -2.8 13 23.0 | 50.0 .570
Lettuce leaflets.| Not shaded|June 21,’13) -2.8 17 0.0 1.4 . 740
Lettuce leaflets. |Shaded....|June 21,’13] -4 18 100.0 |100.0 -570
Lettuce leaflets.| Not shaded|June 21,13} -4 17 41.1 | 66.1 . 740
Red Rock
Cabbage leaflets|Shaded....|June 20,'13) -—3.5 14 0.0 | 19.6 - 860
Red Rock Cab-
bage leaflets..;Not shaded|June 20,13} -3.5 14 7.1 7.1 £955
Red Rock Cab-
bage leaflets. .|Shaded....|June 20,’13| -4.5- 15 53.3 | 83.3 - 860
Red Rock Cab-
bage leaflets..|Not shaded|June 20,’13) -4.5 12 50.0 | 77.0 .955
Cabbage leaflets|Shaded....|June 25,’13) -3.5 36 52.8 | 77.7 .680
Cabbage leaflets|Not shaded|June 25,’13| -3.5 38 36.8 | 63.1 -875
Early Harvest
apple twigs
and leaves... ./Shaded..../June 28,’13) -4 39 0.0 | 35.9 | 1.975
Early Harvest
apple twigs
and leaves... .|Not shaded|June 28,13} -4 42 0.0] 6.8 | 2.438
Early Harvest
apple twigs
and leaves... .|Shaded....|June 28,’13) -5 47 34.0 | 70.0 | 1.975
Early Harvest
apple twigs
and leaves. ../Not shaded|June 28,’13] -5 50 0.0 | 48.5 | 2.438
Early Harvest
apple twigs
and leaves....|Shaded....|July 1,713) -4 34 0.0 | 19.8 | 1.930
Early Harvest
apple twigs
and leaves....|Not shaded|July 1,'13) -4 40 0.0 | 11.2 | 2.252
Early Harvest
apple. twigs
and leaves....|Shaded....|/July 1,’13) -5.5 38 0.0 | 40.1 | 1.930

 

 

 

 

 

 

 

 
 

 

 

 

 

 

 

 

 

 

Per-
Per- | cent-
Tem- | Number] cent- | age De-
Material Treatment; Date pera- of age | Total) pres-
ture | Plants | All | Leaf | sion
Killed] Area
Killed
Early Harvest
apple twigs
and leaves... .|Not shaded July 1,’13] -5.5 46 0.0 | 16.3 | 2.252
Pear twigs and |
leaves....... Shaded....'June 28,13) -4 25 24.0 | 74.0
Pear twigs and |
leaves....... Not shaded June 28,13] —4 28 0.0 | 36.6
Pear twigs and
leaves....... Shaded....|June 28,’13| -5 25 80.0 | 95.0
Pear twigs and
leaves....... Not shaded June 28,713) -5 26 15.4 | 63.4
Average, Shaded, excluding pears............s0eeceee 33.5 | 71.01) .985
Average, Not shaded, excluding pears.............. ---| 30.9 | 48.61] 1.173

 

In practically all cases the cortex, cambium and sap wood of the twigs were
injured rather severely, and in all cases the injury was worse with the
shaded twigs.

In the case of the pear twigs and leaves sufficient sap for depression determina-
tion could not be secured.

 

 

 

 

 

 

 

 

 

 

Per-
Per- | cent-
Tem- |Number| cent- | age | De-
Material Treatment} Date pera- oO age | Total | pres-
ture | Plants | All | Leaf | sion
Killed) Area
Killed
Labrusca grape |Shaded
leaves....... 38 hours .|July 8,’13] -3 18 27.2 {| 54.2 695
Labrusca grape
leaves....... Not shaded|July 8,'13) -3 17 35.3 | 58.8 | .733
Labrusca grape |Shaded
leaves........| 38 hours../July 8,’13] -4.5 22 100. 100. -695
Labrusca grape
leaves....... Not shadediJuly 8,'13) -4.5 17 76.4 | 94.1 133
Labrusca grape |Shaded
leaves....... 22 hours..|July 10,’13} -3.5 10 0.0| 2.5 | .755
Labrusca grape
leaves....... Not shaded|July 10,13) -3.5 10 0.0] 0.0 -920
Labrusca grape |Shaded
eaves....... 22 hours..|July 10,’13} -4.5 10 30.0 | 30.0] .755
Labrusca ‘grape
leaves....... Not shaded/July 10,’13) -4.5 10 0.0 | 15.0 920
Labrusca grape |Shaded
leaves....... 22 hours..|July 11,’13) -4 10 10.0 | 25.0 835
Labrusca grape |_ -
leaves....... Not shaded|July 11,’13] -4 10 0.0 | 17.5 | 1.085
Labrusca grape |Shaded
leaves....... 22 hours..|July 11,’13} -5.5 10 60.0 | 80.0 835
Labrusca grape
leaves....... Not shaded|July 11,'13} -5.5 10 40.0 | 52.5 | 1.085
Average; Shaded. oo ccisavcie suse ative ais:'s a1d0e anne side aussie dsua aie 34.53] 48.61) .761
Average, not shaded............. ccc cece ect ee eeenes 25.29] 39.65| .912

 
41

While the differences are not large, it will be seen that the sap
density of the shaded plants is uniformly lower and the killing
greater.

Ohlweiler! at the Missouri Botanical Garden seemed to find some
relation between the density of the sap of different plant species and
their resistance to cold. This is true especially in the case of the
different species of magnolia, where the leaf structure of species
with dense sap and of those with dilute sap is similar, so there
would not be this influence involved to modify the results.

From the beginning of these experiments, observations have
been made in autumn as to plants killed by the various early frosts
and freezing point determinations were made from leaves of these to
see if there is to be found any relation between hardiness and sap
density. In the following table the plants are listed as nearly as
could be determined according to hardiness, the most tender first,
though it is certain that almost any of the plants could be changed
two or three places in the succession and be as accurately placed in
order of hardiness. The depressions are also given. The leaves for
the depressions were all taken in the morning as soon as the dew was
off so they would be equally turgid.

TABLE 11. SHOWING THE RELATIVE HARDINESS OF GROWING PLANTS
CoMPARED WITH THEIR RELATIVE Sap DENSITY.

 

 

 

Plant Depression

Morning-Glory (Ipomoea purpurea)........6 0c cere cece eens .920
Coleus: (GC; Blwimes) is case avage diese Giere oe ssatccand ohh a Sees Gdn Dae d ove -428
Sweet Potato (Ipomoea Batatas)......... 0c ceeeee cece eceeeee 96

Moon Vine (Ipomoea Bona-Nox).......0eceeeeeeecccceeeee -863
Watermelon (Citrullus vulgaris).......... 00 cece cee ceeneeees . 882
Cantaloupe (Cucumis Melo).............0ce eee eee eee eee eens . 588
Cucumber (Cucumis sativus)........ 0.0 e es eeec cece ceeeeees .585
Caladium (Colocasia antiquorum) ............6eeeeeeeeeereee 745
Pumpkin (Cucurbita Pepo)...........scec cece neces eee eeees 785
Tomato (Lycopersicum esculentum)..........-.eeeeeee eee eeee - 832
Lantana (L. Camara)..........-s ccc cece scene seers ecereees -962
Dahlia (Dahlia variabilis)........... 0.2 cece cece erences 711
Blue Salvia (Salvia patens)......... cece eee eee eee e eee neees 1.025
Red Salvia (Salvia splendens)............0eeeecceerreeeeeecs . 765
Rose Geranium (Pelargonium graveolens)........... eee 1.835
Geranium (Pelargonium Hortorum)...........eeeeeeeee eens 1.075
Eggplant (Solanum Melongena)... .........--seeeeeeeeeneees .805
Alternanthera (Telanthera versicolor).......-+0+eeeeeeeeeeeee 1.058
Periwinkle (Vinca major)........ cece eee cece creer eee eeenee 1.20

Ageratum (A. comyzoides)..... 0. . cece eee c eee eee eeneeeees 1.055
Chard (Beta vulgaris var. Cycla)........... ee eee cee enneneene .805
Celery (Apium graveolens)..........0:c cece cece rece eeeeeeeee 1.442

123d. Anl. Rpt. Mo. Bot. Gard. 1912, pp. 101-31. (Bibl. 87).
 

 

Plant Depression
Gaillardia (G. pulchella).......... 00. cee eee ee teee eee eee ees - 803
Chrysanthemum (C. Sinense)...........-0 cece eee eee eeenee 1.955
Sedunt spectabiles iic4-c-daue no ne sew oie oR E EE EEA eka se SR Cees «575
Dandelion (Taraxacum officinale)............. 02 ee cee ee ee eens .975
Dock (Rumex crispus)........ cece ccc e eee c cect enee cnet eenes -997
Verbena. (Vii hy brida) 35 <sasfass. sme vores nas Heo Fas Ow Sew eR Se ES 1.093
Hollyhock (Althaea rosea).... 00... ccc cece ccc e cence aseee 1.130
Horse-radish (Cochlearia Armoracia)..............ecceceeeees 1.125
California Poppy (Eschscholzia Californica)..............0000. 1.198
Clover (Trifolium pratense)........ 0.00 cccec cece ceceecsseees 1.290
Violet (Viola odorata)......... cc cc ccc cece cece cece eeeeneees 1.225
Cabbage (Brassica oleracea)............ccececcecccvecceunees 1.115
Plantain (Plantago major)...........cc cc cece cceeeveeeeeoace 1.380
Strawberry (Fragaria Chiloensis)...............000ccceeseeees 1.865

 

 

All these depressions were determined as late in autumn as it
was possible to secure healthy tissue.

While it is evident that other factors than sap density influence
the hardiness, yet it seems true that more of the very tender plants
are found among those with slight depressions, and a majority of
the most hardy among those with greater density. It is possible
that if a larger list of plants were obtained, this might not be true.

All of these tests have been made with succulent plants that
kill at a temperature a few degrees below the freezing point. It is
true that some rather hardy plants like cabbage, kale, lettuce and
garden peas have been influenced in their killing temperature as great-
ly as have plants like tomatoes and cowpeas that kill at a tempera-
ture but slightly below the freezing point. However, in case of win-
ter wood, and buds that have developed great resistance to cold
by some sort of change, the problem would perhaps be different.
This experiment started with the idea that it might be possible to
increase the hardiness of buds of the peach in winter by increasing
the sap density through the use of fertilizers. Accordingly, plots
of peach trees at Dixon, Missouri, were fertilized with potassium
chloride at the rate of about 500 pounds to the acre, in the springs
of 1907, 1908, and 1909. Plots receiving potassium chloride at the
rate of a little more than 500 pounds to the acre during the seasons
of 1906, 1907, 1908, and 1909, were located in the orchard of the
Ozark Orchard Company at Goodman, Missouri; and plots receiving
480 pounds of potassium chloride to the acre, beginning March, 1910,
were located with the Ozark Fruit Farm Company, Brandsville
Missouri. Potassium was used in these experiments because some
experiments indicate that it is more readily taken into the cell to
become an osmotically active agent than most other mineral nutri-
43

ents. In these orchards we have had opportunity to observe the
results following cold periods that killed all the buds, cold periods
that killed nearly all of them, and cold periods that left a fair crop,
but in no case has there been any apparent effect on hardiness re-
sulting from the use of potassium as a fertilizer. Twigs were se-
cured from these plots in winter, spring, and summer and the density
of the sap of the cortex determined by expressing the sap, and deter-
mining its freezing point, and no difference in the density could be
detected between the plots fertilized with potassium and those re-
ceiving no fertilizer. These determinations could not be made with
sap from buds because it could not be secured in sufficient quantities.

If it were possible to increase the sap density by accumulation
in the cell of potassium or other materials applied to the soil, it could
possibly affect the killing temperature of the bloom or young fruits or
young growth in spring, even if it should have no effect on the killing
temperature of the buds in their dormant condition. C. Dussere?
observed apparently a slightly greater hardiness of young grape
shoots on vines that had been fertilized with potassium than on vines
that were not so fertilized. However, analyses failed to show the
presence of more potassium in the wood of those vines receiving
potassium fertilizer than in the wood of those that had not received
fertilizer.

It may be said that on our peach plots we have had occasion
to observe the effect of spring frosts on the bloom, as well as the
effect of winter cold on the buds and have failed to observe any dif-
ference due to application of potassium to the soil.

Briefly summerizing all our results with the relation of sap den-
sity to hardiness, we are safe in concluding that, at least in case of
plants not in a resting condition, a large amount of dissolved material
either in the sap within the cell or in a solution surrounding the cell,
will protect the cell from injury due to low temperature, to some ex-
tent at least. The protection where plants take the material into
the cell seems to be much less than where the material in solution
surrounds the cell, if the work of Maximow is confirmed.

The practical means of increasing hardiness seem to be very
limited. Withholding water from plants in a plant bed will check
the growth and thus increase the sap density and the hardiness. It
was thought possible that with such plants as cabbage which take up
potassium salts readily, watering in the plant bed with a solution
of such salts would tend to increase their hardiness. However, cab-
bage and tobacco plants growing in a hotbed soil watered for eighteen

1Bul. Soc. Sci. Nat. 5, ser 48 (1912) No. 176, pp. 393. (Bibl. No. 31).
44

days with a solution of potassium chloride ranging from 4.02 per
cent normal at first to 16.08 per cent normal toward the last showed
no increase in either sap density or hardiness over that of plants not
so treated. It is only in sand cultures that we have been ahle to
increase the sap density of plants by watering them with solutions.
If freezing to death results from too complete withdrawal of
water from the protoplasm, then, even with winter buds and wood, if
the sap density could be increased with some material that stays in
solution at temperatures lower than that at which the tissue kills,
it would hold more water in solution and thus lower the temperature
at which a killing degree of desiccation isreached. Miiller-Thurgau’s
measurements showed that a very large percentage of the water in
plant tissue is in the form of ice. In case of winter resting tissue
very little water can be left unfrozen at a killing temperature. If
freezing to death of plant tissue results from desiccation, then very
small quantities of water must be sufficient to protect the protoplasm
in case of the more hardy plants. Some writers hold that since some
plants continue to live after nearly all the water is frozen out, desic-
cation of the protoplasm can not be the explanation of death from
low temperatures. Others seem to hold the opinion that the pro-
tective action of the sap solute ends at the freezing point of the sap.
It should be remembered that so long as the temperature is above
the eutectic point of any of the sap solute, there will be some water pre-
sentin the liquid state. The number of degrees which the killing tem-
perature is lowered by an increase in sap density should be greater
with plants that kill at the lower temperatures. Thus in case of a
solution containing a gram molecule of a non-electrolyte in a liter of
water, the freezing point is -1.86° C. In case of a solution with
one-half of a gram molecule to a liter of water, the freezing point
would be -0.93° C. The following figures would evidently be approxi-
mately true:

 

Fraction of water un- | Fraction of water un-

 

Temperature frozen, gram-mole- frozen, one-half a
cule, in a liter of gram-molecule, in a
water liter of water

-0.93° C. all all
—1.86° C. all 1/2
-3.729 C, 1/2 1/4
-7.44° C, 1/4 1/8
-14.88°9 C, 1/8 1/16

-29.76° C. 1/16 1/32

 
45

This is, of course, assuming that the eutectic point of the solu-
tion is below these temperatures. It also assumes that the freezing
point is lowered exactly in proportion to the molar concentration
of the solution; that is, if there be four gram molecules in a liter of
water, the freezing point should be four times -1.86° C. This is
probably not quite true but the difference is so slight that it may be
ignored here. It will thus be seen that with a solution in which
there is a gram molecule to a liter of water of a solute that stays
in solution below -29.76° C., there would be as much water unfrozen
at -14.88° C., as there would be at -29.76° C., if the molar concentra-
tion is only half as great.

Maximow concludes that the protective action of the material
he used was greater than could be explained by the depression of the
freezing point of the sap. He may not have considered the above
facts. Another fact should be considered. With the plants Maxi-
mow used, possibly a large percentage of the sap solute crystallized
out at temperatures considerably above the minimum temperatures
that he used. Maximow used as a protective substance a solution
of equal density with the plant sap and with a low eutectic
point, then at a temperature of say -10° C., it would be considerably
more dense than the plant sap from which crystallization had taken
place. While theoretically the protective action of increased den-
sity should be greater with plants that kill at a rather low tempera-
ture like winter buds and wood, we have found no way to demonstrate
such protective action with such tissue. The only means of increas-
ing the sap density of such tissue that suggested itself to us was by
applying fertilizers like potassium chloride to the soil and this method
has not had that effect.

From the experience of Maximow and experience here with
cabbage and other plants where the salts in solution have increased
the resistance to cold as much as it was increased by organic com-
pounds, and in some cases more, it seems that one is safe in conclud-
ing that killing from cold is more likely a mechanical injury due to
the withdrawal of water from the protoplasmic membrane than an
injury resulting from the precipitation of proteids as suggested by
Gorke, since an increase in the percentage of any mineral salt should
tend to hasten the precipitation of proteids rather than reduce it.

It seemed that one good test of the theory of Gorke! would be
to find whether or not a lower temperature is required to precipitate
proteids from the sap of twigs as they increase in hardiness during

iLandw. Versuchs. Vol. 65, p. 149, 1906. (Bibl. No. 47).
46

early winter. It is known that from the time the leaves fall for at
least one or one and one-half months, the cortex as well as the winter
buds and the sap wood of deciduous trees (at least of peaches) con-
tinue to increase in hardiness. This Station made an effort to de-
termine whether this increase in hardiness might not be due to sucha
change in the composition of proteids that they would tend to remain
in solution at lower temperatures. Consequently twigs were gath-
ered on the dates shown in the following table, beginning before leaf
fall. Large quantities of cortex sap were expressed. After pouring
back and forth to insure a uniform solution, one-half of this sap was
frozen at the temperatures shown in the table, a temperature that
would at that time kill the cortex and practically all other tissue of
the twig. The other half was kept in an ice box until the freezing of

the other sap was complete, then both were taken to the Department ..

of Agricultural Chemistry for proteid analysis, the frozen sap being
thawed on the filter except when otherwise stated in the tables. The
analysis was by the following plan, kindly furnished by the Depart-
ment of Agricultural Chemistry:

KJELDAHL-GUMMING METHOD FOR ESTIMATION OF
NITROGEN.

“Weigh out accurately 4-6 grams of the sap by difference,
place in 500 c. c. Kjeldahl flask, add 0.7 gram of mercury and 25 c. c.
of sulphuric acid, heat for a few minutes until frothing ceases, add
7 grams of potassium sulphate and digest over a flame until clear,
cool; wash down the neck of the flask with distilled water, heat again
one hour until water is expelled. Cool and dilute with water until
flask is 2/3 full, add a piece of zinc and a piece of paraffin and 80c.c.
of alkaline solution containing 500 grams potassium sulphide and 18
kilos sodium hydroxide in 40 liters of thesolution. Distilinto standard
hydrochloric acid and titrate back with standard ammonium hydrox-
ide, using cochineal as indicator’. The factor 6.25 was used in re-
ducing nitrogen reading to proteid readings.

Twigs of apple, peach, pear and plum were used with results
as shown in the following table:
47

TABLE 12. SHOWING PERCENTAGE OF PROTEIDS IN FROZEN AND
UNFROZEN SAP FROM TISSUES OF APPLE, PEAR, PEACH AND PLuM.

 

 

  

; Tem- | Average per |Average per cent
Kind of Sap Date pera- | cent proteids. | proteids. Sap
ture Sap unfrozen frozen
Wealthy apple twigs...... Sept. 4,’11} -17 0.397 0.435
Wealthy apple twigs...... Oct. 2,’11}; - 9.5 0.556 0.544
Elberta peach twigs.......|Sept. 4,’11] -17 1.488 1.894
Elberta peach twigs...... Oct. 2,711) - 9.5 2.644 2.550
Elberta peach twigs......./Oct. 16,’11) - 9.5 2.550 2.531
Elberta peach roots....... Oct. 16,’11) - 9.5 1.563 1.563
Elberta peach twigs.......|Nov. 30,’11} - 9 2.050 2.100
Chabot plum twigs....... Sept. 4,’11] -17 0.651 0.694
Chabot plum twigs....... Oct. 2,'11] - 9.5 0.819 0.800
Kieffer pear twigs........ Sept. 4,’11} -17 0.144 0.031
Kieffer pear twigs........ Oct. 2,’11) - 9.5 0.406 0.375
Kieffer pear twigs........ Oct. 16,’11] - 9.5 0.288 0.288
Kieffer pear roots......... Oct. 16,711) -— 9.5 0.181 0.206
Kieffer pear twigs........./Nov. 30,’11| - 9 0.350 0.375

 

 

 

 

 

In no case does there seem to be any conclusive indications
that proteids were precipitated by temperatures low enough to kill
the plant tissue. Since there was no precipitation from the sap of
tender twigs in early autumn, sap was not taken from twigs later in
the season.

Cabbage and other succulent plants grown in the greenhouse,
some well watered, some under dry conditions and others grown out
of doors, also well watered but under conditions where they would
withstand lower temperatures than would those grown in the green-
house, had each an abundance of sap expressed, half of it being frozen
to a temperature that would kill those well watered in the greenhouse,
but would not kill those grown out of doors. Samples of each of
these frozen and unfrozen were analyzed for proteids, with the re-
sults shown in the following table:
48

TABLE 13. SHOWING PERCENTAGE OF PROTEIDS IN FROZEN AND
UNFROZEN SAP FrRoM SUCCULENT PLANTS.

 

 

 
 
  

Tem-| Average per | Average per
Kind of Sap Date pera- | cent proteids. | cent proteids.
ture Sap frozen. Sap unfrozen.
Cabbage greenhouse, dry

euies Peausemen atid Sasi Apr. 8,'12) -3 0.975 1.069
Cabbage, greenhouse...... Apr. 8,’12] -3 0.781 0.838
Cabbage, out-of-doors..... Apr. 8,’12] -3 1.406 1.438
Cabbage sap, outside..... Nov. 28,'11] -5 1.675 1.856
Cabbage, inside dry soil.. .|Oct. 28,11] -5 1.144 1.281
Cabbage, inside.......... Oct. 28,'11] -5 0.919 0.956
Tomato sap, greenhouse...|Dec. 1,'11] -3.7 0.594 0.438
Tomato sap, greenhouse,

Ory Soll is ies saesce tes Sie Dec. 1,'11] -3.7 1.313 1.444
Tomato sap, outside...... Dec. 1,'11] -3.7 0.700 0.713
Pea sap, inside...... .. Apr. 27,712] —-5 2.069 2.413
Pea sap, outside... Apr. 27,'12| -5 3.088 1.625
Lettuce, sap inside........|Apr. 27,'12| -5 0.519 0.613
Lettuce sap, outside...... Apr. 27,'12| -5 0.269 0.263
Kale, greenhouse......... Dec. 16,’11| -6.2 1.744 1.831
Kale, outside............ Dec. 16,'11) -6.2 1.963 1.994

 

 

 

 

 

In case of cabbage, kale, lettuce and peas there is some evidence
of precipitation in case of the more tender greenhouse plants, but
it is possible that the differences are within the range of experimental
error.

In March, 1913, apple roots that had been growing in the green-
house for sixty days had sap expressed, half of it frozen to a tempera-
ture that would kill them, the other half not frozen. At the same
time sap was taken from roots that had been kept in cold storage
at a temperature seldom varying from 32°F., with the following results:

TABLE 14. SHOWING PERCENTAGE OF PROTEIDS IN FROZEN AND
UNFROZEN SAP From APPLE Roots.

 

 

Percent-

Material Treatment Date age
Nitrogen

Apple stock, cold storage.......... Not frozen..| Mar. 14,13 0.325
Apple stock, cold storage.......... Frozen..... Mar. 14,'13 0.325
Apple stock, greenhouse........... Not frozen..| Mar. 14,'13 0.592
Apple stock, greenhouse........... Frozen..... Mar. 14,’13 0.548

 

 

 
49

In case of the greenhouse grown apple stock there seems to be
slight evidence that proteids were precipitated by the low tempera-
ture. However, the difference is probably within the range of error.
In these cases great care was taken to prevent any change in the
soluble proteid content of the sap before analysis began. The
unfrozen sap was immediately started for analysis, after being ex-
pressed. In all cases the frozen sap was thawed on filter paper so
that little change could take place after the thawing.

From the above tables, we are safe in concluding that in the
case of the cortex of twigs from fruit trees in autumn or early winter,
precipitation of proteids plays no part in the killing since tempera-
tures that will kill all the cortex will precipitate no proteids. In the
case of some succulent growing plants there seems some evidence
that a killing temperature will precipitate a slight percentage of the
soluble proteids present, but since increasing the amount of salts
present that are supposed to precipitate the proteids increases in-
stead of decreasing the resistance to low temperature, we are probably
safe in concluding that precipitation of proteids does not explain
freezing to death.

OTHER FEATURES THAT INFLUENCE THE FREEZING TO
DEATH OF PLANTS.

Rate of Thawing. The effect of the rate of thawing on the
killing from cold has been discussed previously with reference to
the works of Miiller-Thurgau,! Molisch,?, and Sachs.? However,
it is not out of place to discuss it briefly as one influence to be dealt
with in the killing of certain plants from cold. As mentioned before,
Miiller-Thurgau and Molisch found only mature fruits and leaves
of Agava Americana to be affected by the rate of thawing. Prac-
tically all plants used in freezing experiments to be reported in this
paper have been tested with reference to the effect of rapid thawing,
particularly because of the effect such thawing would have on the
results with other experiments. The following table gives the re-
sults with peach fruit buds that were thawed slowly and rapidly:

‘Landw. Jahrb. Vol. 15, p. 453, 1886. (Bibl. No. 78).

2Untersuchung tiber das Erfrieren, etc. Book, 1897. (Bibl. No. 75).

‘Ber. u. d. Ver. d. Kon. Sachs. Gesell. d. Wiss. zu. Leipzig, 1860, Vol. 12, pp. 1-50. (Bibl.
No. 94),
50

TABLE 15. SHOWING THE EFFECT OF SLOW AND RAPID THAWING
ON THE AMOUNT OF KILLING oF PEACH FRUIT Bubs.

 

 

 

 

 

 

 

Tem- | Number |Percent-
Variety Treatment Date pera- oO! age

ture Buds Killed
Hills Chili........... Thawed rapidly..|Jan. 21,’11] -—21 178 40
Hills Chili........... Thawed slowly.. is 21,'11| -21 200 51.1
Hills Chili........... Thawed rapidly..\Jan. 22,'11] —20.5] 100 7.0
Hills Chili........... Thawed slowly..|Jan. 22,'11) -20.5/ 100 23.0
LO WIS oe ieecensctareeceie Thawed rapidly..|Feb. 9,’11] -20.2) 100 7.0
LO WIS o.:csseiessiess: F500: Thawed slowly..|/Feb. 9,’11] -20.2) 100 20.0
Elberta............. Thawed rapidly..|Dec. 8,’11/ -16 110 20.9
Elberta............. Thawed slowly..|/Dec. 8,’11] -16 100 8.0
Elberta............. Thawed rapidly..)Dec. 13,’11] -16 75 94.6
Elbertaiiise% anes oes Thawed slowly../Dec. 13,11] -16 80 100.0
Rice’s Seedling. ..... Thawed rapidly..|Mar. 24,’13| ~16 129 72.2
Rice’s Seedling...... Thawed slowly..|Mar. 24,'13] -16 130 84
Elberta ...i66tse%e. Thawed rapidly..|Mar. 24,’13] -16 95 95.8
Elberta............. Thawed slowly..|Mar. 24,'13) -16 83 90.4
Average, Thawed rapidly........... ccc cece cece nce eveceeececs 38.93
Average, Thawed slowl Wisse 2s 0 ax 0 ave $ ae-a.nie 8 6/006 6.05825 Gob 6 sue arate eae eo 53.61

 

 

The buds were thawed slowly by simply lifting the inner cyl-
inder to which they were attached and seeing that the temperature
was raised to four or five degrees above that to which they were low-

ered.

In no case was it possible that the temperature could have

gone back to the minimum temperature recorded, and usually twelve

hours, sometimes slightly more, were required for the thawing.
Enough buds were frozen to justify a positive conclusion that

rapid thawing does not influence the amount of killing.
The following table gives the results of slow and rapid thawing

of young fruits:
5I

TABLE 16. SHOWING THE EFFECT OF THE RATE OF THAWING ON
FREEZING TO DEATH OF YOUNG FRUIT.

 

 

 

 

 

 

 

Age of Manner Tem- | Number |Percent-
Kind of Fruit | Fruit Date oO pera- of age
in days Thawing ture | Fruits | Killed
Lewis peach...... 30 |May 17,'13| Rapidly in
room..... —4 23 43.5
Lewis peach...... 30 |May 17,'13| Slowly in
freezer 4 24 25.0
Early Bernard.... Rapidly in
peach.......... 35° |May 21,13 room..... -4 34 61.8
oe Bernard Slowly in ;
eer 35 |May 21,'13 freezer. -4 34 91.2
Biberta Seedling Rapidly in
Aa iesdaeh Suse 38 |May 24,'13 room.....| —4 21 61.9
ptberta Seedling Slowly in
Senooeens ease 38 |May 24,'13 room.....| —4 30 30.0
eben Seedling Rapidly,
peach.......... 38 |May 24,713 fanned —4 25 44.0
cares Peer 3 Rapidly in
dia. 1 44 |May 31,’13 room..... -4 20 40.0
Carman peach” Rapidly in
dia. lin........ 44 |May 31,713 sun...... —4 20 45.0
Carman peach Rapidly,
dia. lin........ 44 |May 31,13) | fanned 4 20 45.0
Carman peach Slowly in
dia. lin........] 44 |May 31,’13|} — freezer 4 20 45.0
Waddell peach Rapidly in
dia. 14 in......| 52 |June 6,'13 room..... 4.5 22 81.9
Waddell peach Slowly in
dia. 14in......] 52 jJune 6,13) freezer 4.5) 22 70.0
Waddell peach Rapidly,
dia. 14g in......}| 52 |June 6,13 fanned....]| 4.5 22 80.0
Seedling peach....| .. |June 11’,13] Rapidly in
room..... 4.5 15 46.7
Seedling peach... . June 11,13] Slowly in
freezer....]| -4.5 16 25.0
Jonathan apple....| 23 |May 17,’13) Rapidly in
room..... —4 19 68.4
Jonathan apple....| 23 |May 17,'13| Slowly in
freezer....| —4 15 60.0
Jonathan apple....| 30 |May 24,’13) Rapidly in
room..... —4 23 56.5
Jonathan apple....| 30 {May 24,’13) Slowly in
] ‘ : ee beer -4 31 80.7
onathan apple....) 30 |May 24,’13) Rapidly,
aa rs . tah te fanned -4 19 78.9
alome apple...... une 11,’13) Rapidly in
er ) thors eee -4 15 46.7
Salome apple...... June 11,'13} Slowly in
man ‘ wae ieee | 4 15 33.3
yehouse cherry.. May 17,’13| Rapidly in
26 i ou, weee| 4 15 66.7
Dyehouse cherry.. May 17,13) Slowly in
freezer....| —4 18 16.6
Dyehouse cherry. . May 21,13) Rapidly in
room..... 4 38 39.5
Dyehouse cherry.. May 21,'13| Slowly in
freezer 4 47 80.9
Average, Rapidly in room..... 20.2... se eee cnet eee eee eees 55.8
Average, Slowly in freezer... 2... 0... e eect tenet eee eenes 50.7

 

 
52

The fruits were thawed slowly by removing some of the salt
and ice from the freezer and if necessary lifting the lid to the freezer
so the temperature inside would immediately cool to about one
degree centigrade above that to which the fruits were run. This was
done in order to be certain that the slowly thawing fruits did not
suffer greater killing by being kept at the minimum temperature
longer than the rapidly thawed fruits. Approximately three hours
were required for succulent plants and fruits to thaw in this way. It
is apparently certain that the rate of thawing has little to do with the
amount of killing of young peaches and apples. Not enough cher-
ries were tried to justify conclusions.

It will be seen in the table that some of the fruits were fanned
in thawing. These fruits were taken in the frozen condition from
the freezer and put at once in the current from an electric fan to see
if rapid evaporation during thawing and shortly afterward influences
the killing. The results indicate that it does not.

Results at this station from freezing ripe winter apples agree
with those of Miiller-Thurgau and Molisch that unless the tempera-
ture goes too low, slow thawing will greatly reduce the amount of
killing. With the very young fruits, however, there is no indication
that the rate of thawing influences the killing.

The following table gives the results of freezing apples in early
July that ripen in September; pears that ripen in August and Septem-
ber, ripe Yellow Swan peaches and Elberta peaches that ripen about
August 15th in Columbia, and Krummel October peaches which
ripen in September in Columbia:
53

TaBLE 16. SHOWING RELATIVE EFFECTS OF SLOW AND RapIpD
THAWING OF FROZEN GREEN FRUIT OF APPLE, PEAR, PEACH

 

 

 

 

 

 

 

AND PLUM.
Percent-
Tem- | Number | age of
Material Date pera- of Fruits Remarks
ture | Fruits | Showing
Injury
Jonathan apples, 114
in. in diameter Seeds
(Thawed rapidly)....|July 11,’13) -5 10 80 uninjured
Jonathan apples, 1144
in. in diameter Seeds
] (lnewed slowly! shes July 11,713} -5 10 100 uninjured
onathan apples
half grown 5 .
j (Thawed rapidly) -++-(July 14,13} -5 6 100 Slight injury
onathan apples,
half grown
] aad Bowl Sissies July 14,’13} —-5 6 100 Slight injury
onathan apples, ond
] ieee rapidly)....|July 17,’13) -5 5 100 Slight injury
onathan apples, eA
nee meme Bede July 17,’13} -5 5 100 Slight injury
enheim apples
ripe apis
aie ca sarily) ....{July 14,713) -5 4 100 Slight injury
enheim apples,
ripe : fain 8
5 awe eee nies July 14,713) -5 4 100 euent injury,
uchess pear, eeds of in-
in. in diameter jured fruit
(Thawed rapidly)..../July 11,'13| -5 10 70 dead
Duchess pear, 14% Seeds of in-
in. in diameter.... jured fruit
2 (Thawed slowly) ..../July 11,'13) -5 10 60 dead
yson pear,
half-grown ae
. (Thawed rapidly)..../July 14,713} -5 4 100 Slight injury
'yson pear,
half-grown ' oes
ib pared slowly).....|July 14,’13) —-5 4 100 Slight injury
uchess pear
green , ser tes* obs
D (Thawed rapidly)....|/July 17,713) —-5 5 100 Slight injury
uchess pear, green Aes
(Thawed slowly)..... July 17,'13) -5 5 100 Slight injury
Keommel October verde ot ea
peac jured frui
Thawed rapidly)..../July 12,713) -5 10 100 killed
Cue Pe Flesh | thawed
each in freezer lit-
Thawed slowly)..... July 12,’13} -5 10 100 tle less injured
54

 

 

 

 

 

 

 

 

Percent-
Tem- | Number | age of
Material Date pera- of Fruits Remarks
ture | Fruits |Showing
Injury
Elberta peach, green : 2
(Thawed rapidly)....|July 14,’13) —-5 5 100 Slight injury
Elberta peach, green panke
(Thawed slowly)..... July 14,713} -5 5 100 Slight injury
Yellow Swan peach,
ripe
(Thawed rapidly)....|July 14,’13) -5 4 100 Slight injury
Yellow Swan peach,
ripe = ‘ ae
(Thawed slowly)..... July 14,713) —-5 4 100 Slight injury
Elberta peach,
green : ;
(Thawed rapidly)....|July 17,’13} —-5 5 100 Injury slight
Elberta peach,
green
(Thawed slowly)..... July 17,713} -5 5 100 Injury slight
Graves peach, ripe :
(Thawed rapidly)..../July 17,'13| —-5 5 100 Injury slight
Graves peach, ripe .
(Thawed slowly) ...|July 17,’13} -5 5 100 Injury slight
Wild Goose plum,
green Injury rather
(Thawed rapidly)....|July 14,'13| -5 5 80 severe
Wild Goose plum,
green Injury rather
(Thawed slowly)..... July 14,713) -5 5 100 -} severe
Wild Goose plum,
ripe Injury rather
(Thawed rapidly). .../July 14,713) —-5 5 100 severe
Wild Goose plum,
ripe Injury rather
(Thawed slowly) July 14,’131 -5 5 100 severe
Average, green fruits rapidly thawed............... 93.6
Average, green fruits slowly thawed............... 96.4

 

Those fruits that were thawed slowly were thawed in the same
manner as the young fruits in the previous table. They were thawed
as slowly as it was possible to thaw them. Ice without salt was
packed over the freezer and left over night. For those frozen July
14th, the temperature at 5:05 P. M. was -4.5° C; at 5:30 P. M., -3.5°
C; at 5:45 P. M., -3° C, and at 6:30 A. M. the next day it was 9.5° C.
The temperature rise for the other freezings was approximately the
same. The ice was all out of the fruits thawed rapidly in a warm
55

room in a few minutes. In no case was there any evidence that the
rate of thawing affected the amount of injury to the unripe fruit,
or even to the partially ripe Yellow Swan peaches. It seems proba-
ble that slow thawing affects the amount of injury to fruits only in
case of ripe apples and pears.

The following table gives the results of slow and rapid thawing
of some garden plants:

TABLE. 17. SHOWING THE EFFECT OF SLOW AND RAPID THAWING

ON LEAVES AND STEMS OF GROWING PLANTs.

 

 

 

 

 

 

 

 

 

Per-
Per- | cent-
F Manner Tem- | Num-| cent- | age
Material ° Date pera- | ber of | age | Total
Thawing ture |Leaves| all | Sur-
Killed] face
Killed
Cowpeas Rapidly in room.|May 28,'13) -3.8 | 12 25
Cowpeas Slowly in freezer |May 28,'13| -3.8 26 100
Cowpeas.. Rapidly in sun. .|May 28,'13| -3.8 25 100
Cowpeas.. Rapidly in room./June 14,’13) -4 3 100 100
Cowpeas.. Slowly in freezer./June 14,’13} —4 3 is 90
Lettuce... Rapidly in room.|May 7,13} -4 27 | 22.2 | 37
Lettuce.......... Slowly in freezer.|;May 7,’13] -—4 20 5.0 13
Lettuce.......... Rapidly in room./May 13,’13) -4 4 ies 90
Lettuce.......... Slowly in freezer.|May 13,’13| -4 3 ae 50
Lettuce (Black

Seeded Simpson)| Rapidly in room.|June 12,13] -4 9 | 66.6] 92
Lettuce (Black

Seeded Simpson)| Slowly in freezer.jJune 12,13) -4 11 36.6 50
Lettuce (Black

Seeded Simpson)| Rapidly in room.|June 12,’13| -4 10 | 90.0 | 97.5
Lettuce (Black

Seeded Simpson)! Slowly in freezer./June 12,13] -4 10 | 90.0 | 97.5
Kale waxes nus ts Rapidly in room./May 15,’13| -5 6 16.6 | 20.8
Kale sisasicvswes ax Slowly in freezer.|May 15,'13| -5 5 0.0} 0.0
Kale... scciouses es Rapidly in room.|June 28,’13| -3.5 5 |100.0 {100.0
Kale g csiecases s0cqeis oe Slowly in freezer.|June 28,’13) -3.5 5 {100.0 |100.0
KG 5. 5 Scicae ates cece Rapidly, fanned .|June 28,’13] -3.5 5 {100.0 |100.0
Kal sj siscsce.c-nc-e ae Rapidly in room.|July 3,’13) -3.5 5 | 80.0 | 95.0
Kale occicciees ceareee Slowly in freezer.|July 3,’13} -3.5 5 80.0 | 95.0
Cabbage.......... Rapidly in room./May 15,'13| -5 4 |100.0 |100.0
Cabbage.......... Slowly in freezer.|May 15,’13) —5 4 |100.0 |100.0
Red Cabbage..... Rapidly in room.|May 15,'13) -5 5 | 20.0 | 20.0
Bed Cabbage aaa ise Slowly in freezer |May 15,’13] -5 9 | 33.3 | 33.3

abbage,
is Flat Dutch ers Rapidly in room.|June 12,13) -4 20 {100.0 |100.0

abbage,

Flat Dutch deciees Slowly in room. .|June 12,’13| -4 10 |100.0 |100.0
Cabbage.......... Rapidly in room.|June 28,'13| -3.5 5 | 40.0 | 85.0
Cabbage.......... Slowly in freezer.|June 28,’13] —3.5 5 | 40.0 | 85.0
Cabbage.......... Rapidly, fanned .|June 28,13) -3.5 5 | 40.0 | 85.0
56

 

 

 

 

 

 

 

 

Per-

Per- | cent-

Manner Tem- | Num-| cent- | age

Material of Date pera- | ber of | age | Total
Thawing ture |Leaves| ail Sur-

Killed| face
Killed

Cabbage,

Red Rock...... Rapidly in room.|June 30,13] —4 5 | 40.0 | 65.0
Cabbage,

Red Rock...... Slowly in freezer.|June 30,’13| -4 5. | 60.0 | 65.0
Cabbage, :

Red Rock...... Rapidly, fanned.|June 30,13] —4 5 | 60.0 | 70.0
Tomatoes......... Rapidly in room.|June 28,13) -3.5 26 {100.0 |100.0
Tomatoes......... Slowly in freezer.|June 28,’13) -3.5 25 |100.0 |100.0
Tomatoes......... Rapidly, fanned.}June 28,13) -3.5 25 {100.0 |100.0
Elberta

peach leaves....| Rapidly........ July 16,'13] -6 9 | 44.4 | 58.9
Elberta

peach leaves....| Slowly.......... July 16,13) -6 8 0.0 | 25.0
Elberta

peach leaves....| Rapidly........ July 17,'13) -5 57 0.0 | 17.9
Elberta

peach leaves....| Slowly.......... July 17,’13) -5 58 0.0 | 18.9
Late Duchess *

apple leaves.....| Rapidly........ July 16,'13) -6 22 0.0 | 28.4
Late Duchess ‘

apple leaves.....| Slowly.......... July 16,713) -6 19 0.0 | 19.7
Late Duchess

apple leaves.....| Rapidly........ July 17,'13| -5 51 0.0 | 27.4
Late Duchess

apple leaves.....| Slowly .......... July 17,'13) -5 55 0.0 | 26.3
Average, Leaves of succulent plants, thawed slowly...............0005 68.4
Average, Leaves of succulent plants, thawed rapidly.................- 76.3
Average, Same, excluding lettuce, thawed slowly................e00005 74.4
Average, Same, excluding lettuce, thawed rapidly.............c0eeee00 76.2

 

 

In none of these plants, except lettuce, does there seem to be
any difference in the amount of killing om account of the rate of thaw-
ing. Lettuce, however, seems to have the amount of injury reduced
by slow thawing. Even with lettuce, however, a slight reduction
in temperature, certainly not more than one degree, would offset the
effect of slow thawing.

Effect of Wilted Condition on Killing Temperature. The condi-
tion of plant tissue at the time of freezing with reference to turgidity
seems to have something to do with the killing. In all freezings
care has been taken to have all of the plants kept in an equally turgid
condition, or as nearly so as it was possible to maintain, though to
find to what extent slight difference in turgidity might alter results,
a considerable number of plants were frozen, some turgid and some
wilted. The following table gives a list of freezings and the results:
57

TaBLe 18. SHowiING EFFreEct oF WILTING OF PLANT TISSUE ON
Its RESISTANCE TO CoLp (FRuItTs).

 

 

 

 

 

 

 

 

Per-
: Tem- | Number |Percent-| cent-
Material Date pera- of age age
ture | Fruits } Killed | Weight
Lost
PEACHES
Elberta Seedling, turgid....... May 24,’13} -4 21 61.9
Elberta Seedling, wilted on
CWE we cniienws vames wa ede ease May 24,’13| +4 29 17.2
Elberta Seedling, wilted 314
hrs. detached.............. May 24,'13| -4 29 24.2 27.6
Lewis, fresh................. May 19,13} -4 23 43.5
Lewis, wilted 6 hrs. on twig...|May 19,'13) —4 22 45.5
Early Bernard, turgid........ May 21,’13} -4 34 61.8
Early Bernard, wilted 5 hrs.
ON tWIg.... eee eee ee eee May 21,’13) -4 53 69.8 4.0
APPLES
Jonathan, turgid............. May 24,’13| -4 23 56.5
Jonathan, wilted on twig...... May 24,’13| -4 29 83.8 2.0
Jonathan, wilted detached..../May 24,’13| -4 26 65.4
Jonathan, turgid............. May 19,’13] -4 19 68.4
Jonathan,$wilted on twig 6 hrs.|May 19,’13| -4 37 86.5
Salome, turgid............... June 12,’13) -4.5 15 46.7
Salome, wilted on twig........ June 12,’13) -4.5 12 50.0
CHERRIES‘
Dyehouse, turgid............ May 21,'13| -4 38 39.5
Dyehouse, wilted 5 hrs. on
EWG scicicpcsscenasancee elasnesay a wid, Seay May 21,’13} -4 56 21.4 3.4
Average percentage of fruits killed, fresh....... pete gale 54.0
Average percentage of fruits killed, wilted on twig......... 53.5

 
58

TABLE 18a. SHOWING EFFECT OF WILTING OF PLANT TISSUE ON
Its RESISTANCE TO COLD. (SUCCULENT PLANTS.)

 

 

 

 

 

Percent-| Per-
Tem- | Num-|Percent-| age cent-
Material Date pera- | ber of | age all | Total age
ture /Leaves| Killed | Surface | Weight .
Killed Lost
Tomato, turgid........ Aug. 10,’12] -3 2 80.0
Tomato, wet and turgid|Aug. 10,’12| -—3 2 90.0
Tomato, wilted........ Aug. 10,'12| -3 2 85.0
Tomato, turgid........ Aug 11,’12| -2 2 20.0
Tomato, wet and turgid|Aug. 11,'12] -2 2 40.0
Tomato, wilted........ Aug. 11,12} -2 2 30
Tomato, turgid........ June 25,’13) -2.5 32 50.0 72.6
Tomato, wet and turgid|June 25,’13| -2.5 32 69.2 88.4
Tomato, wilted........ June 25,’13| -2.5 | 37 43.2 62.8 15.6
Tomato, turgid........ June 30,713) -2.5 | 35 eeibe 97.5
Tomato, wilted........ June 30,'13} -2.5 24 sees 58.0 28.0
Kale, turgid.......... July 3,13) -3.5 5 80.0 95.0
ee eens: July 3,713) -3.5 5 60.0 85.0 35.4
ed Rock Cabbage,
turgid.............. June 30,'13} -4 5 65.0
Red Rock Cabbage,
wilted secncn sacs see June 30,'13} —4 4 43.9 16.8
Lima bean, turgid..... June 22,’12| -2 5 15.0
Lima bean, wilted..... June 22,'12| -2 5 75.0
Lettuce, turgid........ July 25,'12| -2 5 0.0
Lettuce, wet and turgid|July 25,12] -2 5 50.0
Lettuce, wilted......../July 25,'12/ -2 5 0.0
Lettuce, turgid........ July 27,12} -2 5 0.0
Lettuce, wet and turgid/July 27,'12] -2 5 30.0
Lettuce, wilted........ July 27,’12| -2 5 60.0
Lettuce, turgid........ July 30,’12| -2 5 25.0
Lettuce, wet and turgid|July 30,’12] —2 5 25.0
Lettuce, wilted........ July 30,’12| -2 5 35.0
Black Seeded Simpson
lettuce, turgid....... June 12,’13) -4 9 92.5 66.6
Black Seeded Simpson
lettuce, wilted....... June 12,'13| -4 9 33.3 55.5 23.4
Black Seeded Simpson
lettuce, turgid....... June 13,713) -4.5 12 75.0 83.0
Black Seeded Simpson
lettuce, wilted....... June 13,'13) -4.5 14 57.0 62.0 21.8
Turnip, turgid........ July 25,’12| -2 4 0.0
Turnip, wet and turgid |July 25,’12] -2 4 30.0
Turnip, wilted........ July 25,’12} -2 4 30.0
Turnip, turgid........ July 27,’12] -2 4 40.0
Turnip, wet and turgid |July 27,712] -2 4 10.0
Turnip, wilted........ July 27,’12| -2 4 10.0
Red Clover, turgid...../July 22,'12/ -2 4 17.0
Red Clover, wilted...../July 22,’12) -2 4 34.0
Red Clover, turgid...../July 24,’12) -3 4 100.0
Red Clover, wilted.....|July 24,712! -3 4 66.0
Rose Geranium, turgid.|July 22,12) -2 4 97.0
Rose Geranium, wilted./July 22,’12! -2 4 60.0
Rose Geranium, turgid.|July 24,712} -3 4 100.0

 

 

 

 
59

 

 

 

 

 

 

 

Percent-| Per-
. Tem- |Num-|Percent-| age cent-
Material Date pera- | ber of | age all | Total age
ture |Leaves| Killed | Surface | Weight
Killed Lost
Rose Geranium, wet
and turgid.......... July 24,12] -3 4 100.0
Rose Geranium, wilted.|July 24,’12| -3 4 100.0
Common Geranium,
turgid............65 July 24,'12| -3 “4 95.0
Common Geranium,
wet and turgid...... ‘July 24,712) -3 4 90.0
Common Geranium,
wilted..........6565 July 24,’12| -3 4 100.0
Common Geranium,
turgid............+. July 31,’12] -2 4 100.0
Common Geranium,
wet and turgid...... July 31,'12] -2 4 80.0
Common Geranium,
wilted.........e0005 July 31,'12) -2 4 100.0
Morning-glory, turgid..|July 31,’12; —2 3 100.0
Morning-glory, wet
and turgid.......... July 31,’12| -2 3 100.0
Morning-glory, wilted..|July 31,’12) —2 3 0.0
Morning-glory, turgid..;Aug. 3,'12| -2 4 15.0
Morning-glory, wet
and turgid.......... Aug. 3,712] -2 4 100.0
Morning-glory, wilted..|Aug. 3,’12] —2 4 15.0
Coleus, turgid......... Sept. 3,712] -2.5 4 25.0
Coleus, wet and turgid |Sept. 3,’12} -2.5 4 50.0
Coleus, wilted......... Sept. 3,712} -2.5 4 100.0
Fern, turgid.......... Sept. 6,’12| -2 5 0.0
Fern, wet and turgid...|Sept. 6,712) —2 5 15.0
Fern, wilted.......... Sept. 6,'12| -2 5 60.0
Fern, turgid.......... Sept. 7,’12] -2 5 5.0
Fern, wet and turgid...|Sept. 7,’12| -2 5 7.0
Fern, wilted.......... Sept. 7,712] -2 5 20.0
Fern, turgid.......... Sept. 9,712} -2 5 40.0
Fern, wet and turgid.../Sept. 9,’12| —2 5 55.0
Fern, wilted.......... Sept. 9,’12) -2 5 40.0
Mulberry, turgid...... Sept. 9,12} -2 5 5.0
Mulberry, wet and
CUPS soa ciinsiscaue oa ed Sept. 9,’12| -2 5 0.0
Mulberry, wilted...... Sept. 9,'12] -2 5 0.0
Average percentage surface killed, leaves of succulent
plants, turgid....... 06... cece eee eee eee teen ee 50.3
Average percentage surface killed, leaves of succulent
plants, wilted........ cc cece eee eee eee eee eeeeees $1.4

 

 

 

On January 22, 1913, apple roots from one-year-old seedling
stock were frozen to -9° C in 314 hours:
(a) Two kept in water 18 hours.

All were injured. The crown cuts slightly in cambium;
and the second and third in cambium and cortex severely.
60

(b) Two roots kept in saw dust.

The crown cuts were very slightly injured; the second and
third were more severely than the crown cuts, but less severely
than the second and third cuts of (a).

(c) Two dried roots—allowed to dry on desk eighteen hours.

Crown cuts and second cuts entirely uninjured. Very
slight injury in cambium region of third cut.

There is some indication that rapid wilting in case of some
plants reduces the injury from freezing. However, in the case of
most plants the difference is rather slight and with many plants
there is no apparent difference. In all cases the wilting was suf-
ficient to give the tissue a limp appearance. It seems rather certain
then that wilting so slight that it can not be easily detected by the
appearance or feel of the tissue could not influence the results in freez-
ing such tissue as our plants with roots or stem bases in solutions.
In case of plants with the surface wet, listed in the table as wet and
turgid, there seems strong evidence that the killing from freezing is
worse.

Long continued partial withholding of water is different. The
rate of growth, sap density and possibly the resistance of the pro-
toplasm to the results of low temperature are increased. There
is no apparent reason to expect this of rapid wilting. It would tem-
porarily increase the sap density by reducing the amount of water
in the cell. It probably does not, however, increase the amount
‘of material in the cell to hold water. Plants growing with insuf-
ficient water supply are generally more resistant to cold (See tables
IV, V, and VI). We have also some results of this effect of con-
tinued partial withholding of water on dormant peach buds. On
November 20, 1910, typical branches of peach trees were girdled, a
ring being cut nearly through the sap wood, and another limb was cut
off and set up in the tree. This was done with several trees. The
following table gives the percentage of buds killed when the tempera-
ture went to -8° F., on January 3, 1911:
61

TaBLe 19. SHOWING EFFECT OF SLOW DRYING OUT ON HARDINESS
oF PEAacH BupDs IN WINTER. é

 

 

 

 

 

 

Number |Percent-
Variety Buds From Date o age

Buds Killed
Barnes...... Girdled branch................ Jan. 14,’11 321 19.3
Barnes...... Cut off branch................. Jan. 14,’11 275 29.5
Barnes...... Check, normal branch.......... Jan, 14,’11 325 86.0
Connolly....}| Girdled branch................ Jan. 14,’11 198 68.7
Connolly....| Cut off branch................. Jan. 14,’11 281 68.0
Connolly....| Check, normal branch.......... Jan. 14,11 217 89.9
Hills Chili...| Girdled branch................ Jan. 14,711 501 11.4
Hills Chili...| Cut off branch................. Jan. 14,’11 351 18.0
Hills Chili...] Check, normal branch.......... Jan. 14,’11 465 45.2
Average, Girdled branch. ........ 0... cece cece cece cece ener eeeee 33.1
Average, Cut off branch ....... 0... cece ecw e reece eceee ene enttane 38.5
Average, Check, normal branch........... 0c ccc e cece eee e teense 73.7

 

 

It is plain that this slow loss of water in case of winter resting
fruit buds has increased the resistance of the tissue to low tempera-
ture.

Rate of Freezing. Pfeffer! makes the following statement with
reference to the rate of freezing: ‘‘Resistant plants withstand
rapid and slow cooling equally well, and it is doubtful whether a rapid
fall of temperature is more injurious to plants killed by freezing
than is gradual cooling. That the injury is not due to the sudden
formation of ice after sub-cooling is shown by the fact that a peeled
potato is killed by freezing, although no sub-cooling occurs and the
ice forms gradually at -1° C., the freezing point of the sap.” How-
ever, lately Winkler?, working with Pfeffer, finds that with winter
twigs that on cooling rapidly to -22° C. will be killed, if they are kept
for three days at -16° C., two days at -18° C., three days at -20° C.,
two days at -22° C., three days at -25° C., and twelve hours at -30°
to -32° C., they were not all killed.

The rate of temperature fall is very important indeed, especially
in case of winter buds. In fact apple buds can be frozen in a cham-
ber surrounded by salt and ice rapidly enough that practically all
of them will be killed at a temperature of zero F., or slightly below,
while it is well known that they may go through a temperature of

1Phys. of Plants. Eng. Trans. by Ewart, Vol. 2, p. 235. (Bibl. No. 88).
Jahrb. f. Wiss. Bot. Vol. 52, 1913, pp. 467-506. (Bibl. No. 121).
62

20° F. to 30° F. below zero with but slight injury where the tempera-
ture fall is not so rapid. No fruit buds have been found on the
Experiment Station grounds that can not be killed by a temperature
secured by salt and ice when in the most dormant state, by very rapid

fall.
the results:

The following is a list of the freezings in our laboratory, with

TABLE 20. SHOWING EFFECT OF SLOW AND RAPID TEMPERATURE
FALL ON FREEZING TO DEATH OF PLANT TISSUE.

 

 

 

 

 

 

 

 

 

 

 

 

 

Num- |Percent-| Num- |Percent-
Kind of Buds Date ber age ber age
Buds Killed Buds Killed
Slowly to -19.59 C. /Rapidlyto-17.7° C,
Rice’s Seedling peach....... Jan. 25,713 80 15 55 96.4
Yellow Swan peach......... Jan. 25,713 64 28 86 100.0
Early Richmond cherry.....|Jan. 25,'13] 100 16 90 97.7
Slowly to -20° C. |Rapidly to -19° C.
Rice’s Seedling peach....... Feb. 15,'13; 117 10.3 68 100.0
Yellow Swan peach......... Feb. 15,13 95 30.5 64 100.0
Early Richmond cherry..... Feb. 15,’13} 100 45.0 89 98.8
Dyehouse cherry........... Feb. 15,'13 83 22.9 90 97.6
Slowly to -18.59 C. [Rapidly to -129 C.
Rice’s Seedling peach....... Mar. 15,13] 104 42.3 101 37.6
Elberta peach............. Mar. 15,713) 104 97.7 86 61.6
Jonathan apple............ Mar, 15,13 35 34.3 20 70.0
Montmorency cherry....... Mar. 15,'13 85 14.1 87 17.2
Lombard plum............ Mar. 15,’13) 112 12.9 99 47.3
Slowly to -15.5° C. |Rapidly to -10° C.
Hills Chili peach........... 63 17.3 49 10.2
Rice’s Seedling peach....... 104 10.6 81 4.9
Early Richmond cherry..... 94 29.8 73 54.8
Slowly to -189 C. |Rapidlyto-13.59C.
Elberta peach............. Mar. 8,'13/ 66 30.3 92 70.6
Hills Chili peach........... Mar. 8,'13) 120 20.8 71 76.0
Rice’s Seedling peach.......|Mar. 8,'13 70 21.4 82 54.9
Slowly to -18° C. |Rapidlyto-13.5°C.
Rice’s Seedling peach.......|Mar. 22,713/ 138 44.2 154 51.9
Elberta peach............. Mar. 22,'13| 100 88.0 85 92.9
Jonathan apple............ Mar. 22,713] 34 64.7 33 75.7
Montmorency cherry....... Mar. 22,'13| 176 58.5 184 62.5
Chabot plum.............,. Mar. 22,'13] 236 78.3 183 86.8
 

 

Num- |Percent-
Kind of Buds Date ber age
Buds Killed
Slowly to -16.5° C,
Rice’s Seedling peach....... Mar. 24,'13| 145 57.0
Elberta peach............. Mar. 24,’13} 170 82.9
Jonathan apple............ Mar. 24,'13 39 46.2
Montmorency cherry....... Mar. 24,13) 166 76.5
Chabot plum.............. Mar. 24,’13} 191 100.0
Slowly to -16° C,
Elberta peach............. Nov. 3,’10} 382 77.8
Slowly to -16.59 C
Elberta peach............. Dec. 7,’11); 150 1.3
Slowly to -16.2° C
Elberta peach............. Dec. 7,'11| 210 14.8

 

 

 

 

Num- |Percent-
ber age
Buds Killed
Rapidly to-11.5° C.
158 53.2
86 75.5
40 70.0
189 59.2
176 73.8
Rapidly to-12.5°C.
188 69.1
Rapidly to -16° C.
200 100.0
Rapidly to-16.5°C.
150 96.6

 

 

TABLE 20a.

SHOWING EFFECT OF SLOW AND RAPID TEMPERATURE

FALL ON FREEZING TO DEATH OF PLANT TISSUE.

 

 

Manner Num- |Percent-
Kind of Buds of Date ber age
Freezing Buds Killed
Montmorency cherry....... Slowly to -20° C..|Mar. 2,'12} 163 3.0
Montmorency cherry....... Rapidly to -20° C.|/Feb. 29,712) 130 96.0
Early Richmond cherry..... Slowly to -20° C..|Mar. 9,12) 297 5.0
Early Richmond cherry..... Rapidly to -20° C.|/Mar. 14,’12] 263 98.0

 

TABLE 20b. SHOWING EFFECT OF SLOW AND RAPID TEMPERATURE
FALL ON FREEZING TO DEATH OF PLANT TISSUE.

 

 

Tem- Num- |Percent-

Kind of Buds Date pera- | Time ber age

ture Buds Killed

Ben Davis apple............. Jan. 18,’12} -20.5|2 hrs..... 40 50.0
Ben Davis apple............. Jan. 19,’12] -20.5/2 hrs..... 47 36.2
Ben Davis apple............. Feb. 2,'12} -20 |1)4 hrs... 60 0.0

Ben Davis apple............- Feb. 3,'12| -20 |2}4 hrs... 82 2.44
Jonathan apple.............. Jan. 18,’12| -20.5/2 hrs..... 35 48.6
Early Richmond cherry....... Jan. 18,'12} -21 |1}4 hrs...) 272 98.6
Early Richmond cherry....... Jan. 19,’12} -20.5|2 hrs.....} 200 100.0
Montmorency cherry......... Jan. 19,'12) -20.5/114 hrs...| 178 87.0
Early Richmond cherry....... Feb. 9,'12) -20.5/1% hrs...| 252 100.0
Montmorency cherry......... Feb. 10,'12} -20.5/144 hrs...| 195 94.8
CHEE Wis scis endareie sd os poapacne overs Feb. 15,’12| -20.5)12 hrs....| 132 38.0

(slowly)
Rapidly, +20° C. to -17° C. in 45 minutes

Jonathan apple.............. Feb. 20,13 20 100.0
ermont Beauty pear........ Feb. 20,'13 25 100.0
Chabot plum................ Feb. 20,'13 28 100.0

 

 

 

 

 

 
TABLE 20c.

64

SHOWING EFFECT OF SLOW AND RAPID TEMPERATURE

FALL ON FREEZING TO DEATH OF PLANT TISSUE.

 

 

Tem-
Material Date Time | pera- Results
ture
Elberta peach twigs......... Mar. 21,'13 4 hrs.| -18 |Sap wood and pith
Rice’s Seedling peach twigs..;Mar. 21,'13) 744 hrs.| -18 onlyinjuredregions,
Jonathan apple twigs....... Mar. 21,13] 714 hrs.| -18 Rice’s Seedling
Chabot plum twigs......... Mar. 21,'13| 714 hrs.| -18 | showed the least in-
Montmorency cherry jury. Othersinjured
tWIPS:cegrteea newer ae Mar. 21,'13) 734 hrs.| -18 equally. Killing
Elberta peach about the same for
EWIES sisi discret aco Mee Mar. 21,’13] 134 hrs.| -13.5| twigs whose tem-
Rice’s Y Seedling peach perature fell rapidly
WIGS si divieecarave dee a parsers Mar. 21,13] 134 hrs.) -13.5) to -13.59 and those
Jonathan apple whose temperature
CWAGS sis. gsencoseaee eles ues iaue’e Mar. 21,'13] 134 hrs.) -13.5| fell slowly to -18°
Chabot plum twigs......... Mar. 21,'13] 134 hrs.| -13.5) (Budsinjured worst
Montmorency cherry in rapidly frozen
tWIZSecc ue eee coeur ORS Mar. 21,’13| 134 hrs.| -13.5| ones).
Elberta peach Pith and sap wood
tWIg8. 6.60 cesses em ne aes Mar. 22,'13) 1 hr. -11.5| injured.
Pith and sap wood
Elberta injured. Very slight
peach browning in cortex;
twigs san eure a elec sale atnatererwuers Mar. 22,'13| 734 hrs.| -16.5) none in cambium.
Rice’s No difference in in-
Seedling jury between rapid
peach twigs.............- Mar. 22,'13} 1 hr....] -11.5] and slow. Pith and
Rice’s Seedling sap wood slightly
peach twigs............-+ Mar. 22,'13| 74 hrs.| -16.5) injured in both.
Jonathan Pith injured in both
apple twigs.............- Mar. 22,'13| 1 hr....| —11.5] cases.
Jonathan . No other tissues in-
apple twigs.............. Mar. 22,13] 714 hrs.| —16.5| jured.
Montmorency cherry Pith injured in both
CWIRS a 005» mesons a0 oa wise Mar, 22,'13} 1 hr. —11.5) cases.
Montmorency cherry
CWIPS cass oaiee en eactes te Mar. 22,'13| 71% hrs.| -16.5
Chaber plum Pith and sap wood
EWIGSs 5 ga sais es Sates Mar. 22,'13) 1 hr. -11.5] injured equally in
Chabot plum twigs......... Mar. 22,13] 74% hrs.| -16.5| both cases.

 

 

 

 

 

With these twigs it will be seen that the killing temperature
of rapidly frozen twigs was four and a half degrees higher than that
of the more slowly frozen twigs, and even then the buds of the rapidly
frozen twigs killed the worst.

In rapid freezing it required from one to one and three-fourths

hours to reach a temperature of -20° C.
from seven to ten hours to reach the same temperature.

In slow freezing it required

Many

young fruits and succulent plants were also frozen slowly and rapidly
65

but there was so little apparent difference between the results that
the data are not given. The killing temperature lies so near the
freezing point that possibly the slowly frozen tissue kills badly be-
cause it is exposed to temperatures around the killing point longer.
This tender tissue was exposed to the minimum temperature for
from twenty to thirty minutes.

It will be seen that the rate of temperature fall with winter
twigs and buds exerts the greatest influence on the extent of killing
at a given temperature of any feature we have so far discussed.
And in the case of very forward, rather tendér fruit buds, the rate
of temperature fall exerts great influence. Thus on March 24, 1913,
when all buds, especially of peaches, plums and cherries, had made
much growth, a temperature of -11.5° C. killed as many buds with
rapid temperature fall as a temperature of -16.5° C. with a slower
temperature fall.

Tests were made to see whether the rapid temperature fall
that does the most harm is in the early part of the ice forming state,
or in the later part. The following table gives the results with peach
buds frozen slowly one-half way down to the killling temperature
and rapidly the remainder of the way, and others frozen rapidly one-
half the way down and slowly the remainder of the way, and others
slowly all the way down:
: 66

TaBLE 21. SHOWING THE RELATIVE EFFECT ON THE RESISTANCE
to Low TEMPERATURE OF RAPID TEMPERATURE FALL
Towarp THE BEGINNING AND TOWARD THE END
OF THE FREEZING PERIOD.

 

 

Number |Percent-
Kind of Buds Manner of Freezing Date oO age
j Buds Killed.
Elberta peach.......... Slow to —12; fast -12
LO HN sisces oses eens Dec. 20,'11; 135 3.7
Elberta peach.......... Fast to —12; slow -12
£0 1G sane cia sae Dec. 20,’11) 77 71.4
Elberta peach.......... Slow to -17.5......./Dec. 20,’11} 129 6.2
Elberta peach.......... Fast to -16......... Dec. 8,'13) 135 98.5
Elberta peach.......... Slow to -12; fast to
AG: cecians ae ced os Dec. 8,'11] 113 3.5
Elberta peach.......... Bae to -12; slow to
oa easements oe Dec. 8,'11) 135 29.0
Elberta.............6. Mediuse to -12; fast
TOA 16 oeieiiere te cece Dec. 13,’11] 155 52.3
Montmorency cherry...| Fast to —12; slow to
220) ahi Gc eliecere'si sia 80 Feb. 24,712) 142 75.0
Montmorency cherry...| Slow to —12; fast to
0% seg chars oe ae Feb. 27,12) 136 15.4
Montmorency cherry...| Fast to-20......... Feb. 27,12} 130 96.0
Montmorency cherry...| Slow to -20......... Mar. 2,12] 163 3.0
Early Richmond cherry | Slow to -12; fast to
20 cece coer e Mar. 5,'12| 291 14.0
Early Richmond cherry | Fast to -12; slow to
S20 i riuesé secre: sana ac0l8! Mar. 7,'12| 283 83.0
Early Richmond cherry | Slow to -20......... Mar. 9,’12| 297 5.0
Early Richmond cherry | Fast to -20......... Mar. 14,’12| 263 98.0
Dyehouse cherry....... Slow to -12; fast to
S20 ides aia miss 3% Mar, 16,712) 184 56.0
Dyehouse cherry.......| Fast to —12; slow to
=20). cee seeene see ss Mar. 19,’12} 200 99.0
Dyehouse cherry....... Fast to -20......... Mar. 22,'12} 150 95.0

 

 

 

 

 

It will be seen that rapid falling in the early part of the freezing
period down to -12° C., does more harm than rapid fall in the latter
part of the period, from -12° C. to the killing temperature. This
rapid freezing probably has considerable to do with the amount of
killing at times in nature, though just how much it is difficult to tell.
In this investigation it was not possible to cause, the temperature to
fall more slowly than the most rapid fall to be observed naturally
in the climate of this station. Yet there are probably times when
on sunny, cold days the temperature of some tissue may rise to neat
the freezing point due to the absorption of the heat by the dark color
of the bark. In this case when the sun is off the twigs, the tempera-
67

ture will fall very rapidly. Since rapid temperature fall near the freez-
ing point seems to be more harmful than rapid temperature fall near the
killing temperature, it would seem certain that greater killing should
thus result. It does not seem impossible that ‘‘sun scald”’ of apple
trees may be explained in this way.

This rapid fall of temperature may also be a feature to be con-
sidered in heating an orchard. Thus any one who has worked with
orchard heaters knows that if on a still night a few of the heaters
go out, the temperature will immediately fall to about that which
would prevail without the heaters. In this case it is possible that
the tissue may kill worse than if the heaters had not been there,
since the blossoms or fruit would freeze very rapidly. We can not
be certain of this, however, for results with rapid freezing of blossoms
at this station have not been uniform enough to be conclusive.

Maturity and Hardiness. Probably the greatest factor in deter-
mining the amount of cold that can be withstood by trees and shrubs
that live through the winter is a condition of maturity. Emerson!
‘has studied the question of maturity of fruit and other trees in Ne-
braska and has found that the varieties most hardy in wood are
those that mature early. Where growth can be checked early in the
season, as by a gross feeding cover crop like millet, the trees will
also withstand more cold.

Selby? made a study of the injury to fruit trees and ornamentals
by the severe freeze early in the winter of 1903-4, and attributes
the severe injury to the fact that the trees grew late in the fall on
account of a very wet period following a period of dry weather.

Eustace’ reports a study of the effect of the same winter on
’ fruit trees and describes similar conditions. It seems in this case
also the great injury is due to the trees’ having grown late in autumn.

Winkler‘ found that the resistance of native trees of Germany
is least in May, June, July, and August, and gradually increases
during September, October, November and December, and is great-
est in January, as measured by laboratory freezings.

In summer the fruit buds, for example in August after they can
be easily detected, may be killed by a temperature of -9° to -10° C.
or somewhat lower on some years. At this time there is little differ-
ence between the hardiness of the buds, the wood, and even the foli-
age, though the foliage kills slightly the worst; while in winter fruit

Nebraska . Exp. Sta. Bul. 79, 1903, (Bibl. No. 33); Neb. Agr. Bi Sta. Bul. ae 1906,
Set Wek en N eb. Agr. Ex! =pePt a. Anl. Rpt. No, 19, 1906, pp. 101-10, (Bibl. No. 3
Exp. Sta. B 192, 1908. (Bibl. No. 101).
iNew eric {Gener Agr. Exp. Sta. Bul. 269, 1905. (Bibl. No. 38).
‘Jahrb. f. Wiss. Bot. Vol. 52, 71913, pp. 467-506. (Bibl. No. 121).
68

buds have been known to survive temperatures of -30° C. and lower,
and the tree will survive, under favorable conditions, considerably
lower temperature than that. In fact Macoun! cites an instance
where a Pyrus baccata—Pyrus Malus hybrid—has withstood for
five years a climate whose temperature frequently falls to -50° F.,
and in 1909 it fell twice to -59° F.

At the beginning of winter, as observed by the authors above,
the tree tissue generally—whether it is buds, wood, cambium or
cortex—will stand less cold than later in the winter. Observation
at this station indicates that at least some tissue increases in hardiness
rather rapidly for a short time following leaf fall. The following
table gives the temperature and result of freezing peach fruit buds,
beginning in summer when they are first plainly to be observed and
continuing until January:

TABLE 22. SHOWING THE RELATIVE HARDINESS OF FRuIT BuDs AT
VARIOUS SEASONS OF THE YEAR.

 

Tem- | Number |Percent-
Kind of Buds Date pera- age

°
ture Buds Killed

 

Elberta peach buds..................- July 15,13! - 6 23 78.2
Elberta peach buds................... July 16,713) - 5 47 100.0
Elberta peach buds................04. Sept. 15,711} - 9 186 64.6
Elberta peach buds..............-2005 Sept. 27,’10} -15 245 39.0

Elberta peach buds

Nov. 1,10} ~-16 382 77.8
Elberta peach buds

Nov. 1,’11| - 9 104 60.5

Elberta peach buds.... ..-|Nov. 14,711} -12.5} 188 69.1
Elberta peach buds.. ...|Nov. 12,’09} -13.5] 198 1.5
Elberta peach buds.. -|Nov. 17,’11| -14.5] 133 100.0 «
Elberta peach buds.. Nov. 18,’11} -12.3] 100 91.0
Elberta peach buds Nov. 18,’11} -13.3] 150 99.3

Elberta peach buds
Elberta peach buds
Elberta peach buds
Elberta peach buds

Elberta peach buds Dec. 14,'09} -20.5] 190 74,7
Elberta peach buds Dec. 18,’09} -22 608 48.2
Elberta peach buds Jan. 8,'13] -20 105 51.0

Elberta peach buds
Elberta peach buds

 

Oldmixon peach buds................. Aug. 23,110) - 8.5] 162 93.2
Oldmixon peach buds................. Nov. 26,’09| -18 160 81.2
Oldmixon peach buds................. Nov. 26,'09| -19.5) 229 15.3
Oldmixon peach buds................. Dec. 6,’09} -22 290 93.1
Late Duchess apple buds.............. July 15,’13} - 6 20 70.0
Jonathan apple buds.................. July 15,’13} - 5 53 73.6
Jonathan apple buds.................. Nov. 4,’11] -12.5] 68 48.5
Jonathan apple buds.................. Jan. 18,112} -20.5) 35 58.6

 

 

 

 

 

1Procs. Soc. for Hort. Science, 1912, p. 65. (Bibl. No. 69).
69

The following table gives the result of freezing twigs:

TABLE 23. SHOWING KILLING TEMPERATURE OF TWIG TISSUE AT
DIFFERENT SEASONS.

 

 

 

 

 

Tem-
Variety Date pera- Results
ture
PEACHES

Elberta.............. July 6,13] - 6 | 13 twigs. Cambium dead in 5;
cambium and cortex in 8.

Elbertas.s:s.00naee secs July 17,713) - 5 20' twigs. Cambium and cortex
dead in all.

Young Champion..... July 29,’12) - 5 | Twigs 10” long. All tissue injured
in terminal 6”; slight injury to
cortex only at base of tree.

Champion........... Aug. 5,’12} - 5 | Bark and cambium killed in all
stems.

Belle of Georgia Bark, cambium and sap wood

five years old....... Aug. 29,'12] - 5 killed in all twigs.

Elberta............-. Sept. 24,'12) — 5 Bark, cambium, and outer portion
sap wood killed.

Elberta, Cambium and cortex injured except

one year old........ Oct. 5,'12) - 5 at base of one twig. Only injury to
sap wood was in terminal part of
one twig.

Seedling peach, Twigs injured in cambium and

one year old........ Oct. 8,12) - 5 cortex region.

Elberta iscescice vac ses Oct. 14,'11) - 9.5) 24 twigs. 100% dead. Cambium
only killed.

Elberta............4- Oct. 19,’11] - 5 | 38 twigs. No injury.

Elberta.............. Oct. 21,'11} ~ 7.5] 46 twigs. 73.9% dead. Cambium
only killed.

Elberta.............. Oct. 26,'11/ - 9 | 39 twigs. Killing confined largely
to cambium.

IDOE eisisssisioie « ase adr Nov. 1,’11] - 9 23 twigs. oe 6% killed. Cambium
only injured

Elberta.............- Nov. 2,’11] - 9 51 twigs. 84. 3% killed. Cambium
only injured.

Elbertascsieaestey Ges Nov. 16,12} -15 Slight injury in cortex. Cambium
uninjured.

Elberta nie citrus see's cons Dec. 6,12) -15 Cortex injured in all; cambium un-
injured; pith killed and sap wood
occasionally showed injury.

Seedling, Injured slightly in cortex and pith;

one year old........ Dec. 18,’12} -16.5| _cambium and wood sap uninjured.

Seedling, one year'old |Dec. 19, 42] -18 Injury confined to pith and cortex.

Elberta. .oece0c ee eee Dec. 7. 12] -16 Injury confined to shoulder below
bud and pith region.

Elberta...........605 Jan. 11,’13} -20 | Pith dead, other tissues uninjured.

Rice’s Cortex injured slightly; cambium

Seedling........... Jan. 25,’12} -19.3} entirely killed.
UDertals jccisied-eteree ais Mar. 21,’13) -18 Injury to sap wood and pith.

Rice’s Injury to sap wood and pith less

Seedling........... Mar. 21,’13) -18 than with Elberta.

Elbertas ::<s<00 exes Apr. 5,'13| -12.5) Wood uninjured.
7O

 

 

 

 

 

Tem-
Variety Date pera- Results
i ture
APPLE TWIGS
Jonathan twigs....... May 17,'13) - 4 | Cortex and epidermis hardiest in
‘ = ees art. Near base twigs
ardier than near tip.

Jonathan twigs....... May 24,'13) - 4 Slight injury near terminal part.

Jonathan twigs....... June 7,'13) - 5 Cambium injured throughout all
twigs. In terminal 3 in. injury
extended to cortex, sap wood and
pith. Terminal leaflets more se-
verely injured than remaining
ones,

Ben Davis, ‘a Fi sie aca severe injiry is cambium, cortex

seven years old..... une 26, - and sap wood.

Young Early Harvest. |June 27,'13) - 4 Very eligut injury in cambium near
terminal.

Early Harvest........ June 27,713} - 5 | Cambium, cortex, sap wood and
pith injured. More severe near
terminal.

Ben Davis, Cambium and cortex severely in-

i nye years Oldies ees fay ee - oe ured. Sap wood injured.

ate Duchess......... uly 15,713) - twigs; no injury.

Jonathan twigs....... July 16,’13) - 5 20 twigs; no injury.

Young apple......... July 27,112} - 5 | All tissue injured 4” back from
terminal. No tissue injured far-
ther back than 7” from terminal,
Cortex injured most and cambium
next.

Jonathan............ Aug. 15,12) - 5 Cortex and cambium _ injured
slightly in all samples. Sap wood
and pith not injured. Only
slight difference between younger

; and older parts.

Ben Davis........... Oct. 9,’12} - 8 | No parts killed.

Ben Davis........... Oct. 13,712} — 9.5) No parts killed.

Jonathan............ Oct. 16,'12; -15 Cortex killed; cambium uninjured.

Jonathan............ Nov. 4,’11) -12.5) 23 twigs. No injury.

Jonathan, Slightly injured in cortex. Cambium

one year old........ Nov. 16,’11} -15 uninjured.

Jonathan, 38.5 inches of twigs; 67.5% killed

one year old........ Nov. 27,'11} -20 in all tissues.

Ben Davis, 40.5 inches of twigs; 14.8% killed
one year old........ Nov. 27,11] -20 in all tissues. :
Jonathan, 158 inches of twigs; 34.1% killed

é sae year old........ Nov. 29,’11} -19.4] in all tissues.

en Davis,

one year old........ Nov. 29,’11] -19.4) No injury. 5
Ben Davis, 80 inches of twigs; 7.5% killed in

one year old........ Nov. 29,'11] ~21 all tissues. :

ano, 38 inches of twigs; 7.8% killed in

two years old....... Nov. 29,’11] -21 all tissues. ,
Jonathan, 136 inches of twigs; 59.8% killed in

one year old........ Dec. 5,'11} -20 all tissues. i

Gano, 113 inches of twigs; 15% killed in

two years old....... Dec. 11,'11} -20.7| all tissues.
71

 

 

Tem-
Variety Date pera- Results
ture
PLUM TWIGS
Mature plum tree.... \July 30,’12| - 5 Cambium, pith and cortex injured
throughout. Sap wood slightly
injured throughout.
Marianna............ Oct. 9,'12} - 8 | Very slight injury.
Marianna, New sfioota all killed only in
one year old........ Nov. 8,’11) -11 spots at basal ends.

Marianna, Injury in cortex and pith. Sap
one year old........ Dec. 18,'12} -16.5} wood and cambium uninjured.
Marianna, Injury confined to pith and cortex,
one year old........ Dec. 19,’12] -18 slight injury to pith. Other tissues

uninjured.
Marianna............ Jan. 11,'13) -20 Slight injury to pith. Other tissues
uninjured.

 

 

 

 

Eustace! often observed the greatest injury to peach trees to
be just above the snow line. Following the winter of 1904 Green
and Ballou? reported that an Ohio fruit grower was able to save his
trees by banking the bodies with manure, thus keeping the tempera-
ture of the trunks near the ground from going as low as that to which
the remainder of the tree was exposed.

To test this point at the Missouri Experiment Station, sections
of tissue from young and old trees were taken at different points
along the trunk beginning near the ground and continuing upward
into the branches. These were collected and frozen at intervals
throughout the year beginning in September and ending the follow-
ing July. The results are shown in the following tables:

1New York (Geneva) Agr. Exp. Sta. Bul. 269, 1905. (Bibl. No. 38).
Ohio Agr. Exp. Sta. Bul. 157, 1894. (Bibl. No. 48).
TABLE 24. SHOWING RELATIVE HARDINESS OF DIFFERENT TIssuz,

72

 

 

Tem- Location
Variety Date pera- of Results
ture Tissue

Ben Davis Sections taken at | Current  sea-
apple tree intervals from | son’s twigs
sections.........0. Sept. 4,’12) -5 near the ground] entirely free
to the twigs...... from injury.

In the older

wood injury

was slight

and confined

to cambium

and outside

part of sap

wood. The

lowest part of

trunk had

cambium

more severely

injured than

parts higher

up.

Sections from eight Sections taken at | Injury most
year old Improved intervals from severe in cam-
Janet apple tree... |Sept.11,'12) -6 near the ground | bium region.

Sections from five
year old Improved
Janet apple tree....

Ben Davis apple,
seven years old,
2 in. in dia. at
CrOWN..........04.

Sept. 12,'12

June 26,'13
June 26,'13

 

 

-5
-5

 

to the twigs.

Sections taken at
intervals from
near the ground
to the twigs.......

Crown (highest
point where roots
attach 6 in. below
surface).........
6 in. above crown

 

(surface of soil)

Younger
stems less
browned than
older. Sap
wood injured
in 50% of
stems, great-
est injury on
most rapidly
thickening
side of stem.
Older —_ wood
from near
ground decid-
edly more
brown than
younger wood
of twigs. Cor-
tex showed
first injury

and greatest. *:

Cambium in-_

jury slight.
Sap wood
injury co-
fined to older
wood.

All sections
from _ lowest
to highest in-
jured in cam-
bium. l

Sat
73

 

 

Tem- Location
Variety Date pera- of Results
ture Tissue

Same, 184 in. in dia. above two

at crown.......... June 26,713) —-5 12 in. above crown.| feet also in-

Same, 15 in. in dia... |June 26,713) —5 18 in. above crown.| jured in cor-

Same, 1% in. in dia.../June 26,"13} -5 24 in. above crown.| tex. All sec-

Same, 144 in. in dia.../June 26,'13| —-5 36 in. above crown.| tions above

Same, 1__ in. in dia.../June 26,13) -4 48 in. above crown.| four feet in-

Same, 5% in. in dia...|/June 26,13) —-5 60 in. above crown.| jured in cam-

Same, Min. in dia...|June 26,'13] —-5 72 in. above crown.| bium, cortex
and sap wood.
The crown
was hardiest
and the high-
er up from
the crown
showed the
more injury.

Ben Davis apple, Cambium

five years old, slightly
3 in. in dia......... July 2,713} -4.5) Crown............ injured.
Same, 244 inin...... Cambium
LAs ecividoisied saa oe July 2,'13} -4.5) 6 in. above crown.. slighely in-
jured.
Same, 23¢ in. in Cambium in-
Bess acerca toie Sas a eis July 2,’13) -4.5) 12 in. above crown.| jured.

Same, 2 in. in Cambium = se-

Mas bacieengciane sien July 2,'13} -4.5] 18 in. above crown.| severely

; injured.
Same, 1)4 in. in Cambium _§se-
lAscwecaae sa we tsa July 2,'13} -4.5] 24 in. above crown.| verely injured
7 cortex slight-

ly injured.
Same, 1 in. in Cambium se-
as: sa eutehedane seat July 2,13) -4.5] 36 in. above crown.| verely injured
cortex slight-
ly injured.

Same, 1 in. in dia.....|July 2,13 .5| 48 in. above crown.| Cambium and
cortex severe-
ly injured.

Same, 34 in. in dia....|July 2,13] -4.5] 60 in. above crown.| Cambium and
cortex severe-
ly injured;
sap wood
slightly in-
jured.

Same, 14 in. in dia....|July 2,'13) -4.5| 72 in, above crown.| Cambium and
cortex severe-
ly injured;
sap wood
slightly in-
jured.

Same, 1 in. in dia....|July 2,'13] -4.5] 84 in. above crown.| Cambium and
cortex severe-
ly injured;
sap wood
slightly —in-
jured.

Same, in. in dia...|July 2,713} -4.5] 96 in. above crown.) Cambium, cor-

 

 

 

 

tex and sap
wood severely
injured.
74

 

 

Tem- Location
Variety Date pera- of Results
ture Tissue
Early Harvest Buds largely
apple, 10 in. in dia../Sept. 28,712} -6 Near ground...... killed, bark
Same, 7 in. in dia.....|Sept.28,'12} -6 | 48in. above ground| and cambium
Same, 3 in. in dia...../Sept. 28,12} -6 | 96in. above ground] taken near
Same, 1 in. in dia...../Sept. 28,'12] -6 12 ft. above ground sround se-
Same, % to 4% verely in-
in. in ie aoe... |Sept. 28,712) —-6 15 ft. above ground] jured. The
(includes _ this very young-
year’s growth) est wood
showed little
or no injury.
In the wood
near the
ground, the
browning was
uniformly dis-
tributed. In
wood higher
up the brown
was irregular
and in spots,
In the young
wood, cam-
bium appear-
ed normal—
only ere
injured.
Jonathan apple, ;
four years old...... Oct. 19,12; -7 | At ground........ No injury
Same, four years old../Oct. 19,’12| -7 12 in. above ground] No injury.
Same, four years old..|Oct. 19,°12 -7 | 24 in. above ground] No injury.
Same, four years old..|Oct. 19,"12 -7 | 36in. above ground] No injury.
Same, four years old..|Oct. 19,"12 -7 | 48 in. above ground] No injury.
Same, four years old..|Oct. 19,°12 -7 60 in. above ground] No injury.
Same, four years old..|/Oct. 19,"12 -7 72 in. above ground] No injury.
Same, four years old..|Oct. 19,"12 -7 | 84in. above ground) No injury.
ronae: ue years old..|Oct. 19,’12/ -7 | 96 in. above ground ae in
onathan apple, wood, ex-
four years old, cept 4 in. in
Z 2% pire didi: sess Oct. 23,712) ~9 | At ground........ dia. or small
ame, in, er, injured.
- in a Bes Gea Bees Oct. 23,'12) -9 12 in. above ground! The Ses
ame, 15% in. seve rely
in dia............. Oct, 23,12) -9 | 12in. above ground] browned sec-
Same, 1 in. in dia..../Oct. 23,'12) -9 | 36in. above ground| tion was 2 ft.
: ° aboveground,
Same, 13 in. at the crotch
in dia........ :+-+-/Oct. 23,712) -9 | 24in. above ground] of a rapidly
Same, .8 in. in dia... ./Oct. 23,12} -9 | 48 in. above ground growing
Same, .5 in, in dia..../Oct. 23,12} -9 | 60 in. above ground branch. The
Same, 4 in. in dia.. ..JOct. 23,'12) -9 72 in. above ground| section at the
Same, 4 in. in dia....|Oct. 23,12) -9 | 84 in. above ground| ground was
Same, ,*% in. in fess injured
LA setae wore wane eave Oct. 23,712) -9 | 96 in. above ground] than the one
(Last 4 new 1 foot above.

 

 

 

growth)

 

Cortex, cam-
bium and sap
wood injured.
75

 

 

 

 

 

 

. Tem- Location
Variety Date pera- of Results
i ture Tissue

Jonathan apple, Most severely
four years old...... Nov. 14,712} -12 | At ground........ injured. Cam-
bium cortex
and sap wood

injured.

Jonathan apple, Cambium in-

four years old...... Nov. 14,'12} -12 | 6 in.{above ground.| jured. Cor-
tex slightly
injured.

Jonathan apple, Cambium in-

four years old...... Nov. 14,12} -12 | 12 in. above ground} jured. Cortex
slightly _in-
jured.

Jonathan apple, Nov.-14,’12| -12 | 18 in. above ground) Cambium _in-

four.years old...... jured. — Cor-
tex slightly
injured.

Jonathan apple, five

years old. (Thickest All tissue in-
part of trunk, 3 in. jured severe-
in diameter)....... Jan. 15,’13| -20 | At’crown......... y.

Same ey oases siete cde es Jan. 15,’13| -20 | 3 in. above crown All Hssue in-
jured.

GORING saving ida Grass asus sie Jan. 15,’13} -20 | At level of ground.} Slight injury
in bark; none
in cambium;
sap wood in-
jured.

SAMECs is sss sie Reive as Jan. 15,’13] -20 | 3 in. above ground | Injury in same

. tissue as
above, but

Jonathan apple, five not quite so

years old. (Thickest severe.
part of trunk, 3 in.
in dia.)............ Jan. 15,’13) -20 | 6 in. above ground.|Same as above.

DAME: vi ae howe eee em Jan. 15,’13] -20 | 12 in. above ground} Sameas above.

DAME. do sscieis cede tres oe Jan. 15,’13} -20 | 18 in. above ground] No injury in
cortex or cam-
bium; sap and
heart wood
slightly  in-
jured.

Jonathan apple, five . ‘

yearsold. (Thickest All tissue in-
part of trunk, 3 in. jured severe-
In dia.)..........85 Jan. 20,'13} -15.5} At crown......... ly.

AMIE sic in esas 5 eer aeaia eae Jan, 20,13} -15.5) 3.in. above crown | All tissue in-
jured slightly
less than
above.

Sameyes gee saeaahenas Jan. 20,13] -15.5) At ground........ Injury in cor-
tex region.

Jonathan apple, five ‘ i

yearsold. (Thickest Slight injury
art of trunk, 3 in. in cortex
in diameter)....... Jan. 20,713] -15.5} 3 in. above ground| region.
76

 

 

Tem- Location
Variety Date pera- of Results
ture Tissue

Same ia: ssiete sca eee ein Jan. 20,’13) -15.5] 6 in. above ground.| Very slight in-
jury in cor-
tex region.

Sa ti Goes soe sue ears alere Jan. 20,713} -15.5] 12 in. above ground] No injury.

Jonathan apple, Severe injury

five years old...... Mar. 25,’13] -12.5) At crown......... in cortex,
cambium and
sap wood.

SaMe.eascsacevenese Mar, 25,713} -20 At crown......... Very severe in-
jury in cor-
tex, cambium,
and sap
wood,

SAME sil cou asi eieees Mar. 25,’13) ~12.5) 3 in. above crown..) Injury in cor-
tex, cambium
and sap wood
less severe
than at crown

Same. ccs tees Mar. 25,13) -20 | 3 in. above crown..| Less severe in-
jury than at
crown.

Same sees siows ones Mar. 25,13} -12.5| 6 in. above crown..| Very slight in-
jury in cortex
and cambium,

SAMI aise esses siaieienn es Mar. 25,'13| -20 | 6 in. above crown..| Less severe in-
jury than
above in same
regions.

AIMS ate oatieains were Mar. 25,’13} -12.5| 3 in. above ground.| No injury.

Same...........002- Mar. 25,’13] -20 | 3 in. above ground.) Very slight in-
jury in cor-
tex.

Same | oes salgiovates Mar. 25,'13] -12.5] 6 in. above ground.| No injury.

Same eaustone gases Mar. 25,'13} -20 | 6 in. above ground.| No injury.

SAME) wed cows we RS Mar. 25,13} -12.5] 9 in. above ground.| No injury.

SAME enscie ote ese eens Mar. 25,’13} -20 | 9 in. above ground.| No injury.

SAM Cleef aisscsRdacess olons Mar. 25,'13, -12.5/ 12 in. above ground No injury.

SAMO ects sioeik ence ei Mar. 25,’13] -20 | 12 in. above ground| No injury.

Same............... Mar. 25,'13] -12.5] 18 in. above ground] No injury.

SAMO ee eis ne e sted aie Mar. 25,’13| -20 | 18 in. above ground| No injury.

 

 

 

 

 

It will be seen that the part of the trunk that most slowly de-
velops hardiness on approach of winter is that near the surface of
the ground and near the junction of rapidly growing limbs. All the
tissue at the lower part of the tree is more tender in early winter

than is the upper portion.

Of course this might not be true on other

seasons. The autumn of 1912, however, was a normal one, the wood
apparently going into winter in a well ripened condition. In June
and early July the wood in the upper portion of the -tree is most
tender. It is also interesting to note that in June and July when the
77

tissue is generally most tender, the tissue near the base of the tree is
most hardy.

Selby! observed that the great tenderness in the early part of
the winter is probably due to a greater moisture content. He ob-
served that the cambium in winter during the time when plants are
very hardy, isin a much dried out condition andin normal seasons has
to some extent reached this condition by the time of the early freezes,
but in seasons like that one preceding the winter of 1903-4 it is still
in a somewhat succulent condition when the early freeze comes.

It is well known that seeds in a dry condition will withstand
very much lower temperature than when they have absorbed moist-
ure. Thus Schaffnit? reduced the germination percentage of wheat
from 100 to 40 by soaking it in water for eight hours at room tem-
perature. In twigs it is probable that a dry condition is essential
to the hardiness of the cambium. Shutt? and also Allen* seem to
find a relation between moisture content and hardiness of apple
twigs. However, it does not seem that the increase in hardiness
of other tissue than cambium, at least of cortex, during early winter
can be explained by a decreasing moisture content.

During the winter of 1912-13, beginning November, twigs of
apple, peach, plum and cherry were scraped, the cortex ground,
weighed carefully, evaporated to dryness in a water bath (to which
later glycerine was added to raise the boiling point in the water
jacket and thus raise the temperature), and weighed at intervals of
two to three days until a constant weight was reached. Samples
were taken again in January and again in May. No samples were
taken when the tissue was frozen, since then the percentage of mois-
ture would be smaller. The evaporated moisture could not be re-
placed from below. The following table gives the results:

1Ohio Agr. Exp.Sta. Bul. 192, 1908. (Bibl. No. 101).

2Mitt. Kaiser Wilhelm Inst. Landw. zu Bromberg, Vol. 3, No. 2, pp. 93-113, 1910.
(Bibl No. 98).

*Procs. and Trans. Roy. Soc. Canada, ser. 2, Vol. 9, pp. 149-153. (Bibl. No. 104.)

‘Master's Thesis, lowa Agr. Exp. Sta. (Bibl. No. 2).
78

TABLE 25. SHOWING THE MOISTURE CONTENT OF THE CORTEX IN
NOVEMBER, JANUARY AND May.

 

Weight | Weight Per- | Average

Material Date Fresh Dry cent- |Percent-

Sample. | Sample. age age
Grams | Grams | Water | Water

 

|

onathan apple, entire twig.|Nov. 15,712; 36.45 17.15 52.95
ae apple, entire twig. /Nov. 15,'12; 35.82 16.75 53.52 53.24
Elberta peach, entire twig....,Nov. 15,’12; 26.10 12.35 52.61
Elberta peach, entire twig....,Nov. 15,712; 28.84 13.85 51.98 52.33

Jonathan apple, buds, bark

 

and cambium............ Nov. 27,'12; 30.05 13.60 54.70
Jonathan apple, buds bark

and cambium............ Nov. 27,112! 29.95 13.40 55.60 | 55.2
Elberta peach, buds, bark

and cambium........... Nov. 27,'12; 30.15 13.25 56.00
Elberta peach, buds, bark

and cambium............ Nov. 27,'12| 30.00 13.05 56.50 | 56.3
Jonathan apple, buds bark

and cambium............ Jan. 11,113) 25.00 12.25 51.00
Jonathan apple, buds, bark

and cambium............ Jan. 11,13} 25.00 12.10 | 51.60 | 51.3
Elberta peach, buds, bark

and cambium............ Jan. 11,13) 25.00 10.65 57.40
Elberta peach, buds, bark

and cambium............ Jan. 11,713} 25.00 11.10 55.60 | 56.5
Jonathan apple, entire twig.|May 3,’13/ 20.00 8. ‘
Jonathan apple, entire twig.|May 3,’13/ 20.00 8.80 | 56.80 | 56.15
Elberta peach, entire twig....|May 3,'13/ 20.00 9.
Elberta peach, entire twig....,;May 3,'13} 20.00 9.00 55.00 54.63

 

 

 

 

 

 

It will be seen that there is no constant difference in moisture
content of the twig cortex from November to May. The difference
in the hardiness of the cortex can not be accounted for by the differ-
ence in the moisture content, but must be accounted for in some
other way. The suggestion is sometimes made that a greater sap
density of the twig and other tissue during winter might account
for this greater hardiness. It was not possible with our apparatus,
at least, to secure sap from the sap wood. The cortex, however,
shows this increase in hardiness to a slightly greater extent than
does the sap wood. The following table shows the cortex sap density
of apple and peach twigs at various seasons of the year, through a
period of three years:
79

TABLE 26. SHOWING Sap DENsITY oF APPLE AND Praca TwIics
THROUGHOUT THE YEAR AS MEASURED BY THE FREEZING
Point DEPRESSION.

 

 

 

 

Elberta peach |Jonathan apple | Gano apple
Date
Depression Depression Depression
JANUAT YS <csh eile. es ele ete 1.902 2.054 1.630
February.............. 1.841 2.170 No data
Mareh es gsi tnvesiaoeacaeans 1.758 No data 1.616
Alprilses c.2cnics cutis eaaesirs 1.765 1.055 .949
MY esses oveia cia ayecesierd wes 1.055 0.915 1.085
JUNG eeceenaeeel oss 1.263 1.415 1.289
Mile caiiaiatuceins cael 1.252 1.500 1.469
AUCUSt sie decane saiare nee 1.652 1.623 1.570
September............. 1.748 1.605 1.690
Octobernwcccs see saee nes 1.743 1.892 1.728
November............. 1.765 1.924 1.665
December.............. 1.694* 2.016 No data

 

 

 

*Only one depression taken in December.

It will be seen that while the sap density of the cortex of winter
twigs is much greater than that of early summer twigs, yet it is not
appreciably greater than that of twigs in late September and October,
when the tissue is still considerably more tender than in December
and January. Some may suspect that the low sap density of the
early summer twigs may be due to their young and somewhat succu-
lent condition. It may be said, however, that the density of the
cortex of these young twigs is generally greater than that of any
other tree tissue except the leaves. (Data to be published in another
bulletin). It would seem certain then that while a part of the increased
hardiness of tree tissue in winter may possibly be accounted for by
the greater sap density, not all of it can; certainly not the greater
hardiness of December tissue over that of October. '

In the case of plants killing at as low temperature as those at which
winter twigs kill, it seems possible that the sap solute, if it remains
in solution, may tend to keep a small amount of water unfrozen
and thus protect the protoplasm to some extent. If this should
be true, the eutectic point of the sap solute would play a very import-
ant part in determining the amount of killing. Some efforts were
made to determine whether or not there may be changes in the sap
solute as winter comes on that give it a lower eutectic point. Just
at the time of leaf fall or slightly before, twigs had the cortex scraped
80

from them and the sap expressed in large enough quantities that it
could be evaporated down to one-fourth to one-eighth of its volume
and leave enough for freezing point determinations with a Beckmann
thermometer. The evaporating was done in a dry oven where the
temperature never was above 50° C. The evaporating was done in
broad, shallow dishes and was generally accomplished in one day.
There was apparently no fermentation. In all cases sap taken in
October or early November would be thick and gummy long before
it could be concentrated to one-sixth of its original volume. It was
noticed that it was very difficult indeed to filter the sap from the twigs
in autumn or very early winter, while sap taken in December or Jan-
uary or later, filtered much more easily and could be concentrated
to one-sixth to one-eight of its volume. In this case it would stay
in solution at temperatures as low as could be secured with salt and
ice; that is, temperatures low enough to kill many peach buds, indi-
cating that there is certainly a probability that at least a part of the
sap solute remains in solution at a temperature low enough to hold
water unfrozen to protect the protoplasm. Of course in the earlier
season the solidifying of the liquid may be due to colloidal substances
in large quantities, and it is entirely possible that the solute had just
aslowaneutectic point. It was not possible to determine the eutectic
point by keeping temperature records since no apparatus was availa-
ble other than the Beckmann thermometer which could not be used
without changing the setting several times, for such low temperature.

It would seem highly probable that, except in the case of cam-
bium, the additional hardiness acquired by the different tissues of
the tree as they pass into winter, is a change in the protoplasm such
that it can withstand the great loss of water rather than a change in
the percentage of moisture or in sap density. It is also possible
that changes in the sap solute that lower its eutectic point may occur
and that these may increase the resistance to cold by holding water
unfrozen to protect the protoplasm from too complete desiccation at
lower temperatures.

Rate of Growth and Hardiness. At the time of most rapid
growth of deciduous plants in early summer they are generally most
tender. Whether this is because they are furthest from the con-
dition of maturity they acquire in autumn and early winter, or be-
cause of the very low sap density at this time, it is not easy to say.
In some cases the young tissue is most hardy. Thus Goeppert
found young leaves more hardy than older ones. Apelt! found the

Cohn. Beitrage z. Biol. d. Pfl. Vol. 9, p. 215. (Bibl. No. 3).
81

young outer ends of potato shoots to withstand lower temperatures
than would the older basal portion. ‘Rein! found young onion leaves
more hardy than older ones. Winkler? found young one-year-old
needles of evergreens more hardy than older ones. Shumacher?
found young yeast cells more hardy than older ones. Fisher* found
newly formed colloids to regain their normal characteristics after
being exposed to a low temperature that would irreversibly change
older colloids. On the other hand Bartetzko® found that young
cultures of Aspergillus niger would not withstand as low temperatures
as would older ones. It seemed worth while to make some freezings
to determine whether or not plant tissues making rapid growth are
generally frozen to death at higher temperatures than are tissues
growing more slowly. Leaves of various plants were used, leaves
that were certainly full grown—in case of those from fruit trees—and
leaves that had apparently ceased growing, in case of plants like
lettuce, cabbage, kale, etc., were frozen at the same time with young
rapidly growing leaves from near the growing tips of the stem. The
following table gives the results:

1Zeits. f. Naturw. Vol. 80 (1908) p. 1. (Bibl. No. 92).
2Jahrb. f. Wiss. Bot. Vol. 52, 1913, pp. 467-506. (Bibl. No. 121).
ing der Math. Phys. Klasse d. Wiener Akad. d. Wiss. Alt. 1, 1874. (Bibl. No.

‘Beitr. Biol. der Pfl. Vol. 10, pp. 133-234, 1911. (Bibl. No. 40).
Jahrb. f. Wiss. Bot. Vol. 47, pp. 57-98 (1911). (Bibl. No. 8).
82

TABLE 27. SHOWING THE RELATIVE HARDINESS OF YOUNG RAPIDLY
GROWING LEAVES AND OLD Mature LEAVES.

 

Material

Date

Tem-
pera-
ture

Results

 

Jonathan apple twigs
thawed slowly......
Jonathan apple twigs
thawed rapidly.....

Jonathan apple.......

Young Jonathan

Jonathan apple.......

Salway peach.........
Elberta peach twigs....

Elberta peach........

Grape shoots.........

May 17,'13
May 17,'13

May 24,'13

June 7,13

June 12,13

May 24,'13
June 7,'13

June 12,'13

May 24,'13

 

 

-4
-4

-4

 

2 small terminal leaflets of each

of the 4 twigs were injured.
2 twigs had 4 terminal leafletsin-
jured; 1 twig had 5 end leaves in-
jured; 1 twig had 6 end leaves in-
jured. All mature leaves were un-
injured,

Slight injury in terminal part. Ma-
ture leaves uninjured.

Terminal leaflets injured. Mature
leaves green and turgid: slight in-
jury being confined to leaf veins.
In terminals, 2 to 5 in. of the twigs,
cortex, cambium, sap wood and
pith were severely injured, cortex
and pith being hardier. Older
portion was much hardier.

In freezer with peach on same date.
Injury not so great as that to
peach, but younger terminal leaves
showed considerable injury while
older leaves at the base of the twigs
were uninjured.

Very slight injury in terminal part.
Mature leaves uninjured.

All terminal buds killed. Mature
leaves, including those below 2 in.
of terminal, had mid-ribs and veins
killed, with other tissues apparent-
ly uninjured. Small leaves ad-
joining large old leaves uninjured.
In terminal 3 in. all tissues were
injured. Of the remaining portion
only the cambium showed severe
injury.

Slowly and rapidly growing twigs
were used. Only 2 to 3 terminal -
leaves of the slowly growing twigs
showed injury, while on the rap-
idly growing twigs 7 to 8 terminal
leaves were entirely killed. Oldest
leaves at base of all twigs were un-
injured.

Youngest 10 leaves of 8 in. shoot
dead. Mature % of 18 in. shoot
uninjured.

 
 

 

 

 

Per- /Percent-
; Tem-|Num-| cent- age De-
Material Date pera- | ber age Leaves | pres-
ture |Leaves} Surface all sion
Injured | Killed
Black Seeded Simpson
lettuce young leaves... |June 11,’13] -4 18 33.3 16.6 0.520
Black Seeded Simpson
lettuce old leaves...... June 11,’13] -4 40 79.3 70.0 | 0.575
Black Seeded Simpson
’ lettuce young leaves... |June 12,113] -4 12 83.3 50.0
Black Seeded Simpson
lettuce old leaves...... June 12,'13} -4 | 17 30.8 11.7
Tomato leaves, old and
turgid esicctscate eee i June 24,'13] -3 32 72.65 50.0
Tomato leaves, young and
GUT LI eis ceeratsnieve pha: acs eet June 24,’13! -3 30 63.30 | 30.0
Flat Dutch Cabbage,
_ young leaves.......... June 13,’13} -5 10 100.0 100.0
Flat Dutch Cabbage,
old leaves............. June 13,13] -5 4 100.0 100.0
Flat ‘Dutch Cabbage,
young leaves.......... June 14,’13] -3 3 0.0 0.0
.Flat Dutch Cabbage,
old leaves............. June 14,13) -3 4 87.4 75.0
Red Rock Cabbage
young leaves.......... July 1,'13) -4 5 100.0 100.0
Red Rock Cabbage, old
LEAVES joie sists icscuneid eee July 1,713) -4 5 5.0 80.0
'Cowpeas.......... .....{June 14,'13) -3 6 Leaves all dead; stems

(plants)} alive. Old and young
leaves equally injured.
Young stems dead; old
stems alive.

Young tobacco leaves,

2-12 cm. in length..... July 12,’13] -2 5 20.0
Old tobacco leaves, 20-40
em. in length.......... July 12,’13} -2 5 75.0
Young tobacco leaves, ‘
2-12 cm. in length..... July 12,713) -2.5 5 75.0
Old tobacco leaves, 20-40
em. in length.......... July 12,'13) -2.5 5 90.0 :

 

 

 

 

 

In case of apples and peaches the young leaves are uniformly
more easily killed, while in the case of some of the succulent plants
there is little or no difference. In case of lettuce the young leaves
are certainly the more resistant. The density of the sap of the old
peach leaves was such that an average of ten freezing point deter-
minations gave a depression of 1.931 while for the young leaves the

‘. depression was 1.663. With the Jonathan apple, the depression for old

leaves was 1.849 while for young leavesit was 1.202. With these leaves
then it seems that the greater sap density will explain the greater
84

hardiness of the older leaves. In fact the following table, giving
results where twigs with young leaves were placed in cane sugar and
glycerine solutions, indicates that increasing the sap density of the
young leaves to that of the old leaves will increase their hardiness
to nearly that of the old leaves.

TABLE 28. SHOWING RELATIVE HARDINESS OF YOUNG AND OLD
APPLE LEAVES AND OF YOUNG LEAVES THAT HAD
ABSORBED GLYCERINE AND CANE SUGAR.

 

 

Num-| _ Per- Per-
Age Tem-| ber cent- cent- De-
of Treatment Date pera- of age age pres-
Leaf ture |Leaves| all Surface | sion
Killed | Killed
Old....| Water 30 hrs....|July 8,’13}| -4 20 0.0 55.00 | 1.480
Young.| Water 30 hrs..../July 8,’13} -4 26 50.0 82.70 | 1.340
Young.| Cane sugar 3 hrs
(LOY) sdecewe ss July 8,’13) -4 18 11.1 34.90 | 1.818
Young.| 10 %Glycerine
BRE ss aaenees July 8,'13) -4 26 0.0 5.70 | 3.400
Old..... Fresh. 3 leas soscaceis July 12,'13) -4 20 0.0 17.50) .....
Old Water.......... July 12,’13) -4 20 0.0 28.70 | 1.540
Young.| Fresh.......... July 12,’13} -4 19 26.3 48.70] .....
Young.| Water.......... July 12,’13) -4 21 71.4 91.70 | 1.230
Young.| Cane Sugar..... July 12,'13) -4 22 27.2 48.90 | 1.792
Young.| Glycerine....... July. 12,13) -4 22 22.7 32.90 | 3.400
Old....) Fresh.......... July 12,’13) -7 20 35.0 46.20] .....
Old....) Water.......... July 12,’13| -7 20 80.0 85.00 ; 1.540
Young.} Fresh .......... July 12,'13) -7 22 77.7 94.30] .....
Young.| Water.......... July 12,’13} -7 22 |: 100.0 100.00 | 1.230
Young.| Cane sugar......|July 12,’13) —-7 19 57.9 89.40 | 1.792
Young.| Glycerine....... July 12,’13| -7 27 44.1 69.40 | 3.400

 

 

 

 

 

 

 

 

In case of lettuce, however, the depression for old leaves was
0.575, and for young leaves 0.520, and the young leaves are the most
resistant to the low temperatures. It is possible that the waxy
or oily covering on the surface of the young lettuce leaves increased
their resistance to low temperatures. In our experience leaves and
fruits dipped in glycerine or paraffine have been uniformly more
resistant than have tissues not so treated.
85

EFFECT UPON HARDINESS OF PREVIOUS EXPOSURE TO
TEMPERATURE SLIGHTLY ABOVE THE
KILLING TEMPERATURE.

Closely related to the questions of the relation of maturity
to hardiness, and the relation of the rate of growth to hardiness,
is the relation of exposure to low temperature, above that at which
the plants may kill, to hardiness. In fact these problems are so
intertwined that it is difficult, if not impossible, to separate them.
Thus in case of the greater hardiness of roots kept in cold storage as
compared with those kept in warmer places, unquestionably maturity
plays a large part but it is not impossible that exposure to cold also
had its effect. However, by referring to Table 14 it will be seen that
there was little difference among the killing of roots kept in cold
storage at a temperature of 31° F., those kept frozen up in the soil, and
those kept at a higher temperature in our basement storage room.
The relation of exposure to cold to hardiness of winter buds and
wood may also be confused with the rate of temperature fall. This
problem will be discussed for peach buds in a later part of this paper.
In case of some succulent plants, however, the temperature at which
they grew must exert an influence on their hardiness. Thus when
cabbage, kale and lettuce were grown out of doors in late autumn
or early winter, their hardiness was increased over those grown in
the greenhouse more than can be explained by the increased sap
density. At least their hardiness was increased more than the same
increase in sap density brought about by any other means would in-
crease it. When these plants were grown out of doors in early spring
or late autumn, it required a much lower temperature to kill them
than was required in June or July. On the other hand, plants like
tomatoes or cowpeas are influenced in hardiness but slightly by the
temperature at which they grow.

Goeppert! found little increase in hardiness due to continuous
exposure to low temperature with tender tropical plants, but there
was such adaptation with more resistant plants. Apelt? found that
potatoes kept at a temperature of 22.5° C. four to seven weeks were
killed at -2.14° C. while potatoes kept at 0° C. for the same length
of time killed at -3.08° C. Rein? found that a rather large list of
very tender plants kept at a temperature of 8° C were not apprecia-

1Ueber die Warmeentwickelung in dem Pflanzen, etc, book, 1830. (Bibl. No. 44).
2Cohn’s Beitrage z. Biol. d. Pfl. Vol. 9, 1907, p. 215. (Bibl. No. 3).
‘Zeits. f. Naturw. Vol. 80, 1908. p. 1. (Bibl. No. 92).
86

bly hardier than when kept at a temperature of 20° C., while more
resistant plants were considerably more hardy when kept at a low
temperature. Fisher’ found that it required a lower temperature
to change the nature of colloids like starch paste that had been kept
at low temperatures than to change the nature of colloids kept
at a high temperature.

Relative Hardiness of Different Tissues at Different Seasons
of the Year. Whentreesare in a rapidly growing condition, appar-
ently the most tender part of the wood tissue is the cambium and the
young cortex, and sap wood cells. However, in winter after the
wood has reached its greatest maturity, this is not the case. In fact
when severe cold comes, the first tissue to kill seems to be the pith
in the case of young twigs, and there will be browning in the sap
wood and part of the cortex. In case of the cortex the browning is
generally worse in the outer or older cells. This was observed by
Eustace” on peach trees following the winter of 1903-04. We have
often observed the same in artificial freezings we have made, as well
as on peach trees badly injured in winter. Peach trees so injured
that the sap wood seemed practically all browned have, under favora-
ble conditions, had the cambium form new layers of sap wood sur-
rounding this wood. This injured wood soon becomes entirely dead
and the tree depends on the new sap wood formed for conductive
tissue. We have also observed dead areas of bark following the win-
cer of 1911-12 when underneath there was healthy new bark and
healthy cambium. In these cases, at least, the cortex was more
tender than the cambium.

The fruit buds of the peach in late summer during the grow-
ing season are generally about as hardy as the cortex and cambium,
or sap wood of the twigs, though perhaps slightly less hardy than the
same tissues in older wood; while in winter under normal conditions,
at least with peaches, the fruit buds are generally somewhat less
hardy than any of the wood tissue, with the possible exception of the
pith cells. However, in the case of a cold wave that comes on very grad-
ually, say during a period of two or three weeks with a very cold
night at the end, some of the buds may survive a temperature low
enough to kill the sap wood badly. Thus following the winter of
1904-5, when the temperature at Columbia went to -25° C. after
several weeks of very cold weather, nearly all of the peach trees
had a few live buds left while the wood was very badly damaged; and
in the case of peaches in New York following the winter of 1903-04,

1Beitr. Biol. der Pfl. Vol. 10, pp. 133-234, 1911. (Bibl. No. 40).
2New York (Geneva) Agr. Exp. Sta. Bul. 269, 1905. (Bibl. No. 38).
87

Eustace observed that the trees may be badly injured and yet enough
fruit buds left for a full crop of fruit. This last, however, was the
condition when the tissue of the tree had not reached the proper
maturity before the cold period came. The fruit buds seem, some-
times at least, to reach about their maximum condition of maturity
more quickly than wood tissues, especially that near the base of the
tree. Tables 23 and 24 give some information as to the relative
hardiness of other tissues, and the following table gives the result
of some additional freezings where buds were frozen in comparison
with other tissues:

TABLE 29. SHOWING RELATIVE HARDINESS OF DIFFERENT TISSUE,
INCLUDING BuDs, AT DIFFERENT SEASONS OF THE YEAR.

 

: Tem-
Variety Date pera- Results
ture

 

Elberta peach twigs...|July 15,'13} -6 23 buds, 78.3% killed. 10 twigs 7
injured in cambium. 3 in cam-
bium and cortex.

Elberta peach twigs...|July 16,’13| -5 50 buds, 100% killed. 20 twigs,
all injured in cambium and cortex.

Elberta peach twigs, 37 buds, 100% killed. Roots, dead
buds and sections of in cambium and cortex. Wood
WO0d nasecars oe ta x July 28,713) -5 just above ground, severely in-

jured in cortex and cambium. 4
feet from ground, same as above.
This years’ growth, same as above.
Sap wood and pith of youngest
portions dead.
Champion peach twigs 95% of leaf surface dead. Cortex
10 in. long......... July 29,'12) -5 injured 6 in. back of terminal.
Cambium, pith and sap wood in-
jured to 8 in. back of terminal.

Belle of Georgia peach Buds, 100% killed. Young sap
tree, five years old; wood and cambium killed in all
sections of trunk sections. Least injury to bark
and limbs.......... Aug. 29,'12) —-5 was in three year old wood. Bark,

cambium and sap wood killed in
: twigs.

Elberta peach tree, Buds 100% injured. Bark cam-
buds and twigs and bium and outer portion of sap
sections of trunk wood injured in all cases.
and limbs.......... Sept. 14,’12) —-5 . :

Elberta peach twigs Buds 90, 91% dead. Cambium and
(one year old)...... Oct. 5,712) —-5 cortex injured except at base of

one twig. Sap wood injured only
in terminal part twig.

Elberta peach twigs...|Nov. 1,’11) -9 | 104 buds; 63% dead. 33 twigs;
60.6% killed in cambium, other
tissue not injured.

Elberta peach twigs...|Dec. 7,’12] -16 Injury confined to shoulder below
bud and pith region. Buds prop-
er, uninjured.

 

 

 
88

 

 

Tem-
Variety Date pera- Results
ture

Elberta peach twigs...|Mar. 23,'13| -18 | 100 buds, 88% killed. Injury to

wood confined in all cases to sap
wood and pith. |

Rice’s Seedling 138 buds, 44.2 %, killed. Injury to
peach twigs........ Mar. 23,13] -18 wood confined in all cases to sap

wood and pith. Injury less than
to Elberta.

Late Duchess 20 buds, 70% killed. 4 twigs, no

apple twigs.......|July 15,'13| -6 injury. 2

Jonathan apple twigs. |July 16,’13} —5 29 buds, 86.2% killed. 9 twigs, no

injury. :

Jonathan apple twigs..|July 16,’13} —5 24 buds, 58.3% killed. 11 twigs,

no injury.

Young apple twigs, 12 buds, 100% killed. Cortex
variety not given...|July 27,’12) -5 browned in places, especially

around the buds. Cambium dead
in region of annual ring and ter-
minal of year’s growth. Pith dead
in region of annual ring.

Young apple twigs, Leaves practically all injured. Bark
variety not given....|July 27,’12) -5 killed about 7 in. back from ter-

minal. Cambium killed about 7
in. back from terminal. Sap wood
killed 5 to 6 in. back from termin-
al. Pith killed 4 to 5 in. back
from terminal.

Jonathan apple twigs 44 buds, 70% dead. Roots, cam-
and wood from bium and cortex injured through-
three-year old Jon- out. Wood, sections just above
athan tree......... July 28,’13) -5 ground and 3 feet above dead in

cambium and cortex. This year’s
growth injured in cambium and
cortex in older parts, and all tis-
sue dead at tips.

Jonathan apple stems Cortex and cambium injured slight-
from ¥ in. to 1 in. ly in all samples. Sap wood and
in diameter........ Aug. 15,12} -5 pith not injured. No marked

‘ difference between the different
diameters.

Dyehouse cherry
young and old wood|July 28,’13) —5 40 buds, 100% killed. :

Cherry twigs......... Aug. 13,’12} -6 25 out of 36 buds killed. Some

 

 

 

buds at base of new twigs and on
spurs on old wood alive. Leaves
all partially injured; only 25%
entirely killed. Youngest wood
injured worst. Slight injury in
cambium and cortex. No injury
to sap wood oi two year twigs or
older.

 

By referring to this table and to Tables 22, 23 and 24, it will
be seen that the fruit buds are in all seasons apparently less hardy
than any other tissue, except the pith and the tissue at the base of
the buds, and in early winter the wood at the surface of the soil.
89

The most tender tissue of the tree is in the roots. Thus in case
of the tree frozen July 2, 1913 (Table 24) when the tissue above
ground is most tender, the roots were injured in the cambium at -3.5°
C., and severely injured in cambium, cortex and sap wood at -4.5°
C. Goeppert! found that the roots of hardy plants kill at a tem-
perature of from -10° to -15°. A study of the killing temperatures
of roots of various fruit trees has been made at this station. In the
summer there is not so large a difference between the killing tempera-
ture of roots and other tissue. However, the roots do not seem to
develop as great maturity as the tissue above ground. The following
table shows the results with freezing the roots of trees in summer and
winter seasons:

TaBLE 30. SHOWING KILLING TEMPERATURE OF APPLE, PEACH,
PLumM AND PEAR Roots.

 

 

Tem-
Kinds of Roots Date pera- Results
ture
Two-year Ben Davis ‘ Cambium only injured in larger
apple roots..........|June 23,’13] —-5 roots. Cortex also injured in

roots 4 in. in diameter. In 2 out
of 4 cases, crown uninjured. In
other 2 cases there was slight
injury to cambium at crown.
Seedling two-year old
apple stock roots... .|June 24,’13} —5 No injury at all............-..-.-
Two-year Ben Davis No injury in roots above \% in. in
apple roots......... June 25,’13) -3 diameter. Wood just above
crown was injured in cambium.
Seedling apple stock |Aug. 20,12] -6 Cortex and cambium region all

BOOES ercccresscnse: tise asin 80s dead.

Seedling apple stock Cortex and cambium injured, but
POOCS istic 4 eos cere es Aug. 22,’12} -5 less severely than above. .
Two-year Ben Davis Cortex, cambium and wood in-

apple roots......... Dec. 7,712} -6.5 | jured.
Two-year Ben Davis aye
apple roots......... Dec. 7,'12} -4 One small root injured.

Seedling apple stock
roots from basement
since December :

gs: 9 BOLE saga cist cvauenciavaaie Jan. 13,'13] -8 Injury confined to cortex region.

>, Seedling apple stock

-' rootsfrom asement

‘since December Injury slight and confined to cortex

20th sa aise don Jan, 17,13] -9 region.

:. Apple stock buried 5

in. below surface

outside since Jan. One root browned and the other

Sthinnguzsicedees das Mar. 8,'13! -10 not injured...............00006.

 

 

 

1Ueber die Wirmeentwickelung in dem Pflanzen, etc., book, 1830. (Bibl. No. 44).
go

 

 

Tem-
Kinds of Roots Date pera- Results
ture
Apple stock buried 5
in. below surface
outside since Jan.
Stier suns waie die cee Mar. 8,'13} -14 All roots browned...............,

Two year Ben Davis No injury in first 2 inches; cam-

apple roots......... Mar. 24,’13) —10 bium injury throughout remain-
der. Cortex showed next greatest
injury, and in smaller roots sap
wood also injured.

Seedling peach roots...|/June 25,'13) -—3 Entire system injured in cambium
and sap wood. Injury slightly less
in crown.

Seedling peach roots...|June 25,'13] -5 All roots very severely injured in
cambium and cortex and portion of
sap wood. Crown as severely in-
jured as terminal roots. Stem just
above ground injured in cortex
and cambium.

Elberta peach roots.../Oct. 14,'11) -9.5 | 5 roots; 100% dead.

Elberta peach roots...|Oct. 18,’11/ -5.5 | 13 inches of root length; 100%

ead.

Elberta peach roots.../Oct. 19,’11) -4.5 | 3014 inches of root length; 100%
injured, smaller roots injured worst.

Seedling peach roots...|Dec. 7,’12) -6.5 | Cortex, cambium and wood injured.

Seedling peach roots...|Dec. 7,'12] -4 Slight injury.

Marianna plum root...|June 25,13} —-5 Largest root injured severely in
cortex. No apparent difference
between crown and remainder of
root system.

Marianna plum roots. |June 26,13] —3 Crown 1 in. in diameter shows
slight injury in cambium; 3-10
in. down cortex injured also; sap
wood also injured towards tips.

Marianna plum roots..{Dec. 7,'12| —4 Slight injury in cortex.

Marianna plum roots..|Dec. 7,'12| -6.5 Comer cambium and sap wood in-
jured.

Kieffer pear roots..... Oct. 10,'11) -5.5 | 141% inches; 65.5% dead.

Kieffer pear roots..... Oct. 14,’11) -9.5 | 5 roots; 100% dead. Twigs at same
temperature, cambium only killed.

Kieffer pear roots..... Oct. 19,’11) -4.5 | 3314 inches; 100% injured. Kill-
ing more severe in younger roots
some distance from the trunk
than in larger ones.

Kieffer pear roots..... Mar. 27,13] -10 | Injury grading from none in crown

 

 

 

to injury of all tissues where di-
ameter of root was not greater
than 3-10 inch.

 

It will be seen that the killing temperature of the roots varies
from about -3° C. in summer when most tender to about -12° C. in
late winter with rather rapid freezing. The roots are certainly as

: . ‘ ord
hardy in March as in January. Thus they are later in becoming ‘;:
tender in spring than are twigs.

They are still very tender in autumn

1"
a
gi

when tissue above ground has begun to increase rapidly in hardiness.
This may be because the soil is still too cold for growth well up into
March, generally, and continues warm late in autumn.

The following table gives the result of freezing young apple
roots (stock) kept in cold storage at a temperature of 31° to 32° F.,
in the earth frozen up where the temperature varied from the freez-
ing point to 39° F., and others kept in greenhouse conditions whereby
they started into growth, and others kept in basement storage room
at a temperature varying from 4° C. to 15° C. from January 8, 1913
to February 16, 1913, the date of freezing.

TABLE 31. SHOWING RELATIVE RESISTANCE TO Low TEMPERA-
TURES OF APPLE Roots KEPT IN DORMANT CONDITION
AS COMPARED WITH THOSE IN A GROW-
ING CONDITION.

 

 

Kind Tem- | Number Frozen | Basement Cold
of spera- of Greenhouse soil Storage Stor-
Root ture | Roots Room age
Crown cut
diameter
fo in.....| -6 Z No injury..} No injury) No injury} No injury
Second cut
diameter
Yin.....| —6 2 No injury..| No injury| No injury! No injury
Third cut
diameter
din. ....| -6 2 A.Cortex
and cam-
bium
brown.
B.Cambium
brown.....| No injury| No injury) No injury
Fourth cut
diameter All tissues ‘
\ in... ..| -6 2 injured....}| No injury| No injury; No injury
Crown cut
diameter
f in......| -7.5 2 A.Cortex
and
cambium
brown.
B.Cambium
brown..... No injury| No injury| No injury
Second cut
diameter
Yin.....| -7.5 2 A.Cortex
and
cambium
brown.
B.Cambium
brown. No injury] No injury! No injury

 

 

 

 

 

 
92

 

 

 

 

 

 

 

 

 

Kind Tem- | Number Frozen | Basement Cold.
of pera- of Greenhouse soil Storage Stor-
Root ture | Roots Room age
Third cut ‘
diameter .
din.......| -7.5 2 All tissues : en .
injured......| No injury; No injury) No injury
Fourth cut :
diameter ;
Y in......| -7.5 All tissues
injured....| Cambium) Cambium): No injury
brown...) brown.
B. No B. No
injury. injury.
Crown cut
diameter ;
#o in......| -9 All tissues
injured.....| No injury) No injury)|ACambium
injured.
- No
injury.
Second cut
diameter
Yin.....| -9 All injured..;| No injury|ACambium|/ACambium
injured. injured.
BCambium/BCambium
and and
cortex cortex
injured. injured.
Third cut
diameter ‘
Fin......| 9 2 All injured..| Cambium |All injured |All injured
injured.
Fourth cut
diameter ‘
¥ in......| -9 2 All injured. | Cambium
: and All injured] All injured
cortex
injured.
Stored Dec. 20th. The second, third and fourth cuts are sections of the stock

of equal length below the crown.
93

TABLE 31a. SHOWING RELATIVE RESISTANCE TO Low TEMPERA-
TURES OF APPLE Roots KEPT IN DORMANT CONDITION
AS COMPARED WITH THOSE IN A GROWw-
ING CONDITION.

 

. Tem- | Num-
Kind of Root pera- | ber Outside Greenhouse
ture | Roots

 

Crown cut diameter to

VAN sc be Sa thee we BS eed —4 2 No injury....| No injury....
Lower cut diameter \ to
DIN id ob sides eancch asin dy Be so 4 2 No injury....| No injury....
ae cut diameter 4 to
Bs aus noha, Gas Sip alee -6 2 No injury....| No injury....
ower cut to 3 in. in
AiaMeter. iia os cis oc ciw eee cons -6 2 No injury....| No injury....
Crown cut diameter 5, to
MOAN sega tie ee Wes igs etpenseeed -8 2 No injury....| One root very
brown; other
slightly.

Lower cut diameter 4 to

By MDises oe oie 2s mes Somes eee -8 2 | No injury....| Both roots
brown in cor-
tex and cam-

bium.
Crown cut diameter ,3 to
WAR Sci oh, Seu, a iia lara tydee's eden saved -10 2 No injury.....
Lower cut diameter { to
gs Mlnhcs. 6 ieena ae: hau acus Wadia -10 2 One root

brown; other
not injured.

 

 

VAM gs 2g fais ede entiane, Ketererargsee -14 2 All browned...
Lower cut diameter 4 to
ae Wil seta tts fad ede ves Sanees Seve -14 2 All browned...

 

 

 

Stored January 8, 1913,
94

TABLE 31b. SHOWING RELATIVE RESISTANCE TO Low TEMPERA-
TURES OF APPLE Roots KEPT IN DORMANT CONDITION
AS COMPARED WITH THOSE IN A GROW-
ING CONDITION.

 

 

 

 

 

 

Largest Tem-
Where Stored | Diameter] Length | pera- Results,
ture.

Outside....... $3 xa 9+ in...| -9 No injury in first 6 in. from top.
Cambium and cortex slightly
injured in remainder.

Outside....... BAN cass 9+ in...} -9 Cambium injured slightly in last
7 inches.

Outside....... 13 MMs oa oe 8+ in...) -9 Cambium injured slightly in last
7 in; cortex also injured in last
5 in; sap wood injured only at
terminal.

Outside....... 1S Mea aicien 8+ in...| -9 Cambium injured slightly in last
7 in; cortex injured in last 5 in;
sap wood injured at terminal.

a)Cold Storage} .3in...... 7in....| 9 No injury in first 5 in; slight in-
jury in cortex and cambium in
remainder..

Cold storage...| .25in..... 9 in.....| —9 No injury in first 6 inches. Cam-
bium injured in remainder.

Cold Storage.. |} .35in.....| 8in.....| —9 Cambium injury throughout.

Cold storage...! .3in......) 7 in...) —9 Slight injury in cambium through-
out.

b)Greenhouse..| .3 in......]12 in.....| -9 Slight injury in cambium
throughout.

Greenhouse....| .25 in.....]10 in...) —-9 Very slight injury in cambium
in first 5 inches. Cambium and
cortex injury throughout the re-

! mainder.

 

a) In cold storage since January 12, 1913.
b) In greenhouse since January 12, 1913.

TABLE 31c. SHOWING RELATIVE RESISTANCE TO Low TEMPERA-
TURES OF APPLE Roots KEPT IN DORMANT CONDITION
AS COMPARED WITH THOSE IN A GROW-
ING CONDITION.

 

Tem-
Where Stored pera- | Results
ture

 

Greenhouse since March 29, 1913 | -7.5 | Injured in cortex, cambium and sap
; wood throughout.

Cold storage since April 1, 1913..| -7.5 | Cambium injured throughout entire
root. Cortex showed injury only
in the terminal 3 to 5 inches. No
injury in sap wood.

Basement store room since De-

cember, 1912................. ~-7.5 Slight injury.
95

It will be seen that there is little difference between the killing
temperature of those in storage and those in a storage room at 10 to
37° F. higher temperature and those kept out in the soil. However,
those that were in a growing condition were less hardy but with
nothing like the difference that would be observed in the case of twigs
kept under similar conditions. The reason the roots kept in the
basement store room were more hardy than we should expect, is
possibly because of their being kept in a somewhat dry condition.

In the case of young peach roots, those kept in cold storage
showed a greater hardiness than those kept in the soil outside. Some
growth may have taken place in the roots kept out in the soil. The
following table gives results of the freezing of peach roots:

TaBLE 32. SHOWING RELATIVE RESISTANCE TO Low TEMPERA-
TURE OF YEAR-OLD SEEDLING PEACH Roots GROWING AND IN A
THOROUGHLY DORMANT CONDITION.

DaTE OF FREEZING, Marcu 22, 1913.

 

Location Tem-
Where Stored 0 Diameter | Length | pera- Results
Root ture

 

Outside since
January 12,
1913........| Top even with

surface...... .65in.....| 14 in...) 9 No injury in
first 2 in. be-
low the surface
of the soil. Cor-
tex, cambium
injured in next

4 in. All tis-
Outside since sues injured
January 12, in remainder.
1993 vss ciace vs 2 inches below
low surface....|) .35 in.....| 12 in....| —9 Cambium and
cortex injured
throughout.
Sap wood
Outside since slightly injured
January 12, ‘ in last 3 in.
LS sce sedate 4 inches be-
low surface....) .3in...../ 12 in...) -9 Cortex and cam-

bium injured
severely
throughout.
Sap wood and
pith;in last 8
inches.

 

 

 

 

 
96

 

 

Location Tem-
Where Stored of Diameter | Length | pera- Results
Root ture
Outside since
{eauary 12,
1913s aiecgeses 6 inches be- .
low surface....| .3 in....../ 10in...] -9 Cambium and
cortex injured
throughout.
Sap wood and
Cold storage... pith in last 6
since January inches.
12, 1913......| Top even with :
surface...... -7in....| ILin...| -9 Very slight in-
jury of cam."
bium through:
out. Cortex’,
Cold Storage slightly in last
since January 2 inches,
12, 1913.. ...| 2 inches below
‘surface...... -3in....} Q9in...| -9 | Very slight in-
jury of cam-
bium through-.
out. Cortex in-
Cold storage... jured in last
since January 3 in.
12, 1913...... 4 inches be-
low surface...) .35in.....} 8in...} -9 Cambium and
cortex injured
throughout.
Cold storage... Pithi cane se
since Januar 3 inches...
12, 1913.....] 6 inches be-
low surface....) .3in.....) O6Oin...| —9 Cambium and
cortex slightly
injured
throughout.
(Injury in all
cases very
much less than
Greenhouse in those kept
since January outside),
12, 1913.... Top even with
surface...... -7in...../ 11in...{ -9 | Very severe in-
jury through-
out in cam-
bium and cor-
tex. Pith and
Greenhouse wood less se-
since january verely injured.
12, 1913.. 3 inches below
surface...... -55 in... .| 15 in...) 9 Very severe in-
Greenhouse jury in all tissues
since January
12, 1913..... 3 inches below
surface...... Sin... -9 | Very severe in-

 

 

 

 

 

jury in all tis-
sues.

 

 
97

The following table gives the results of freezing Marianna plum
roots:

TABLE 33. SHOWING RELATIVE RESISTANCE TO LOW TEMPERA-
TURE OF YEAR-OLD SEEDLING PLUM Roots Grow-
ING AND IN A THOROUGHLY DORMANT
CONDITION.
DaTE OF FREEZING, Marca 22, 1913.

 

 

 

 

 

 

 

- Location Tem-
Where Stored oO Diameter | Length | pera- Results
Root ture
Outside........ Top even with
surface...... -8in.....| 16 in...) -9 Very slight in-
jury of cam-
bium in first 10
in. Cortex and
cambium _in-
jured in re-
mainder.
Outside........ 3.5 inches be-
low surface... 3 in 12 in....| -9 Cambium and
cortex injury
throughout.
Outside........ 4 inches below
surface...... -3in....| 14 in...) -9 Cambium and
cortex injury
throughout.
Outside........ 4 inches below
surface...... .25in.....| Oin...| 9 Cambium and
: cortex injury
throughout.
Pith injured
slightly in last
4 inches.
Cold storage. ..| Top even with ; :
surface...... .8in. ..} 9in....| -9 | Very slight in-
jury in cambi-
\ um in first 7 in.
Cortex and
cambium _in-
jury in remain-
der.
Cold Storage...| 7 inches below . 2
surface...... .35in....J 8 in. -9 Slight injury of
cambium and
cortex through-
out.
Cold storage. ..| 7 inches below :

j i surface...... .35in....| 7in...| -9 | Slight injury of
cambium and
cortex through-
out.

Greenhouse....| Top even with ; 2
surface...... 7 im... 7in....| —9 Very severe in-
jury of cortex
and cambium
throughout.
Pith and sap
wood injured.
98

 

 

Location Tem- 4
Where stored of Diameter | Length | pera- Results:
Root ture
Greenhouse....} 7 inches below
surface...... -45in.....| 10in...| -9 Very severe in-
jury of cortex
and cambium
throughout.
Pith and sap
wood injury.
Greenhouse....| 7 inches below
surface...... -35in....| 3in...}| -9 | Very severe in-
jury of all tis-
sue,

 

 

 

 

 

 

In the root system of trees growing out of doors there is great
difference in the relative hardiness. The crown of the tree—that is,
the part of the root just beneath the ground—will withstand con-
siderably lower temperatures than parts of the root lower down, and
the small ends of the roots kill more easily than the larger parts.
In fact as the roots extend away from the crown they become more
and more tender and apparently this tenderness is greater on those
roots that extend downward into the soil. Goff thinks that in’
Wisconsin the ends of the roots may be killed during every winter.
The following table presents data covering this point. The Angers
quince roots were frozen on January 25, 1913; the seedling peach
roots on March 22, 1913 and the balance on March 24, 1913. See
also Table 36 for the same kind of data on plum and cherry roots.

TABLE 34. SHOWING RELATIVE HARDINESS OF VARIOUS PARTS OF
THE Root System oF Fruit TREEs.

 

 

Location ‘Largest Tem-

Kind of Root oO! Diameter | Length | pera- Results
Root ture
Two-year
Kieffer pear
on Japan
stock........ Top even with
surface...... lin.......] 16 in...) -10 | No injury in

first inch. Cam-
bium injury
throughout,
remainder.Cor*;
tex injury last
13 inches. Sap
wood in last 9
in,

 

 

 

 

 
99

 

 

Location Largest Tem-
Kind of Root of Diameter | Length | pera- Results
Root ture
Two-year
Kieffer pear
on Japan i
stock........ 4 inches below
surface...... .5in.....| 12in....| -10 | Cambium and
cortex injury
throughout.
Sap wood in-
Two-year jury in last 8
Kieffer pear inches.
on Japan
stock........ 4 inches below
surface...... .45 in....| 10 in....| -10 Cambium, cor-
tex and sap
Two-year wood injured.
Kieffer pear throughout.
on Japan
stocks icccses 4 inches below
surface...... 3 in. 6 in....| -10 Cortex and cam-
bium injured
severely
throughout;
sap wood in
. last 5 inches.
Kieffer pear
roots>....... Top even with
surface...... 1.2 in....| 15 in....| -10 No injury in
first 8 inches;
slight injury
in cortex and
cambium in re-
mainder.
Kieffer pear
roots........ 4.5 in below
surface...... 6 in 12 in....} -10 | No injury in
first 2 inches;
cambium and
cortex injury
in remainder;
. pith injury in
last 5 inches.
Kieffer pear
roots........ 6 inches below
surface...... .4in....| 12 in....| -10 No injury in
first 3 inches;
cambium and
cortex and sap
wood injury in
Kieffer pear remainder.
roots........ .3 inches be-
low surface... .3in....{ 8 in....| -10 Cambium and
cortex injury
throughout.

 

 

 

 

 

Sap wood in-
jury in last 4
inches..
Ioo

 

 

Location Largest Tem-
Kind of Root oO Diameter | Length | pera- Results
Root ture
Two-year Ben
Davis apple
roots........ Top even with
surface...... -8in....| 12 in...) -10 | No injury in
first 2 in. from
top. Cambium
injury in re-
mainder. Cor-
Two-year Ben tex injury in
Davis apple last 3 inches.
roots........ 6 inches below
surface...... .25 in...| 10 in...) -10 | Slight injury in
cambium
throughout.
Two-year Ben Cortex injury
Davis apple in last 2 inches.
roots........ 6 inches below
surface...... .25 in...| 8in...| -10 | Cortex and
cambium in-
jury through-
out. Pith in-
Two-year Ben jury in last 5
Davis apple inches.
roots........ 6 inches below
surface...... -2in....| 6in....| -10 | All tissues in-
jured through-
Two-year Ben out.
Davis apple °
roots....,...| 6inches below
surface...... .2in....| 12 in...) -10 | Cortex andcam-
bium = injury |
throughout, °
Sap wood in-
Two-year Ben jury in last 6
Davis apple inches.
roots........ Top even with
surface...... -8in....} 14 in...) -10 | Cambium _ in-
jury through
out. Cortex
injury in last 6
in; sap woo
Two-year Ben in last 5 inches.
Davis apple
roots........ 5 inches below
surface...... 25 in...| 8in....| -10 | Very slight in-
jury in cortex
and cambium
Two-year Ben in last 2 inches.
Davis Apple ;
roots........ 9 inches below
surface...... -35in...} 8 in....| -10 Cortex and cam

 

 

 

 

 

bium _ injury
throughout
Sap wood in-
juryBin last
inches.
IoI

 

 

 

 

 

 

 

Location Largest Tem-
Kind of Root oO Diameter | Length | pera- Results
Root ture
Two-year Ben
Davis apple
roots........ 11 inches be-
low surface... 3 in. 6 in....| -10 Cortex and cam-
bium injury
throughout.
No injury in
One-year sap wood.
French apple
seedlings..... -4in....) 12 in....| -10 Cambium _in-
jury in last 11
in; cortex in-
jury in last 6
in; pith injury
One-year in last 2 inches.
French apple
seedlings..... -4in....] 11 in....} -10 Cambium in-
jury through-
out; cortex in-
jury in last 10
in; sap wood
injury in last 4
One-year inches.
French apple
seedlings..... -35in...| 8in....| -10 | Cambium slight-
ly injured
throughout;
cortex injury
One-year in last 3 inches.
Japan pear
seedlings. .... ‘ 4in 11 in....| -10 Cambium in-
jury through-
out; cortex in-
jury in last 7
inches sap
wood injury
-One-year in last 3 inches.
Japan pear : ‘
seedlings..... .4in....]10.5 in...) -10 | Cambium — in-
jury through-
out; cortex in-
jury in last 8
inches; sap
wood injury in
One-year last 2 inches.
Japan pear 3 : : ‘
seedlings. ..... .35in...| 9in....| -10 | Cambium  in-
jury through-
out; cortex in-
jury in last 7
inches; sap
wood injury in
last 4 inches.
Angers Quince .
roots........ .Sin.... -7 Cortex slightly

injured.
102

 

 

Location Largest Tem-
Kind of Root of Diameter | Length | pera- Results
Root ture
Angers Quince
roots........ . 25 in... ~7 Cortex injured,
Angers Quince
roots........ .18 in... -7 Cortex and cam-
bium injured.
Angers Quince
roots........ .12 in... -7 Cortex and cam-
bium injured.
Angers Quince
roots........ Sin... -9 Cortex injured,
Angers Quince
roots........ 25 in... -9 Cortex injured,
Angers Quince
POOC Sc xine iene 18 in... -9 Cortex and cam-
bium injured.
Angers Quince
roots........ . 12 in... -9 Cortex and cam-
bium injured.
Seedling Peach
roots........ Top even with
surface...... -65 in...| 14 in....| -9 No injury in
first 2 inches
from top; cor-
tex and cam-
bium _ slightly
injured in next
4 in; all tissues
injured in re-
Seedling Peach mainder,
roots........ 2 inches below
surface...... -35 in...| 12 in...) -9 Cambium and
cortex injury
throughout.
Sap wood.
slightly injured,
in last 3 inches, |
Injury very
slight nearest
Seedling Peach crown.
roots........ 4 inches below
surface...... -3 in....| 12 in....| -9 Cambium and
cortex injured
severely
throughout.
Sap wood and
pith injury in
Seedling Peach last 8 in.
roots........ 6 inches below
surface...... 3 in....| 10 in....| -9 Cambium and
: cortex injury
throughout. -

 

 

 

 

 

Sap wood and
pith injury in
last 6 inches. “y

 

Four-year old Elberta peach roots subjected on October 19, 1911, to a
temperature of -4° C., showed both live and dead tissue intermingled. The
younger roots lying some distance from the trunk of the tree showed the tissue
to be all dead, killing worse than the larger roots near the trunk.
103

These roots were in all cases kept during the time preceding
the freezing in such a position that all parts must have been exposed
to practically the same temperature, so it is not possible that the
diminished hardiness of the parts furthest from the crown could
have been caused by their being exposed to a higher temperature
during the period preceding the freezing. It probably represents
the most rapidly growing tissue, but dt times of freezing the tissue
had not been growing for at least three months. It also represents
tissue that under normal conditions is not so liable to be exposed
to low temperatures so in the evolution of the plant it would not be
so necessary for it to develop hardiness.

Of great interest, practically, is the hardiness of various stocks
of fruit trees. Through the courtesy of Mr. E. S. Welch of Shenan-
doah, Iowa, this station was able to study various stocks. In the
case of apple trees worked on French crabs, a considerable number
of trees were furnished that had rooted from the scions, as well as
from the stock, thus permitting a comparison between these scion
roots and the roots from the stock. The trees were received Decem-
ber 20, 1912 and were heeled-in inthe shade. The roots were thus at
a temperature near the freezing point from the time they were re-
ceived until they were frozen. The following table gives the results:
104

TABLE 35. SHOWING RELATIVE HARDINESS OF STOCK AND SCION
Roots.

 

Date Tem-
of pera- Material and Results

Freezing | ture

 

Two-year old Ben Davis apple trees.

Feb. 18,'13] -11 Scion root diameter }; in. uninjured for first 6 inches,
Cortex and cambium injury in remainder.

Feb. 18,'13] -11 Similar root from stock dia. ;4 in.,- uninjured for first 7
inches. Cortex and cambium injury in remainder.
Feb. 20,'13) -15 | A. Scion root, largest dia. 3g in., length 14 in. No injury
whatever. ,

Feb. 20,13} -15 B. Scion root, coming from scion 2 inches below A. Largest
dia* 4g in; length 12 in. No injury in first 5 inches; last
7 inches were slightly browned. :

Feb. 20,'13} -15 C. Scion root, 2 inches lower than B. Largest dia. J,
in; length 12 in. No injury in first 6 inches; slight injury
in last 6 inches.

Feb. 20,'13| -15 D. Stock root, 1 inch below C. Largest dia. 3g in; length
10 in. Severe injury throughout.

Feb. 20,'13) -15 E. Stock root, 2 inches below D. Largest dia. 14 in; length
10 in. Very severely injured throughout.

Feb. 20,’13} -15 F. Stock root, 4 inch below E. Largest dia. 3g in; length
12 inches. Severe injury throughout.

Feb. 20,13] -15 G. and H. Arise at same point as F. Each ) in. in dia.
at largest point; both 12 in. long. Severe injury in both.
Feb. 20,'13) -15 Main root. Largest dia. 8g in. No injury to scion part.
Injury to cortex in stock part.

Feb. 20,’13} -15 | Fibrous roots under ;4 in. dia. Injury on those from
stock and not on those from scion.

Mar. 3,13} -15 A. Scion root 4 inches below ground. Largest dia. % in;
length 10 in. No injury in first 5 inches. Remainder
very slightly browned.

Mar. 3,13} -15 B. Stock root attached 2 inches below A. Largest dia. 4
in; length 14 in. Injury throughout entire length.

Mar. 3,13] -15 C. Stock root 2 inches below B. Largest dia. \% in; length
10.in . Injury in first 4 inches slight; remainder well
browned.

Mar. 3,’13) -15 D. Stock root same size as C. Attached at same portion
of main root. Injury somewhat more severe than C.
Mar. 3,’13] -15 Main root. Scion part, dia. 34 in., shows no browning.
Stock part, dia. 14 in. is slightly browned.

Two-year old Wealthy apple trees

Mar. 3,13} -15 A. Scion root. Largest dia. 4% in; length 12 in. No injury
in first 7 inches; remainder slightly injured.

Mar. 3,13; -15 | B. Continuation of main root. Largest dia. 3-8 in; length
8 oe No injury in first 3 inches; last 5 inches slightly in-
jured,

Mar. 3,13) -15 C. Stock root. Largest dia. 4% in; length 12 in. Arises
nearly opposite Root A. No injury in first 6 inches; re-
Pegs slightly injured. No marked difference between

and B.

 

 
105

In most cases those roots that came from scions were more hardy
than those of the same size coming from the stock, indicating that
the French seedling roots are less hardy than roots of a variety like
Ben Davis. This station has been unable to compare the hardiness
of scion roots from hardy varieties like Fameuse with those from
very tender varieties like Jonathan.

A comparison similar to the foregoing was made with different
stock of plums and cherries using the Myrobolan and Marianna
varieties of plums and Mazzard and Mahaleb varieties of cherries.
The following table gives the results:

TABLE 36. SHOWING RELATIVE HARDINESS OF MAZZARD AND Ma-
HALEB CHERRY STOCK AND MARIANNA AND
MyYrospoLan Pium STOCK.

Date of Freezing, January 25, 1913.

 

 

 

 

 

 

 

Location Largest Tem-
Kind of Root ° Diameter | Length | pera- Results
Root ture
Mazzard : ote
cherry roots.. VY in... -7 No injury.
Mazzard : _.
cherry roots.. Yin... -7 No injury.
Mazzard ; 3
cherry roots.. fe AMlvescee -7 No injury.
Mazzard : aoe :
cherry roots.. Min... -7 Slight injury in
cortex.
Mazzard ; a
cherry roots... Yin... -9 No injury.
Mazzard . —_
cherry roots. . Yin... -9 No injury.
Mazzard : :
cherry roots. . fe INS S540 -9 Slight browning
in cortex.
Mazzard
cherry roots.. Min... -9 Cortex and cam-
bium injured.
Mahaleb . oe
cherry roots. . Ww in...... -7 No injury.
Mahaleb . _
cherry roots.. Yin...... -7 No injury.
Mahaleb hoot
cherry roots.. fs im... oe -7 Cortex injured.
Mahaleb ‘ aos
cherry roots.. Min... -7 Cortex injured.
Mahaleb ne
cherry roots.. Ww in...... ~9 Cortex injured.
Mahaleb :
cherry roots.. Yin... -9 Cortex and cam-
bium injured.
Mahaleb
cherry roots.. fs im...... -9 Cortex and cam-
bium injured.
Mahaleb
cherry roots.. ¥in...... -9 Cortex and cam-
bium injured.
106

Date of Freezing, March 18, 1913.

 

 

 

 

Location Largest Tem-
Kind of Root o Diameter | Length | pera- Results
Root ture
Mazzard
cherry roots..| 3 inches below
surface...... 1.1in....| 7 in....] -10 Cambium and
cortex injured
throughout.
Least severe
Mazzard near crown.
cherry roots..| 3.5 inches be-
low surface.. .' .3in...| 5Sin...| -10 Cambium and
cortex injured
throughout.
Least severe
Mazzard near crown.
cherry roots..| 4 inches below
surface...... .3in...| 7 in....| -10 Cambium and
cortex injured
throughout.
More _ severe
Mazzard than above.
cherry roots..| 4.5 inches be-
low surface.... -3in....| 12 in....]| -10 Cambium and
cortex injured
severely
Mazzard throughout
cherry roots..| 5 inches below
surface...... «45 in...| 6 in....| -10 Very severe in-
iury in cam-
bium and cor-
tex through-
Mazzard out.
cherry roots..| 5.5 inches be-
low surface.... -A4in....| 10 in....| -10 Very severe in-
jury in cam-
bium and cor-
tex through-
out.
Mazzard
cherry roots..| 534 inches be-
low surface.... .28 in...) 28 in....| -10 Cortex and
cambium  in-
jured severely.
Fick injured
slightly. :
Mazzard aie
cherry roots..| 614 in. below
surface...... -15 in...) 8in....| -10 | All regions in-
jured.
Mazzard
cherry roots..| 634 inches be- .
low surface....} 2in......] 6in....| -10 | All regions in-
jured.
Mazzard
cherry roots..| 9144 in. below a
surface.......] Lin..... -10 All regions in-
jured.

 

 

 
107

 

 

Location Largest Tem-
Kind of Root oO! Diameter | Length | pera- Results
Root ture
Mazzard
cherry roots..| 2 inches below
surface.......] lin......] 8 in....] -10 Cortex and cam-
bium injury
throughout.
Least injury
near crown.
Pith killed last
Mazzard 5 inches.
cherry roots..| 3 inches below
surface...... .3in....| 6 in....| -10 All tissues se-
Mazzard verely injured.
cherry roots..| 4 inches below
surface...... .3 in....] 10 in....| -10 Cambium and
cortex injured
severely first 3
inches of root.
All tissues
injured in re-
Mazzard - mainder.
cherry roots..| 4 inches below
surface...... .5in....| 10 in...) -10 Cambium and
cortex injury
throughout.
Pith injury last
Mazzard 5 inches,
cherry roots..| 434 inches be-
low surface... .45 in...| 14 in....| -10 | Cambium and
cortex injured
very severely
throughout.
Pith injured in
Mazzard last 12 inches.
cherry roots..| 634 inches be-
low surface.... .4in....]| 8 in....} -10 Cambium and
cortex injured
very severely
throughout.
Pith injured in
Mazzard last 3 inches.
cherry roots..| 714 inches be- ; :
low surface. . .2in....| 6in...| -10 All tissues in-
jured through-
Mazzard out.
cherry roots..| 9 inches below ; . :
surface...... .15in...] 6in..,.| -10 All tissues in-
" jured through-
Mizesed ioectndies out.
cherry roots.. inches be-
j jaw surface... .2in....! 4-6 in...) -10 |! All tissues very
severely in-
rs ase jured.
ots..| 6 inches below
ae surface...... .15in...| 3in....] -10 | All tissues very

 

 

 

 

 

severely in-

jured,
108

 

 

4
Location Largest Tem-
Kind of Root of Diameter | Length | pera- Results
Root ture
Mahaleb
cherry roots..} 2 inches below
surface.......| Lin.....) 13 in....} -10 | No injury in
first 6 in. Very
slight injury
in cambium in
next 3 in. Cam-
bium and cor-
tex injury in
Mahaleb remainder.
cherry roots..| 8 inches below
surface...... .2in....| 4in....] -10 | Cambium and
cortex injury
Mahaleb throughout.
cherry roots..| 10 inches be-
low surface... .35 in,..| 4 in....| -10 Cambium and
cortex very
i slightly in-
jured.
Mahaleb
cherry roots..| 6 inches below
surface...... -lin....| 4in....] -10 | Cambium and
cortex injured
Mahaleb severely,
cherry roots..| 2 inches below
surface....| 1in......} 14 in...) -10 | No injury in
: first 4 inches,
Cambium and ,
cortex injured .
very _ slightly
throughout
Mahaleb _ remainder.
cherry roots..| 6 inches below
surface...... -4in....| 6in...| -10 | Cambium -and
cortex injury
throughout.
Mahaleb
cherry roots..| 10 inches be-
low surface.... .35 in...} 2 in....| -10 Slight injury in
cambium and
cortex.
Mahaleb
cherry roots..| 914 inches be-
low surface... -2in....| 3in...| -10 | Cambium and
cortex injured.
Date of Flreezing, Ma|rch 21, 1/913.
Mazzard
cherry roots..| At surface....] 1.1in....} 11 in..../ -10 Cambium in-
jured through-
out. Cortex.in
jury in last 8
in. More severe
near terminal,
least injury
near crown.

 

 

 

 

 
109

 

Kind of Root

Location

oO
Root

Largest
Diameter

Length

Tem-
pera-
ture

Results

 

Mazzard
cherry roots..

Mazzard
cherry roots..

Mazzard
cherry roots..

Mazzard

cherry roots. .

Mazzard
cherry roots..

Mazzard

cherry roots..

Mazzard
cherry roots..

Mazzard
cherry roots. .

Mazzard
cherry roots. .

 

3 inches below
surface......

3 inches below
surface......

3% inches be-
low surface...

5 inches below

surface......

10 inches be-
low surface....

At surface....

2 inches below
surface......

2 inches below
surface.......

2% inches be-
low surface...

 

45 in...

.3 in...

.3 in...

1.1 in...

.5 in...

.45 in...

5 in...

 

8 in...

4 in...

6 in....

10 in...

13 in...

10 in....

8 in....

5 in...

 

-10

 

Cambium in-

jured through-
out. Cortex in-
jured in last 5
in. Least in-
jury nearest
crown.

Cambiumslight-
ly injured
throughout.

Cambium and
cortex injury
very slight.

Cambium and
cortex injured
throughout.
Pith injured in
last 3 inches.

Cambium and
cortex severely
injured
throughout.
Pith injured
less severely.

Cambium in-
jury through-
out. Cortex
and cambium
in last 8 in.
Cortex, cam-
bium and pith
in last 5 inches.

Cambium in-
jury through-
out. Cortex
and cambium
in last 8 in.
Cortex, cam-
bium and pith
in last 5
inches.

Cortex and cam-
bium _ injury
throughout.

Cortex and cam-
bium injury
throughout.
Ito

 

Kind of Root

Location

oO
Root

Largest
Diameter

Length

Tem-
pera-
ture

Results

 

Mazzard

cherry roots..

Mazzard

cherry roots..

Mahaleb

cherry roots..

Mahaleb

cherry roots..

Mahaleb

cherry roots.,

Mahaleb

cherry roots..

Mahaleb

cherry roots...

Mahaleb

cherry roots..

 

3 inches below
surface......

7 inches below
surface......

Date of F

1 inch below
surface....

2 inches below
surface......

3 inches below
surface......

4 inches below
surface......

5 inches below
surface ee

1 inch below
surface......

 

.3 in...

.25 in...
reezing, M

VAT sass

.15 in...

-4 in...

-4in....

.3 in...

lin...

5 in...

5 in...
arch 21,1

10 in...

6 in...

8 in....

6 in....

4 in...

| 14 in...

 

-10

~10

913.

-10

 

 

Cortex and cam-
bium severely
injured
throughout.
Pith injury in
last 4 in.

Cortex and cam-
bium injury
throughout.
Pith injury in
last 3 inches.

No injury in 5
in. nearest -
crown. Cortex
injury _ slight
in remainder.

Cambiumslight-
ly injured in
first 2 in. Cam-
bium and cor-
tex in remain-
der.

Cambium and-
cortex injury
throughout.
Very slight
nearest crown.
Pith injury in
last 2 inches.

Cambium and
cortex injury
slight in first 2
in.; more severe
in next 2 in.
Cambium, cor-
tex and pith in-
jury in termi-
nal 2 inches.

Cambium and
cortex slightly
injured.

No injury in

highest in
Very slight
injury in cam-
bium and cor-
tex of remain-
der.
 

 

 

 

 

 

 

 

Location Largest Tem-
Kind of Root oO Diameter | Length | ’pera- Results
Root ture
Mahaleb
cherry roots..| 4 inches below
surface...... -3in...{ 8in...]| -10 | No injury in
first 4in.; slight
injury in cam-
bium and cor-
tex in remain-
Mahaleb der.
cherry roots..| 4 inches’below
surface...... -45in...}| 10 in...) -10 | No injury in
first 3 inches;
cambium and
cortex injury
in remainder;
! injury becom-
é ing more severe
Mahaleb near terminal.
cherry roots..| 4 inches below
surface...... -5in....| 5in...| -10 | No injury first
inch. Cambium
and cortex in-
jured in re-
Mahaleb mainder.
cherry roots..} 7 inches below
surface...... .3in....| 3 in....} -10 Slight injury in
cambium and
cortex.
Date of Flreezing, Mlarch 18, 1/913.
Myrobolan
plum roots....| 2 inches below
surface...... .8in....| 7.5 in| -10 | Cortex injured
first 5 in.; cor-
tex and cam-
bium injured
. Myrobolan next 2 4 inches.
plum roots...| 3 inches below
surface...... -4in,...| 9.5 in.| -10 Cortex and cam-
bium injured in
all. Pith in-
jured in last
Myrobolan 5% inches.
plum roots...| 6 inches below ‘
surface...... 2 in 6 in -10 All regions in-
jured, less se-
vere near point
Myrobolan of attachment.
plum roots...| 9 inches below ;
surface...... .3in....| 3in...| -10 | AIl regions in-
jured, less sé-
verely near
; point of at-
». Myrobolan tachment.
plum roots...| 12 inches be- :
' low surface. . .25in...] 3in...| -10 | All regions very
, severely in

jured.
II2

 

 

Location Largest Tem-
Kind of Root of Diameter | Length | pera- Results
\ Root ture
Myrobolan
plum roots...| 14 inches be-
low surface....,) 1in.....| 6in....} -10 | All regions very
severely in -
Myrobolan jured.
plum roots...| 2 inches below
surface...... .7in....| 12 in...) -10 | Cortex injured
: slightly in first
3in.;cortexand |.
cambium in- |”
jured slightly
next 6 in.; pith ©“
injured slightly
and cortex and
cambium se-
verely in last 3
Myrobolan inches.
plum roots...| 234 inches be-
low surface... -3in...| 6in...| -10 Cortex injury in
' first inch. Cor-
tex and cam-
bium injury in
remainder,
severe near ter-
Myrobolan minal.
plum roots...] 334 inches be-
low surface... .2in...| Sin... |.-10 | All tissues in-
jured. Injury
most severe -
Myrobolan near terminal,
plum roots...| 414 inches be-
low surface.... -3in....] 10in...} -10 | All tissues in-
jured. Injury
most severe
Myrobolan near terminal.
plum roots...| 434 inches be-
low surface.... .2in....| 9 in....| -10 Same as above.
Myrobolan
plum roots...| 11 inches be-
low surface... -35 in...] 3 in....| -10 Same as above.
Myrobolan
plum roots...| 11 inches be-
low surface -15 in...) 3 in....| -10 | Same as above.
2 Date of Fjreezing, Miarch 20, 1/913.
Marianna
plum roots...| 7 inches below
: surface...... Lin.....) 2 in....| -10 No injury no-
Marianna ticeable.
plum roots...| 9 inches below
surface...... -6in....| 12in....] -10 | Slight injury to

 

 

 

 

 

cambium = in
first 6 inches;
all tissue in-
jured in re-
mainder.

 
113

 

 

 

 

 

 

 

: Location Largest Tem-
Kind of Root of Diameter | Length | pera- Results
Root ture
Marianna
plum roots...| 9 inches below
surface...... .55 in...] 6 in....| -10 Cambium in -
jured first 3
inches. Ca m-
bium and cor-
tex in remain-
Marianna * der.
plum roots...| 9 inches below
surface...... .5in....] 12n....] -10 Cambium in -
jured first 3
inches. Cortex
and cambium
next 2 inches;
- cortex, cam-
bium and pith
Marianna in remainder.
plum roots...| 9 inches below
surface...... .5in,...| 5 in....| -10 Cambium and
cortex injured
very slightly
Marianna throughout.
plum roots...| 9 inches below
surface...... .45 in...| 10 in....] -10 All tissues in-
Marianna ‘jured.
plum roots...| 12 inches be-
low surface.... .2in....| 6 in....| -10 All tissues in-
Marianna jured.
plum roots...| 9 inches below .4in....) 10 in...) -10
surface....... All tissues in-
jured.
Date of Fjreezing, Mijarch 24, 1/913.
Marianna
plum roots...} 1 inch below |
surface...... 1 in..,...] 14 in....] -10 No* injury to
first 5 inches;
slight injury
to  cambium
next 3 inches;
slight injury to
P cortex in = re-
‘Marianna mainder.
plum roots...} 2 inches below
surface...... .4in 8 in....| -10 Slight injury in
cortex and and
cambium
throughout.
More _ severe
Marianna towards tip.
plum roots...| 244 inches be-
low surface... 3 in 10 in....] —10 Same as above.
Marianna
plum roots...| 2 inches below
surface...... .2in....| 8 in -10 Same as above.
» Marianna
plum roots....| 6 inches below .
surface...... .35 in...) 14 in....} -10 Cambium = and
cortex injured
throughout.
More _ severe
last 8 in. Pith
last 4 in.
114

 

 

Location Largest Tem-
Kind of Root of Diameter | Length | pera- Results
Root ture
Marianna
plum roots....| 614 inches be-
low surface.... .15in...| Oin....} -10 Cambium and
cortex injured
Marianna throughout.
plum roots...| 844 inches be-
low surface.... .15 in...| 4 in...) -10 Cambium and
cortex injured
Marianna throughout:
plum roots...| 1014 inches be- ‘
low surface.... .45 in...| 3 in...} -10 Cambium and
‘ cortex slightly
Myrobolan injured,
plum roots...} 1 inch below
surface...... 8 in.. 12 in...) -10 Cortex, cam-
bium and pith
injured slightly
throughout.
More _ severe
further from
Myrobolan crown.
plum roots...| 3 inches below
surface...... .3 in....}| 10 in....] -10 Cambium and
cortex injured
severely
throughout;
pith injured
Myrobolan slightly.
plum roots...| 41% inches be-
low surface... .3in....| 8 in....] -10 | Same as above.
Myrobolan .
plum roots...| 5 inches below
surface...... .25 in...| Q9in...]| -10 | All tissues se-
verely injured.
Myrobolan :
plum roots...| At surface.... -8in....| 10 in...) -10 Cambium, cor-
tex and pith in-
jured in all.
More severely
Myrobolan near tip.
plum roots...} 3 inches below
surface...... -35 in...] Sin...| -10 | ‘Cambium and
cortex severe-
ly injured
throughout.
’ Pith injured in
Myrobolan : last 5 inches.
plum roots...| 5 inches below
surface....... .2in...| 4in...{ -10 | Cambium and
cortex severe-
ly injure
throughout. .,
Pith injured
Myrobolan slightly.
plum roots.,.| 7 inches below
surface...... .2in...| 4in....| -10 | All tissues se-

 

 

 

 

 

verely injured.

 
115

Freezing to Death of Pollen. The killing of the bloom and
young fruit of the peach, apple and some other fruits will be dis-
cussed later in this paper. However, it is perhaps not out of place
to discuss here the killing of pollen. Schaffnit! exposed the pollen
of a number of species of plants to a temperature of -17° C. for eight
hours with no apparent harmful effects, while Sandsten? apparently
reduced the germination percentage of pear, plum, cherry and peach
pollen by exposing for six hours to a temperature of 1.5°. At this
station pollen of the Jonathan and Cillago apples was frozen with
the result shown in Table 37. The pollen was frozen for eighteen
hours and then germinated in a 10% sugar solution.

TABLE 37. SHOWING EFFECT OF Low TEMPERATURE ON GERMINAT-
ING POWER OF POLLEN GRAINS.

 

 

 

Tem- Time Percentage | Percentage
Kind of Pollen Date pera- at Germination, Germination
ture | Minimum |] Unfrozen Frozen
Jonathan apple.......|Apr. 24,’13} -3 45 min.... 84.0 33.0
Jonathan apple.......
pollen dried....... May 29,'13} -13 60 min.... 25.0 20.0
(estimate) | (estimate)
Cillago apple.........]May 10,’13| -8 30 min.... 66. 25.0
Cillago apple.........|May 10,’13) -12.5) 30-min.... 66.66 00.0

 

 

Thus the pollen will still germinate after exposure to as low
_ temperature as -8° C., and dried pollen at as low a temperature as
-13, a much lower temperature than the other flower parts will with-
stand.

Discussion of the killing temperature of other flower tissues
will be found in a later part of this paper.

Rest Period of Plants. Closely associated with the question
of maturity in the fall is that of maintaining a condition of maturity
in late winter. Plants that have started into growth in spring soon
reach a condition whereby they are as tender as they were in early
fall, and sometimes even more so. Under conditions such as prevail
in the southern half of Missouri, where growth may continue late in
autumn, and where in January and early February, there are likely
to be days warm enough for considerable growth to take place, it has

1Mitt. Kaiser Wilhelm Inst. Landw. Bromberg. Vol. 3, No. 2, pp. 93-115, 1910. (Bibl.
No. 98).
7Wis. Agr. Exp. Sta. Research Bul. 4, pp 163-5. (Bibl. No. 97).
116

been found that with the peach, the winter rest period of the fruit
buds is an important factor in influencing the amount of killing from
cold. By the rest period is meant the period during which the buds
will not respond in growth to favorable temperature conditions with-
out special treatment. This rest period is shorter with some varie.
ties than with others, and with all varieties tried at this station the
rest period is prolonged later into the winter if the tree makes a vig-
orous growth and continues growing rather late in the season. They
will not, therefore, respond so readily to warm periods that may
come in late December or January.

Winter Protection of Buds. The buds of trees in winter are
covered with bud scales. Some hold that the insulation formed
by these scales will keep the buds from reaching a temperature as
low as that of the surrounding air. Wiegand! however, found that
when a thermometer bulb was carefully inserted in large buds there
was no great difference between the rapidity of the fall of tempera-
ture on such a thermometer and one with a naked bulb. He, there-
fore, holds that the bud scales offer little protection in the way of
holding heat in the buds, but that their protection is against evapora-
tion. To test this matter at this station the scales were removed
from buds of peaches in winter before freezing in the freezer pre-
viously described with the results shown in Table 38.

1Bot. Gaz. Vol. 41, pp. 373-424. (Bibl. No. 117).
117

TABLE 38. SHOWING EFFECT OF REMOVING SCALES FROM THE BUDS
BEFORE FREEZING ON THEIR RESISTANCE
TO VERY Low TEMPERATURE.

 

 

 

 

 

 

 

 

 

Number | Number |Percent-|Percent-
. Date Tem- of o age age
Variety of | pera- | Buds. Buds. | Killed. | Killed.
Freezing | ture | Scales | Scales | Scales Scales
Off On Off On
Elberta............. Nov. 12,'09} -15 149 65 2.6 1.5
Elbertainc¢5c0c0 veces Nov. 12,'09| -15 96 133 2.0 1.5
Elbertavec.cc<eea00 % Feb. 23,’10| -18 117 168 47.8 63.6
Elberta, wilted...... Dec. 15,10) -20.2 79 83 59. 81.
Elberta
water-soaked...... Dec. 15,’10} -15 39 35 64. 71.
Elberta,
normally turgid...|/Dec. 15,’10| -15 89 74 46. 75.
Elberta, wilted...... Dec. 23,’10} -21.5 59 57 45. 100.
Elberta, ,
normally turgid....|Dec. 23,’10} -16 56 59 55. 76...
Elberta, wilted...... Dec. 24,'10) -20.5 70 79 74. 100.
Elberta,
normally turgid...|Dec. 24,’10} -20.5 75 75 §2. 32.
Elberta,
water-soaked...... Dec. 27,10] -19.7 60 77 93. 19.
Elberta,
normally turgid...|Dec. 27,’10| -19.7 57 48 57. 75.
Elberta,
water-soaked...... Dec. 28,'10] -20.5 69 72 94. 45.
Elberta,
normally turgid...|Dec. 28,’10| —20.5 54 56 79. 71.
Oldmixon........... Nov. 26,'09) -16 100 87 29. 74.7
Oldmixon........... Nov. 26,’09| -16 98 83 18.4 73.5
Oldmixon........... Nov. 26,’09| —21 80 137 6.2 13.8
Oldmixon...........|/Nov. 26,’09| -21 79 92 2.5 17.4
Oldmixon...........|Nov. 26,’09| —14, 150 151 14.6 62.2
Oldmixon........... Nov. 26,’09| -14 86 96 17.4 47.9
Oldmixon........... Nov. 26,'09} -21 144 198 81.2 98.9
Oldmixon........... Nov. 26,'09| -21 74 76 64.8 96.
Oldmixon........... Dec. 6,'09] —22.5 196 132 15.7 54.5
Oldmixon........... Dec. 6,’09] -18.5 50 290 40. 93.1
Oldmixon........... Jan. 14,’10) -21 185 223 96.6 99.5
Oldmixon........... Jan. 15,’10} -21 218 262 75.6 97.7
Oldmixon........... Mar. 23,10) —10 156 140 57. 57.1
Bell’s Oct., slowly.. .|Feb. 7,'10| -—20 210 107 33.8 83.1
Bell's Oct........... Feb. 8,’10) —-20.5 298 239 46.6 63.6
Bell's: Qcbess csacsiaces ies Feb. 15,’10) -20 267 353 100. 97.4
Bell’s Oct., rapidly.../Feb. 16,’10) —20.5 200 249 100. 100.
Bell's Octisss sseasne Feb. 17,’10) -—20 180 200 100. 98.
Bell’s Oct., slowly... |Feb. 18,’10) -18 121 195 17.3 40.5
Bell’s Oct., rapidly...|Feb. 19,’10) -18 76 245° 82.9 93.0
Bell’s Oct........... Dec. 6,'10} —21 69 100 66. 45.
General Lee, slowly..|Feb. 26,’10] —20.3 233 220 8.5 13.8
General Lee.........|Feb. 26,10} —21 71 111 11.2 19.8
Total number of buds.............--+- 4430 5078
‘Average percentage killed.........+0--Jeeeseereferereees 51.0 68.5

 
118

It will be seen that not only in this case were the scales no protect-
ion against the cold, but in actual fact those buds that had the scales
removed had very uniformly a smaller percentage killed than those
still protected by the bud scales. This is at least true during the most
dormant condition in winter. Toward spring when the buds have
swelled considerably, during warm days, there seems to be practi-
cally no difference between the percentage killed with the scales
removed and those with the scales on. This seems to demonstrate
conclusively that, at least in the case of peaches, the bud scales do
not serve to protect the bud from cold, but as Wiegand points out,
the bud scales serve only to protect the bud from loss of water by
evaporation.

RELATION OF LOW TEMPERATURE TO PEACH GROWING.

Peach Wood Killing. As mentioned previously, on some years
the peach wood is badly injured. Generally this injury follows very
severe cold winters with lower temperatures than are necessary to
kill the buds. However, on some years the wood has been reported
badly injured even when a fair set of bloom followed. It is difficult
to say just what weather conditions favor winter killing of peach
wood in all cases. In the case of young trees, one to three years
old, Emerson! found that in Nebraska they are more likely to survive
the average winter if forced to mature their wood early in autumn,
by using gross feeding cover crops as previously mentioned, though
older trees were not benefited by such a practice. Eustace? reports
that following the severe winter of 1903-04 in New York, peach trees
more than seven years of age were killed worse than peach trees
about seven years of age or younger, except trees one year in the
orchard which killed the worst. Green* and Ballou, following the
same winter, observed that old trees were killed worse than young
trees and that trees kept in a good condition of vigor by use of stable
manure, mulch, etc., were in better condition than trees that had been
permitted to become weak in their growth. This may have been
partly because of the dry weather in early summer followed by wet
weather in latesummer and autumn. The old trees would have been
checked in growth more by the drought and thrown into more succu-
lent growth by the later rains, while the more vigorous young trees
would be better able to secure sufficient water and tend to continue

‘Neb. Agr. Exp. Sta. Bul. 79, 1903. (Bibl. No. 33).
2N. Y. (Geneva) Exp. Sta. Bul. 269, 1905. (Bibl. No. 38).
3Ohio Agr. Exp. Sta. Bul. 157, 1894. (Bibl. No. 48).
119

their growth through the drought, and be just starting into their
normal dormant period when the wet weather began. They would,
not therefore, be so easily pushed into new growth as if they had
passed through a drying out period. At least observation indicates
that the weak tree which ceases growth early in the season is most
readily pushed into spring-like growth in autumn.

It is probably also true that the young tree would offer less
resistance to the movement of sap upward in spring. It would thus
be able to secure sufficient water supply to prevent drying out until
anew layer of sapwood is formed. The old tree would have a greater
leaf surface to evaporate moisture and would offer more resistance
to the movement of sap. It would, therefore, seem possible that the
young tree might recover from the freeze better, though its injury
had been greater than that of the older tree.

In the peach orchards on the Horticultural grounds and at
Brandsville and other points in South Missouri, following the severe
winter of 1904-05 and again following the severe winter of 1911-12,
the trees in a healthy, vigorous condition withstood the low tempera-
ture better than trees in a weak condition of growth. At Brands-
ville and other extreme southern Missouri points, following the
freeze of 1911-12, recovery was much more satisfactory from trees
that had been fertilized with nitrate of soda than with trees that
had not been so fertilized. This was even true with one year old
trees which is contrary to the experience of Emerson,' but it should
be noted that the soil is more conducive to early maturity and the
growing season longer in southern Missouri than in Nebraska.

As to the best means of securing recovery of trees from winter
injury, a great deal depends upon the nature of the injury. Thus
following the winter of 1899, Whitten? reports that trees very severely
pruned, leaving the branches only a few feet long, recovered much
better than trees not headed so severely. Following the severe win-
ter of 1904-05 trees rather severely headed-in recovered better
than trees that had only one-third or one-half of the previous season’s
wood cut off. However, Eustace* found that this severe heading
back of the trees in New York, following the winter of 1903-04, was
very harmful to old trees, though apparently beneficial to young
trees. Moderate pruning gave much better results.

‘Neb. Agr. Exp. Sta. Bul. 79, 1903; (Bibl. No. 33) and Neb. Agr. Exp. Sta. Anl. Rpt. No,
19, 1906, pp. 101-10 (Bibl. No. 35).

*Mo. Agr. Exp. Sta. Bul. 55, 1902. (Bibl. No. 115).

3N. Y. (Geneva) Exp. Sta. Bul. 269, 1905. (Bibl. No. 38).
120

Waite! reports that very severe pruning of trees in Michigan
and other parts of the North, following the same winter, did not give
as good results as light pruning—removing about one-third to one-
half of the one year old wood,—and in Missouri, both in the Experi-
ment Station orchard and in orchards at Brandsville and Hollister
of southern Missouri, old trees that were severely cut back following
the severe winter of 1911-12 did not recover as well as old trees with
even no cutting back. The amount of cutting that seemed to have
been the most desirable, following either the winter of 1908-09 or
1904-05, in Missouri, was in a large number.of cases fatal in 1911-12.
At Brandsville a large block of trees that had reached a height of
something like fifteen feet had their branches cut back to stubs four
or five feet long, and a large percentage of the trees died, after making
some slight growth in the spring, while trees with no pruning or very
light pruning recovered much better.

Just what the difference is it is hard to say, except that pre-
ceding the winter of 1911-12, growth conditions were much the same
as thase described by Waite, Selby and Eustace for Michigan, Ohio
and New York preceding the winter of 1903-04; that is, dry weather
in the early part of the season, followed by very wet weather causing
a late succulent growth.

In deciding how much pruning to give a tree following a severe
winter, one must consider the kind of injury. If the lower part of
the tree is very severely injured, as it will be when the tree is
forced into late succulent growth following conditions that seriously
check its growth earlier, the pruning should probably be such as to
remove not more than one-half of the one-year-old wood, while if
the injury is distributed throughout the tree, and.is not so severe that
the cortex and cambium are entirely killed at any point, it would
seem highly probable that more severe cutting back—say into two-
year-old wood—would be desirable. Such cutting back is often
beneficial to the trees even when they do not need it to help them
recover from severe freezes. However, very severe cutting back,
such as Whitten describes, is probably not the most desirable follow-
ing any kind of a winter since much less cutting will give entirely
satisfactory results and a better tree with more fruit buds for the
following season’s crop. Cutting back to induce recovery from win-
ter injury has always been more successful at this station on young
trees than on old ones and on trees kept vigorous by severe pruning
during previous years than on less vigorous trees. In fact if trees
are old and neglected, severe cutting back all in one year should
always be avoided.

1U.8. Dept. Agr. B. P. I. Bul. 51, pp. 15-19. (Bibl. No. 111).
I2I

Eustace reports that trees pruned in January, shortly after
a severe freeze, gave much better results than trees pruned in March,
probably because a large amount of drying out had been avoided by
reducing the top. At this station better results have been secured
by the early pruning. Fertilizing the soil with a nitrogenous fer-
tilizer, as nitrate of soda or ammonium sulphate, has, at Brandsville,
Missouri, resulted in much more satisfactory recovery from winter
injury. Where the fertilizer was applied both the year before and
the year following the freeze, very slight permanent injury was to
be found when surrounding unfertilized trees suffered great injury.

Hardiest Varieties in Wood. The effect of the condition of
growth on the hardiness of peach wood is so great that it is difficult
to reach an accurate conclusion as to which are the hardiest varieties.
Observations must be on a large number of trees, and through a
large enough number of years to include many different seasonal
conditions. Hedrick,! basing his opinion on replies secured from
New York growers, places Crosby, Hills Chili, Stevens Rareripe,
Gold Drop and Elberta as most hardy in wood; and from replies
from Michigan growers, Hills Chili, Crosby, Gold Drop, Kalamazoo,
and Bernard. Elberta, Smock and Salway, considered hardy in
New York, were considered tender in Michigan. Wager, Jaques
Rareripe, Carman, Belle of Georgia, and Hale’s Early were considered
above the average in hardiness. Eustace? found in New York, fol-
lowing the winter of 1903-04, that Stevens Rareripe, Elberta, Thur-
ber and Salway showed little or no wood injury, while Chinese Cling
was the most seriously injured. R. F. Howard, formerly of the
Nebraska Experiment Station, states in a letter that Russell’ is one
of the most hardy in wood.

At the Missouri Experiment Station there is a peach orchard
that has been exposed to the severe winters of 1898-99, 1904-05 and
1911-12. These trees have had such different treatment that they
necessarily went into winter in conditions not equally favorable
to withstanding the low temperature. We are, therefore, not able
to place the varieties as to hardiness with any degree of accuracy.
However, it can be said with certainty that, although Elberta is very
tender in bud, its wood is exceeded in its ability to recover from such
winters by very few varieties. At least this is true of any but one-
or two-year-old trees. Hills Chili, Salway, Bernard and Gold Drop
have also proved hardy. Chinese Cling has been probably most

1Procs. Western N. Y. Hort. Soc. 1908, p. 180. (Bibl. No. 55).
®=N. Y. (Geneva) Exp. Sta. Bul. 269, 1905. (Bibl. No. 38).
2Yearbook, U.S. Dept. Agr. 1911, p. 429. (Bibl. No. 109).
122

tender in wood, although it is rather hardy in bud. The station
orchard contains no old trees of the Greensboro or Belle of Georgia
varieties but young trees of these varieties, and of Victor and Russell,
were among those that recovered best from the effects of the winter
of 1911-12.

It is interesting to note that Elberta, Greensboro, Belle of Geor-
gia, Victor and Carman are among the more hardy varieties in wood,
and are seedlings of the Chinese Cling, which is one of the few most
tender varieties in wood.

Killing Peach Buds. In the case of fully dormant peach buds
there is but little difference in the killing temperature of the different
parts of the flower. In practically all cases where there is killing
at all, all of the flower parts are killed and, in addition to this, gen-
erally some of the vascular tissue extending down into the twigs
from the base of the buds. This was brought out by careful sec-
tioning of killed buds by Mr. R. G. Briggs. Just how much cold
a fully dormant peach fruit bud will withstand, it seems practically
impossible to approximate. According to Eustace,? the minimum
temperature that prevailed in Western New York in the winter of
1903-04 ranged from -10° F. to -15° F. In most orchards of that
section there was a normal crop although the wood was badly injured,
indicating that under some conditions the bud will actually withstand
a lower temperature than will some of the woody tissues.

In a letter from Professor F. A. Waugh, he says that in Massa-
chusetts practically a full crop of peaches has been harvested from
trees that had been through a temperature of -20° F. and a partial
crop of Greensboro had been secured following a minimum tempera-
ture of about -27°F. Ina letter from Mr. Elmer B. Parker of Wilton
New Hampshire, he states that after a temperature of -14° F. in Jan-
uary, a sudden drop, the Elberta crop was a practical failure while
Carman had 50 to 75 per cent of a full crop, and Belle of Georgia
and Champion had practically a full crop; and in 1910-11 a tempera-
ture of -12° F. in December failed to kill enough buds to prevent
trees from yielding a full crop. In these cases the buds had not
been started into growth by warm periods.

In the year of 1901-02 all of the buds were killed at the Missouri
Experiment Station orchard by a temperature of -23° F. on Decem-
ber 20th. In 1902-03 practically all buds were killed by a tempera-
ture of -15° F. on February 17. In 1903-04 buds were killed on all
varieties except General Lee, Chinese Cling, Thurber, Carman, Gold

1Thesis, University of Missouri, 1912. (Bibl. No. 13).
?New York (Geneva) Exp. Sta. Bul. 269, 1905. (Bibl. No. 38).
123

Drop, Triumph and Lewis, by a temperature of-14° F. on January
29. During the winter of 1904-05 nearly all the buds were killed,
yet practically all trees had a few left alive and Triumph and Lewis
a fair crop, following a temperature of -25° F. on February 13th.
The following table gives the percentage of buds killed for a number
of varieties during the season of 1905-06 and the seasons following
up to 1911-12 when all were killed by a temperature of -20° F. Dur-
ing 1912-13 there was no severely cold weather and practically none
of the buds were killed.

TABLE 39. SHOWING THE PERCENTAGE OF Bups KILLED ON THE
YEARS 1906 To 1911 INCLUSIVE.

February 5, 1906. Temperature -3° F.

 

 

    
 

 

 

3 Number Percentage
Variety Buds Buds
Counted Killed
LG WiS Seca tui may 2 Gk kana eee auaee GMS Se lepie wees 1347 25.9
Chinese: Glin gis 4 iaczijs aise ds deg pin vissanes Sidi ae gig ale bs 599 30.7
S mocha k oe desta dein rie 6 ela cited canara te deena ans Sree ee 559 32.9
Early Michigan: yas022¢¢3 ws4 es esden ae sea. wes 721 =| 32.9
Poole’s Favorite: sis osescsegs ee tae ea oe a we cues 901 - 38.5
SCO siecessccnsi cord bye fdas noe ten RE ROME Sole aes Ge RE 641 41.4
Carma eed d a dGin Wain nk Add ede he 0 eS SEE Ne 617 41.9
Gold Drop............. sian ecattetsoiinaanaa was eseser via wists 744 42.8
STO Wes tay aca cue see ashas Gon wae saya dnss efle te dey oh endastenn eal gums 895 44.2
Gen eralLGees < aie ye teva a guaca a tA Gs aus aladel um muadeteoanele 529 46.5
FAAS CURSE a seeice sexe tsaver aise erpsd eine. SOMA te Oo eed SS! ecwiniee ch 647 50.3
Sal WAY sc ciate Back na 45K sa De POA te een e Vind 675 50.9
Barly Tillotson oiicsccaore aca teae bane, ewe away Seay 541 54.7
Krummel (October. wi. ¢ ccna a ek cee oper wes 539 56.5
Alexander aos osc s aiace ey buscntig pee os Bee Renee we CeO 532 56.9
ONE Z 2 aid cca. Saeed SINS 4 heb ang eID Pst A eeaRe OSs 1930 57.1
Priumphssead she saceeoa easleie sisi: sean hess 1111 59.1
Rareripe.... ads oa 566 59.3
Crosby 'ss.0224 :3me eae ee eds ee 896 60.8
Family Favorite............ Es 1012 61.0
Captain Ede...............-- es 704 63.4
Crawford’s Early.............-20005- er 994 64.1
Bokh ara sc 3.205 cack ou os oraduee Gd yratenearea ens 2 513 67.4
Beige! Red sseiciesicsae ariceseesheeoot bok osu ata oc 0 sa 470 67.4
Elbértaisces. 4 osetia ood ee eee aa oa ai iveae eee 1680 67.8
Oldmixon Cling.......... 0.00 c cece eee ee eens 2080 69.0
TRUPDOES «criatead cares d apes es ee eee Swe ses aa 519 69.1
Henriettass cua acca 24 e a ie eee ree ee yee auns 592 73.9
Glovessinjancads.< Basi ard alialenins Gad GOR ais EAE SHAS 889 76.7
Oldmison, Free... 6 .:¢0scs-eecda ose eos ora esis A ee 1040 78.0
Bitzgeraldi icici cco gone es HO SG AG See Se 641 80.0
Kalamazoo: .¢ access wetsceud ance Sen Wale oi eee Ea GES 1249 80.7
Heath: Cling ici cece ecco cee tie RE HH GG ee 726 81.6
Champion.......... 200 c cece eect e cere ten cenes 608 82.2
Early Bernard........0.00c sees ee ee eee ee erences 752 82.5
Shipley Reds. ei-c gc vale cae ade Sete ne ie se EES 542 88.0
Yellow St. John....... cee eee eee ee eet 512 88.8
Crawford's Latescieiiagn aed viene ee ota how Silden es 677 90.2
Susquehanna. sos cece ie sence cae ee ee ae cane ents 692 96.9
124

 

 

 

 

 

 

 

 

 

 

Number Percentage
Variety Buds Buds
Counted Killed
February 4, 1907. Temperature +1° F.
Early Tillotsones seis guise Go grote eens 535 18.8
Gold Drop: ses sus-neesaviegatae (adbeast sans 765 31.5
Lewi8s ¢.25 cs.i00% ae awe eee SLR eRe SR OY Rae Oy 6 Oe Oe 162 42.5
Oldmixon ‘Cling ss: ii6 0s 2sa0g exis ota ee oes ones 1442 44.4
DSiWM Ph: siecdcceasuaaswe: se Aletaelaseud °F wie RI SS 642 44.8
Poole’s Favorites... ic oii35 ce cseis Siew oo abe: tek corsnrets wea 1003 54.1
PID ERG Ass on: ary ase «asa hae ees ee wee A He Ra te asta orl 409 59.9
S MOCK i eisie ce ese tes soars sold aadcw ook. olen vg GE EASE Meee 804 61.7
Oldmixon Pree) isos cand oe gears ee a va Bae « 504 90.8
February 2, 1908. Temperature +2° F.
Crawford's Early’: «..io3 a-caese glee gate ne oa a BG 250 18.0
FID ORES isi: sce cosauceec. sues ats pre anita dues Sia sdhate ined teauel eee’ 977 35.3
WWalamaZoo.eciccsiace aipsinrs an Sedma ganeneca wera nels. yeaa 8 1104 43.4
Family Favorite ..:c:c0sicce coe voce aa oa ene a a wes 671 44.9
Oldmixon Free....... 0.0... cc eee cece 11242 45.7
OPtiZsn farauide wane eat ha ee eee eget eee 1177 50.8
Sneed so. sacs iatiam ewe saanuiedeatas Sam See aes Gon 1662 §7.5
Dewey Cling. Giowasosud stds Cme-sraslowsie a ea eas Ga 1204 80.9
January 12, 1909. Temperature —11° F.
SL MUG DORs 4.65.6 atten sataen ahs Miah. Hele Ran pea 975 55.2
Early Michigan.............. 02. cece eee aes 463 63.0°-
Heath Cling casio ec necira suc is Mace ee Seapes asda 455 74.7
UNS CAIN occ tocscaysoce pss aaa aang ace ss as fnacdamere ime aee 493 75.2
SMOCK vinci enigs .dusened cag ne ae ne eee eaE EY 230 78.6
Sal WAV isceute sas, oqudiccaiientay hci ates ne ane Seon wee ae 4S 1864 79.0
ORCI Zits 5 vies a caagea ape 8 eh Singers See sg ie lie IRR Gea ns 2355 80.8
SN COA scare sysia's we Se Soa ooh SKE SS -ise b gha 4s ee wspaen anes 333 81,8
Crosb yicce ys ces een hg hii bwic oialougvesebes ine S04 me ohave wheee 520 85.3
General) Leer orcs decccislans a theca d aonncin a's a8 elo wert ey 426 87.7
Family Favorite.......... 0.0... cece ee cece coarse 843 89.9
Dewey Cun csi als its -nsne-aies a5 ate settee eaGies 484 89.9
CHAMPION io iaccnterews Sure od Bacrem ete bale wee wees 550 91.2
Barly Bérard istic gecnaccn cass ae ca ee acce ona eee ex 544 92.2
Bokharae. se igcicas 'cace suse 4am vse v aloes Se Paar ss 1792 92.2
PPTL PD ens cise ex hue aed Hmrereie ig wis aed Rice ae ah 753 93.37
Oldmixon Cling.......... 0... cc cece eee eeeeveee 2994 96.3
Elbertaics sc ye vce oid dle ed matenne ah sug ene es 6634 97.3-
LEZ OMAN csp soa ecscayars diac auattaace: 6 doce «sri g 40a a oee-'eeeig: a 249 97.77
Crawford's Early.......... 0.0. e cen eeeees 848 98.6-
Crawford’s Late........ 00... cece eee cent eeaee 464 99.5 -
Ringold i050 sjsectiahs sates oie asec aaene Bes oeke aie ee Ss 1030 99.5 -
Oldmixon Free......... ccc cece cee ener ecenecs 997 100.0 _
Golden: Gate scsi. o se cada aes au auaeces vec Soins 167 100.0
125

 

Variety Buds Buds
Number Percentag
Counted Killed

 

December 9 and 29, 1909. Temperature —5° F. and -8° F.

 

Chinese: Cling ss ccc six ate ies aie ise 0d agian ean 75 2.6
Family Favorite.............00ceceesuseseeeaee 200 3.0
TCU PW sfc csiats Scde oes asco auaees suanait. ies dudes wldee-d atexvananse 174 7.4
TAL Oy ceariiee aust brace ata occa, anda aic-etate se Beace-tlawetn tana Sects 150 11.3
SCC oa sesra disci: oi diiel g unin Pate dozbew oe, 9 wise eae eae Rava eis 185 12.9
Briggs ROG} sis es euhvsrnaczcoeeenile vee Oaraetadne dé tana 100 13.0
Barly Michifan.icos.. caa ans as ohaida cbse bares’ 126 14.2
General: Le@iiriiet) so gckine asaya ead eye a cites 150 14.6
Sal Way genes sci asd ieSoa baad oie eauet aaa Came ee oe 559 14.9
Oldmixon Brees. cscs o46 5 $e 14 BE A OOLS OS Hie aaa s 200 15.5
AltON oui ne a tales vena canes Ook esa FSA ee eT eas 250 16.4
Rice’s Seedling ics ssw swiscieee ne eee tens beeen 300 17.0
Oldmixon Cling......... 0... cc cee cece cece 200 21.0
COS DY ice sica see ra Mijaco ca teca tee de este ce ccd Siarenw eb loheoS dona 148 22.9
FEUD GR Ea iiss cere Seaein pice auernde dees we adbudasia- arenes aid este 400 24.0
OPC Z io. esansctece Guzessae at guscig seek ale Maa ance also ete ceraatee 200 27.0
Bitzgerald: ices in adhe ee ewe so eaes Mates Paks 100 31.0
Heath: Clraigis ss cc coc chet comand ite tease wa aaa’ 141 . 31.2
Cha MGOn acc icone eas Race aceasta tem nner 150 33.3
Crawlord!s Late... ccscie sc pad tin bie ee ne ee eae 146 44.5
Bokhara ys ce wears ae ase be Baan nas oaks see cian 150 51.3
Barly Berard siiec anes ca te lnsecanin sewew asl ages 100 52.0
Kalamazoo 42's sur s due sa ee a ais ey ace were gee. 2 ane Bee 150 52.6

 

January 3, 1911. Temperature —8° F.

 

Petr p icece sei aisdar ss cpl avet tsa (edeya bvatee aed Sra Gebvw cha 275 29.8
Dall Wa Veni celiwic diliemcnlaye Se eek alc Rie ig ha atels capionsscal ay 309 34.9
FIONTLet tA a3 auhseetec ck eek oes de ee ea ele eee De 237 43.4
Krummel October.............. 00 ee cece ee ences 261 45.9
Crosby acesind atone asp Sepd mie sages Beis cee 530 52.6
Carina ns oie sinuad's aie wages Gi x iewthceieno Serie eee pa 203 52.7
Hea th iC Mi o's g:ciestisceeatta lengriarayelargie cua’ alg) sles caye cadet at 234 58.1
Captain Edewicd. os: 30: csG as ees aeieeae ee asuscce 244 58.1
Early. Bernards: 25 ian: saree eae erees pec bases 253 59.2
Sneed asics ssw HAS ba oe anche x swe ae wae Hee 383 61.3
Kalamaz00 x36 ¢5se see 8s Qe s SR ROE Ce oe 269 74.3
Fitzgerald oie cates ceed MERE MS RR HE SES 253 79.0

 

 

 

It will be seen that on January 12, 1909, practically all the buds
were killed except on the most hardy varieties by a temperature
of -11° F. In fact fewer peaches were borne at Columbia following
the winter of 1908-09 than following the winter of 1904-05 when
the temperature fell to -25° F. on February 13. A temperature of
-12° F. on February 2, 1905, killed only a very small percentage of
the buds of such tender varieties as Yellow St. John. It may be
said too that a temperature of -15° F. on January 7, 1912, killed
practically every peach bud at Koshkonong, Missouri. By referring
126

to the adjoining chart, showing maximum and minimum temperature
curves from December 1st to the date of killing each year at Colum-
bia and at Koshkonong, and for the year 1908-09 and 1909-10 at
Geneva, New York, it will be seen that there was not more warm
weather to start the buds preceding the freeze of January 12, 1909
at Columbia or that of January 7, 1912, at Koshkonong, than pre-
ceding the freeze of February 13, 1905 at Columbia.

It would hardily seem possible that the buds in either case
could have been started into slight growth preceding the freeze.
Buds start very slowly even at high temperature earlyin January. By
referring to the chart it will be seen that the low temperature of
January, 12,1909, came suddenly, following high temperature, while
that of February 13, 1905, came following forty-two days of rather
low terhperature. For sixteen days the maximum temperature did
not go above the freezing point.

There seems to be two possible explanations for the greater
hardiness of the fruit buds during the seasons like that of 1904-05
in Columbia. ~ It is possible that by long exposure to low temperature
the buds develop the ability to withstand lower temperatures. Since
freezing to death of plant tissue seems to result from withdrawal of
water from the cell, the fact that slow drying out of the tissue (see
Table 19) increased the hardiness of the buds would lend weight
to this theory. The cells would be greatly desiccated during the
period of low temperature which preceded the freeze of February
13, 1905. ‘

The other possible explanation of this greater hardiness of the
fruit buds in 1905 is the very slow falling of the temperature (see
Table 20). It will be remembered that the greatest harm resulted
when the rapid temperature fall occurred for the first fifteen degrees
below the freezing point, though rapid temperature fall during the
last ten or fifteen degrees before the killing temperature was reached
also caused greater killing than where the temperature fell slowly
from the freezing point (see Table 21). This station was unable in
its laboratory experiments to maintain a continuous low tempera-
ture that would approximate temperature conditions that prevailed
outside when buds withstood such extremely low temperatures as
in February, 1905. However, buds of varieties known to show great-
er resistance on such winters were not killed by temperatures that
killed buds of varieties like Elberta, known to be tender. The freez-
ing tests in the laboratory then were tests of the relative hardiness
of the buds, either of different varieties or of the same variety differ-
ing in hardiness on account of local conditions. Twigs to freeze
were obtained from New York, from South Missouri, and from
127

Georgia, through the kindness of Professor U. P. Hedrick of the
Geneva, New York, Experiment Station; of the Ozark Fruit Farm
*- Company of Brandsville, Missouri; and of Professor H. P. Stuckey

of the Georgia Experiment Station.

results of our freezings:

The following table gives the

TABLE 40. SHOWING THE RELATIVE HARDINESS OF ELBERTA PEACH
Fruit Bups From NEw Yorx«, SouTH Missouri,

CENTRAL MISSOURI AND GEORGIA.

 

 

 

 

 

 

 

Four freezings Brandsville buds, average

 

Tem-{ Num- |Percent-
Buds from: Date pera- ber age
ture | Frozen | Killed
Geneva, New York.............-.-06- Nov. 27,08] -25 55 |-100
Columbia, Missouri................... Nov. 27,’08} —25 63 {#100
Geneva, New York..............-0055 . 27,08) -17.5 121 33.8
Columbia, Missouri..................- . 27,'08) -17.5 147 68.7
Geneva, New York...... . 12,708) -20.5 152 59.8
Columbia, Missouri.................05 . 12,’08) -20.5 111 37.8
Geneva, New York...............204- . 24,’08) -20.5 129 96.9
Columbia, Missouri.................-- . 24,’08) -20.5 283 67.5
Geneva, New York.................-- . 26,’08} -21.5 195 59.4
Columbia, Missouri................... . 26,'08) -21.5 216 33.6
Geneva, New York.............00000-- . 28,'08) -21 76 81.5
Columbia, Missouri................... . 28,'08| -21 194 57.2
Geneva, New York.............-.006: 1,709) -20.5 73 100
Columbia, Missouri................... 1,709} -20.5 178 57.8
Brandsville, Missouri................- 1,'09) -20.5 95 40.0
Geneva, New York.............-++05- 1,’09| -—22 85 100
Columbia, Missouri.................-- 1,’09| -22 158 83.5
Brandsville, Missouri............--.-. 1,’09| -22 110 44.5
Geneva, New York...............05-- 4,'09| -21.5 32 100.
Columbia, Missouri.............-2.06. 4,09] -21.5 76 59.2
Brandsville, Missouri...............-- 4,'09} -21.5 81 34.5
Geneva, New York.............-0005- 4,'09) -22 26 100
Columbia, Missouri.........-.....-.6- 4,'09| -22 87 78.1
Brandsville, Missouri..............-+- . 4,'09) -22 79 35.4
_ Geneva, New York...........-2--006- . 17,709} -21 159 83.0
Columbia, Missouri........... . 17,'09) -21 282 98.2
Experiment, Georgia . 17,709] -21 124 98.3
Geneva, New York.............0++00- . 19,710) -19.5 115 91.3
Columbia, Missouri................-+- . 19,’10} -19.5 107 92.5
Experiment, Georgia...........----6-- . 19,’10} -19.5 84 98.8
Geneva, New York...........--00000- . 22,'10| -22 130 83.3
Columbia, Missouri...........+--+-0005 . 22,110] —22 219 40.6 ;
Geneva, New York...........--00000- . 25,710) -21 -15- 60.0
Columbia, Missouri............2-++-06: . 25,'10} —21 200 20.0 4
‘Experiment, Georgia..........2-+++005 . 25,710) -21 82 97.5
Geneva, New York........-.00+ee008- . 25,710] -21, 17 76.4
Columbia, Missouri.............0++00- . 25,110) -21 127 58:24
Experiment, Georgia............-02 000+ . 25,10] -21 74 94.5
Fifteen freezings Geneva buds, average........--+++eee cece ec eeeee 81.8
Fifteen freezings Columbia buds, average.. ia

 

 
128

It should be said that there were more immature or partially
developed buds that were killed by a rather high temperature on the
twigs from Geneva than on the twigs from either Columbia or Brands-
ville, which probably explains the higher percentage of buds killed
on the Geneva twigs.

It will be seen that except when the freezings were late in Feb-
ruary when buds in Missouri had been started into growth by warm
days, the buds from New York were not more hardy than those of
the same variety from Columbia. In the preceding chart will be
found curves showing maximum and minimum temperatures for Ge-
neva, New York; for Koshkonong, Missouri, six miles from Brands-
ville, Missouri; and for Columbia, Missouri.

It will be seen that the buds from Geneva, New York, had been
exposed to lower temperature and to more continuously low tem-
perature preceding the freezing. Yet when they are thawed before
freezing and the temperature fall is equally rapid; there seems to
be no difference between their hardiness and the hardiness of buds
from central or southern Missouri. It is possible that the buds
from New York were started into some growth in transit shipment
having been made by express. However, the buds from Bransdville,
Missouri, came in the same way and, on account of poor railway
connections into Columbia from the South were about as long in
coming. If they were not as long in coming, they were kept in a
rather warm basement room until the New York twigs came. While
the data are not such that absolute conclusions could be drawn, at
the same time they certainly seem to suggest that the buds from New
York had not acquired appreciably greater hardiness due to their
having been previously exposed to low temperature. It seems possi-
ble that the buds are more resistant to a low temperature at the end
of a long cold period than are equally dormant buds to a low tempera-
ture that comes with a sudden drop, not so much because of a greater
resistance of the protoplasm brought about by prolonged exposure
to low temperature as because of the very slow temperature fall.
If this be true, a freeze following a thaw in winter should result in
greater injury than if there were no thaw, even if the temperature
during the thaw does not go high enough to cause growth. This
seems to be the experience of growers in the North. Letters from
men in Connecticut, New Hampshire, and the peach regions of Can-
ada state that with them killing of the buds generally occurs when
the cold period follows a thaw. It would hardly seem possible that
weather warm enough to start growth would be experienced in those
sections. It would seem more probable that the killing results from
129

the rapid temperature fall, while the greater resistance of the buds
following a prolonged cold period is due to the very slow temperature
fall with the resulting slow withdrawal of water from the cells, es-
pecially while the temperature is still near the freezing point. (See
Table 21.)

The condition of the tree when it enters the winter should not
be lost sight of in considerations such as the above on the killing
from cold in winter. As mentioned previously, maturity plays an
important part in the resistance of winter tissue to low temperatures.
It may be said, however, that reference is had to the same trees for
1905 as for 1909. They were older in 1909 and were unquestionably
as mature. In fact in 1909 there was no apparent difference be-
tween the hardiness of buds on the most vigorously growing trees
and those growing most slowly in this orchard, indicating that all the
trees went into the winter in good condition. That the condition
that favors greatest hardiness of buds is one of greatest maturity is
_ apparently common knowledge among peach growers in northern
sections. On each such winter in the Missouri Experiment Station
orchard these trees that had ceased growing and become dormant
tather early the season before carried the largest number of buds
‘through the extreme cold uninjured. The same phenomena were
observed in Southwest Missouri following the winter of 1911-12
when there were no warm days to start the buds preceding the ex-
treme.cold that killed them. In this case only those trees that were
large and matured early and had a large amount of small growth
down in the tree had any large percentage of buds tosurvive. These
same phenomena have been observed in orchards on other years in
Missouri. However, the average buds on a later maturing tree do
not seem to be appreciably less hardy than the average buds on ear-
lier maturing trees. In nearly all cases those buds that survived
were buds located on small spurs where there would be a whorl of
three or four leaves with only one or two buds on the spur, and there
are few such buds on a heavily pruned late maturing tree. It was
shown in Bulletin No. 74 of the Missouri Experiment Station that
generally the largest percentage of buds to survive cold are on the
base of the twigs of mature size; the next largest on these small spurs
mentioned above; and the smallest percentage to survive will be on
the ends of the twigs. However, with extreme cold that will kill all
of the buds at the base of the main twigs or practically all of them,
there will often be a few on the spurs; that is, the buds on these spurs
vary more as to hardiness than do the buds at the base of the whips.
This would naturally be expected since the condition of growth with

9
130

reference to light, etc., will vary more. While the percentage of
buds surviving on the tree when enough are killed that practically
all left are on these small spurs, would naturally be very small, it
should be remembered that only a very small percentage of buds ona
large healthy tree would be sufficient for a crop that would be profita-
ble to handle. Under conditions when the buds are killed in a fully
dormant state, or are killed after some starting following a warm
period coming late enough in the season so that the rest period does
not affect the amount of starting, the best plan for handling the trees
is to prune them down to a size that can be conveniently handled
in spraying, pruning, picking, etc., and to practice a system of prun-
ing and cultivation such that they will cease growing as early as
August in central Missouri.

Varieties With Most Hardy Fruit Buds When Fully Dormant.
There is a great difference in the degree of cold that different varie-
ties will withstand even when fully dormant. Hedrick gives a list
of the hardiest varieties for New York and for Michigan, basing
his conclusions on letters received from a large number of New York
and Michigan growers. The New York growers name Crosby, Hills
Chili, Triumph, Gold Drop, Stevens’ Rareripe, and Kalamazoo as
being the most hardy in bud, Crosby and Hills Chili being listed by a
much larger number of growers than either of the other varieties.
Hills Chili, Gold Drop, Crosby, Kalamazoo, and Bernard are the
hardiest varieties, according to the opinion of the Michigan grow-
ers. Waugh lists Greensboro as one of the hardiest under Massa-
chusetts conditions. Growers in the northern part of Missouri have
also found Greensboro probably the hardiest peach in bud that they
have grown. Judging from years when the buds were killed without
any starting into growth by previous warm periods, Hills Chili,
Lewis, Thurber, Gold Drop, Triumph and Crosby have been among
the very hardiest in bud in Missouri. Lewis is a seedling of Hills
Chili. Mr. R. F. Howard, formerly of the Nebraska Experiment
Station, and others in Nebraska place Russell,! another seedling of
Hills Chili, as one of the very hardiest of peaches in bud, as well as
in wood.

In Missouri, besides Greensboro and Thurber, Carman, Belle
of Georgia, General Lee, and Chinese Cling, and some other varie-
ties of the Chinese Cling group, have been more hardy in bud even
under fully dormant conditions, than the majority of the well known
varieties. The Green Twig group, especially Snow and Rice’s Seed-

1Yearbook, U. 8. Dept. Agr. 1911, p. 429. (Bibl. No. 109).
131

ling, have been found hardy under the same conditions. Champion
is also above the average in hardiness under fully dormant conditions,
so far as observations in Missouri indicate.

Of the more tender varieties when fully dormant Hedrick lists,
from the opinion of New York and Michigan growers, Crawford’s
Early, Crawford’s Late, Chairs Choice, Reeves’ Favorite, and
Elberta.

In Missouri these varieties are among the most tender on such
years under Missouri conditions, with other peaches of the same
type as Golden Gate running even more tender, and Oldmixon Free
and Cling and the Heath Cling group, and Fitzgerald and Early
Bernard, being slightly more hardy.

Rest Period of Peach Fruit Buds. During some of the seasons
mentioned above, especially that of 1905-06, a large percentage of
the buds were killed at a high temperature because they had been
previously started into growth by warm weather. By referring
to the temperature chart it will be seen that on many years in Co-
lumbia, and on a large majority of years at Koshkonong in the extreme
southern part of Missouri, the temperature for December, January
and February will average as high as for those three months in Co-
lumbia in 1905-06. 2

During the writer’s observations there has very seldom been
a year when buds in the peach section of southern Missouri have
not been started sufficiently by February 1 to be killed by a tem-
perature considerably higher than would be required to kill buds
in northern Missouri, or certainly in Michigan, New York or New
England on the same date.

VARIETIES WITH THE LONGEST REST PERIODS.

Any one who has had experience with a large number of varieties
of peaches in a climate like that of southern Missouri has observed
that there is a wide difference between the amount of starting by Feb-
ruary 1 on different varieties. Thus it will be seen by referring to
Table 39 that a smaller percentage of buds were killed on February
5, 1906, by a temperature of -3° F., following a warm period, on Gen-
eral Lee, Chinese Cling and Sneed of the Chinese Cling group, and
the Green Twig varieties such as Snow and Ortiz, and on Lewis and
Early Michigan of the Hills Chili group, than were killed on varieties
like Crawford’s Early, Elberta, Fitzgerald and the Heath Cling
varieties.
132

Experiments at this station have indicated that the reason
for this is because these varieties havealonger rest period. Attempts”
to force the buds of various varieties into growth in the early part
of the dormant season, by keeping the twigs in the greenhouse with
their bases in water, were published in Bulletin No. 74 of the Missouri
Experiment Station. The following table summarizes those results
for some of the different types of peaches, giving also the percentage
of the buds killed by a temperature of -3° F. on February 3, 1906,
when the killing at so high a temperature was due to the buds having
been started into growth by previous warm days.
133

TABLE 41. PERCENTAGE OF Bups THAT COULD BE STARTED INTO
GROWTH BY DECEMBER 12, AND DECEMBER 22, 1906,
ON VARIETIES OF HILLs CHILI, CHINESE CLING,
GREEN TWIG AND OTHER GROUPS.

 

 

 

 

 

. Percentage | Percentage | Percentage
Variety of buds of buds of buds
killed in started by started by
1905-06 Dec. 12, 1906]Dec. 22, 1906
HILLS CHILI TYPE
FNS CWI sate cide dealacadateduaiate 53.0 5.2 Nodata -
TSO WAS asso vasaeevbecaiccepanansinnuens duienarorane lat 25.9 0.0 39.0
Early Michigan.................5. 32.9 5.7 42.4
IA VOT ARE iaieiie soscner a saaits sn potaae set annreasicen alate 37.2 3.6 40.7
CHINESE CLING TYPE
Chinese: Clings saicvnaeoenesweasae 30.7 0.0 0.0
Genéral Lees. isicne xem ewe sv eases 46.5 0.0 0.5
Sneed as cncisews asa ses cae sae ens 41.4 0.0 8.0
Carman).....3. 552000 omasees cee ows 41.9 No data 25.0
CONNEtE sc cssncinaie a beeees. ge eas 40.0 0.0 0.0
Family Favorite.................6. 61.0 0.0 7.0
Elberta............. waa su dieseliansua anaes 67.8 No data 56.0
fe VELA RC hein ovina ere ceseininrs aunie sajousscane 47.0 0.0 13.8
“ Average (excluding Elberta):..... 43.6 0.0 6.7
GREEN TWIG VARIETIES
SMO Wor ciara wiereys-avataia ensere supine ares avers 42 0.0 “12.0
ORE Zia iors coskertatavena’ enarnaleles wuanacarsnets 57.1 0.0 5.4
Averagesscesccrvees der wns wees 49.5 0.0 8.7
HEATH CLING TYPE
Heath Chi... ccscacccassceseicne eee Biase « 81.6 17.5 86.0
Dewey Cling...........-20eeceeee 74.8 36.7 88.0
‘Hubert Cling..........0. 00 eee eee 77,2 27.4 85.0
Rite Ol eh sascczscteasesise aiss-onsendids «enoestecent ahs 83.0 30.0 88.0
} AVEra SG rsauauiesmeremarwa daa 79.1 27.9 86.7
OTHERS OF PERSIAN RACE
Wibertaiscaven:araswexawaaieetaanes 67.8 No data 56.0
‘Crawford’s Early..........e+000-- 64.1 No data 54.1
Crawford’s Late........---++0e005 90.2 No data 59.0
Oldmixon Free.........--02 0000s 78.0, No data 98.0
OSEER 4 jy oa ct ayemecalaonessreat sites aR 87.0 No data 83.0
CROSBY cs iscuitse wasane- atone ecessnanteas th MaCe a 60.9 22.8 90.0
Susquehanna..........0+-eeeeeeee 96.9 10.0 65.0
Wieatland™ soca viscase vegicre nace acanere seeds 95.4 No data 86.0
Golden Gate........2-2eeeeeeeeee 89.7 17.7 58.0
THM p Nerrerrecrrneieise cues age osarels iene 59.1 0.0 7.5
AVETABE ..c05 xen see ewiela awe etalon 78.9 12.6 65.7

 
134

It will be seen that especially the Chinese Cling group of peaches
and the green twig varieties have a long rest period and can not be
readily pushed into growth by warm periods earlier than about
January 20th, while such varieties as Crawford’s Early, Foster and
all of the Heath Cling varieties could be much more readily pushed
into growth in the early season. Fitzgerald and Early Bernard are
not included in these experiments, but experience with them proves
that they have as short a rest period as Crawford’s Early, and are
equally tender under Missouri conditions. Elberta, a Chinese
Cling seedling, the other parent of which is thought to be Crawford’s
Early, has a short rest period like Crawford’s Early, while Carman
resembles the Chinese Cling in bud habits. Since the publication
of Bulletin No. 74, there has been opportunity to observe the pushing
during late February on Carman as compared with Elberta in south-
ern Missouri, and uniformly the Elberta pushes much more rapidly
during January and February, and even March, than Carman, and
on nearly every year it blooms earlier, though in North Missouri
where peaches bloom later and the effect of the rest period will thus
be entirely eliminated before blooming time, Carman and Elberta
are likely to bloom together.

EFFECT OF VIGOR OF THE TREES ON THE REST PERIOD.

It was found as published in Bulletin No. 74, Missouri Experi-
ment Station that prolonging the growth of peach trees in the fall
will prolong the rest period so that the fruit buds are not so liable
to be killed by cold periods following warm periods. This prolong-
ing the growth in the fall was generally accomplished by pruning the
trees severely, in this case two years before those tests were made.
This caused them to grow more vigorously throughout the summer
and to continue growth later and to hold their leaves late in autumn.
While the more vigorous growth continued through the second sum-
mer after the pruning, the additional vigor over the unpruned trees
was not so great.

To test the effect of this additional vigor on the rest period,
twigs gathered on various dates from November 23 to January 13
were forced from two to three weeks in the greenhouse. Following
is a summary of the table published in Missouri Experiment Sta-
tion Bulletin No. 74, giving the result of these tests made during
the season of 1906-07. The vigorous, pruned trees are termed “cut
back”’ trees.
135

Average percentage started on trees making large growth (cut

LCE) ses spe Sci teee§ scot crea fone Gomi uat aaitig tec auesyp colina eat ectin Nn gies
Average percentage started on trees making small growth (not
TLE AL CIE)) ages acca avandia coh act cease ance ld hecandn tibia devgac dieibasevdansraa amie rSiarease 31.2

Number of varieties in which trees not cut back started first.. 20.
Number of varieties in which trees cut back started first........
Number in which both started about equally.................. 4

Quoting from the publication referred to:

“Tt will be seen that only two-thirds as large a percentage of
buds started on cut back trees as on trees not cut back. It would
be expected then that when ninety per cent of the buds had started
on trees making small growth, only sixty per cent of those on trees
making a large growth would be started. This is borne out in the
above table. If we take the average of buds started on twigs taken
December 22nd, or later; that is, when the resting period is nearly
ended, we have:—

“For trees making large growth (cut back) 28.3 per cent started;
for trees making smaller growth (not cut back) 48.6 per
cent started.

“Taking only those varieties in which one tree had sixty per
cent of the buds started, and therefore may be considered to have
finished its resting period, we have as an average:—

“On trees making large growth (cut back) 44.3 per cent of the
buds started;

“On trees making smaller growth (not cut back) 83.4 per cent of
the buds started.”

Results during the previous season when the difference in vigor
of the trees was greater, were even more conclusive though perhaps
not enough buds were used in the experiment. Thus with Elberta
buds on twigs gathered December 2, 1905, 66 per cent of those from
slowly growing trees clearly showed swelling by December 21, while
none from the vigorously growing cut back trees showed any swelling.
Even when the buds from vigorous trees were counted as started,
they had not generally made as much growth as had those from weak
trees. It should be said, too, that the trees listed as weak trees
were of average vigor when compared with those of most commercial
» orchards.

Since the publication of that bulletin this station has made ob-
servations on the effects of severe pruning and late growth on the rest
period of buds in the extreme southern portion of Missouri where
there are many days in January and February warm enough to start
136

growth. It has been generally found that the buds on weak trees
are more forward than on trees that have grown late in the fall. At
Doniphan, Missouri (in one of the extreme southern counties) dur-
ing the spring of 1908 in an orchard owned by a Mr. Neal, old Elberta
trees that had been weakened by late summer pruning and others
that had not been pruned at all were in full bloom by March 15, while _
young Elberta trees that had been severely pruned the spring and
late winter before were not yet in bloom, being apparently at least
one week more backward in blooming than the weakly growing
trees. Other orchards in the same community showed similar condi-
tions. It should be said, too, that this was not an abnormally early
bloom for extreme southern Missouri.

During the spring of 1910 a number of Elberta peach trees were
pruned back very severely in the orchard of the Ozark Fruit Farm
Company at Brandsville, Howell County. The following winter
was so abnormal that nearly all Elberta trees were almost in full
bloom by February 22, when a temperature of 14° F. was experienced.
Of course the bloom and some of the unopened buds on such trees
were killed. At that time the fruit buds on these severely pruned
trees that had grown late in the fall were not open, and they suffered
much less injury than did buds on trees not cut back.

Again on March 16 a temperature 20° F. was experienced. Buds
on these cut back trees had not yet reached the stage of development
that had been reached by trees not so treated by February 22, the
temperature between those dates being too low for much growth
to take place. The following table gives the percentage of buds
killed on the severely pruned and on the unpruned trees by the freeze
of February 22, and by the freeze of March 16.

TABLE 42. SHOWING THE PERCENTAGE OF Bups KILLED AT BRANDS-
VILLE, MISSOURI, BY THE FREEZES OF FEBRUARY 22
AND Marcu 16, 1911, oN SEVERELY PRUNED
AND UNPRUNED TREES.

 

 

Percentage Percentage
Total of Buds of Buds
Treatment Number Killed by Killed by
of buds Freeze of Freeze of
Feb. 22, 1911 | Mar. 16,
1911
Not cut backy sss cusesapeanciveds as 104 85.6 98.08
Cub bakes ra.e 45 eapi-e doe 22k id wines ack’ 183 48.1 81.9

 

 
137

Thus 18.1 per cent of the buds on these cut back trees were still
alive after the two freezes. These trees set practically a full crop
while trees around them bore not more than one or two peaches to the
tree. On the same year, trees heavily pruned the previous spring at
Doniphan, Missouri (another southern county), were more than
three weeks later in blooming than trees not so treated, as reported
by Mr. J. R. Stevens.

The rest period can also be as readily prolonged by fertilizing
with a nitrogenous fertilizer, thus prolonging the growth into the
fall. In the Brandsville orchard mentioned above, in 1910 a plot
of trees was heavily fertilized with ammonium sulphate. One plot
of thirty trees received 100 pounds and another plot of sixty trees
received 100 pounds. The following table gives the percentage
of buds killed on those trees receiving the heavy applications of
fertilizer on February 22 and on March 16, and also the percentage
killed on adjoining trees not so treated, and on trees fertilized lightly
with sodium nitrate in 1909 and in 1910:

TABLE 43. SHOWING THE PERCENTAGE OF Bups KILLED AT BRANDS-
VILLE, MISSOURI, BY THE FREEZES OF FEBRUARY 22
AND Marca 16, 1911, on TREES FERTILIZED
WitH NITROGEN AND TREES
Not so FERTILIZED.

 

 

Percentage Percentage
Total of Buds of Buds
Treatment Number Killed by Killed by
of Buds Freeze of Freeze of
Feb. 22, 1911 | Mar. 16,
1911
Fertilized with Ammonium Sulphate 312 44.6 77.6
Check, not fertilized............... 188 91.5 98.4
Fertilized with Sodium Nitrate 12
Ibs. to the tree in 1909 and 1 Ib. to
the tree in 1910................. 225 80.4 87.1

 

 

On the trees fertilized heavily the spring before with ammonium
sulphate a percentage of buds large enough for a full crop was left
after both of these freezes, and the trees set and ripened a full crop
of fruit, while the adjoining trees had nothing. Trees fertilized with
sodium nitrate, but not so heavily, did not show such marked results,
and yet there were enough buds left for a fair crop, if all the orchard
138

had set as much so the activities of the curculio would not have been
concentrated on so small an area.

It may be said also that trees on another plot fertilized with
sixty-three pounds of sodium nitrate to thirty-six trees in March,
1909, had a smaller percentage of buds killed during the winter of
1909-10 and set a heavier crop in 1910. From these results it is
evident that where there are a large number of warm periods in the
early part of the winter before the rest: period is entirely ended, any-
thing that prolongs the growth in the fall greatly reduces the per-
centage of buds killed. In fact from the southern tier of counties
in Missouri, south, even where the freezes follow warm days as late
in the season as February, it will still be a benefit to have the trees
grow late in the fall, as witness later blooming of the more vigorous
trees mentioned above.

It should be said with reference to the ending of the rest period,
that so far as we can tell, this does not occur at a definite time, but
buds that will push very rapidly when taken into a warm greenhouse
in March can be pushed in January or early February, but not nearly
so rapidly; so that whatever the ending of the rest period is, it is cer-
tainly a gradual process. While the differences between the rate
of pushing on vigorous and weak trees would be smaller following
warm days late in the season, say in February, than as early as De-
cember and January, yet with trees in extreme southern Missouri,
there are some differences to be observed as late as February or March
as mentioned above. This was certainly true in the case of blooming
of peaches in February, 1911, when the more vigorous trees did not
bloom until more than a month later than weak trees bloomed. How-
ever, in years when the bloom is rather late there will be little or no
difference between the blooming of vigorously growing and weakly
growing trees. Thus in the spring of 1913 the full bloom on Elberta
trees that were fertilized with sodium nitrate in the spring of 1912
and those that were not, came at practically the same time, which
was approximately April 5. Carman, though, was at least four
days later in coming into full bloom than Elberta, and Carman from
our experience has a longer rest period than Elberta.

As far north as Columbia, Missouri, where the peach bloom
is never earlier than March 20, and is usually in April, weak trees
have never bloomed earlier than vigorous trees, and varieties like
Carman, Chinese Cling, etc., have never bloomed during our observa-
tions later than trees with a shorter rest period. Thus neither by
forcing late growth to prolong the rest period nor by choosing varie-
ties, such as those of the Chinese Cling group, with long rest periods,
139

can the date of blooming often be appreciably affected as far north
as Central Missouri. In southern Missouri, on account of the pro-
tection from early autumn frosts rendered by the excellent air drain-
age and on account of its being further south, the trees grow later in:
autumn and for the same reasons, blooming is likely to occur from a
week to occasionally six or seven weeks earlier than in central Mis-
souri. Thus the season there between the beginning of dormancy
and blooming time is often short enough that the influence of the
rest period may be observed even at blooming time. Trees of varie-
ties with a long rest period or trees that grow late in autumn will
bloom later, as in the case of the pruned and fertilized trees mentioned
above.

Relation of Thinning the Fruit to Hardiness. Another phase
of orchard practice with which it seems it would be possible to in-
fluence the rest period, is thinning the fruit. In tests reported in
Bulletin No. 74 of the Missouri Experiment Station where trees had
one-half of the fruit thinned and the other half left to bear a full crop,
out of five trees so treated in each case during the following winter
a larger percentage of buds were killed on the side that was not
thinned than on the side that was thinned, and where the thinning
was very heavy or where all of the fruit was taken off, the difference
was very marked. The following table gives the results:

TABLE 44. SHOWING EFFECT OF THINNING ON HARDINESS, BUDS
STARTED INTO GROWTH BY WARM PERIOD
BEFORE END oF REST PERIOD.

 

 

 

 

 

Percent-
Number age
Variety Treatment of Buds of
Counted Buds
Killed
Seedling......... Fruit thinned... ................ 1529 18.5
Seedling......... Fruit not thinned................ 1657 58.9
Elberta Seedling..| Fruit thinned................... 1020 31.6
Elberta Seedling..| Fruit not thinned................ 1146 36.7
Oldmixon Cling....} Fruit thinned.................... 1442 44.5
Oldmixon Cling....| Fruit not thinned...... BYigtacasanenstarans 1149 53.4
Poole’s Favorite..| Fruit thinned... .............--- 818 41.7
Poole’s Favorite. .| Fruit not thinned................ 807 52.8.
Poole’s Favorite..| Fruit thinned................... 1563 40.9
Poole’s Favorite..| Fruit not thinned................ 1200 55.4
Averape; (thinned) aise sain esoes See en cn sea eae Vee ae eANe hag ate 35.4
Average (not thinned)....cscseesws es oe cer ans vee seen stare aseunne 51.4

 
140

During the season of 1908 this study was continued and we
have the results for the freeze of January 12, 1909, where the killing
was not caused by cold periods following warm periods, but by cold
periods when the buds were fully dormant. In this case there was
no difference in the hardiness due to thinning, as the following table
shows:

TABLE 45. SHOWING THE PERCENTAGE OF Bups KILLED ON
THINNED AND UNTHINNED LimBs OF TREES WHEN THE Bups.Hap
Not BEEN STARTED INTO GROWTH BEFORE THE FREEZE.

 

 

 

 

Percentage; Number | Percentage
Number of of Buds
Variety Date of Buds Buds Buds Killed.
: Thinned Killed. Not Not
Thinned. | Thinned. | Thinned.
Salway........... Jan. 12,’09 345 74.5 425 , 84.7
Ringold........... Jan. 12,’09 397 99.8 289 98.6
Family Favorite...|Jan. 12,’09 274 90.8 569 89.1
Elberta........... Jan. 11,’09 323 99.4 334 94.4
Elberta........... Jan. 12,’09 613 85.3 454 £86.5
Elberta........... Jan. 12,’09 538 99.9 608 100.0
Triumph.......... Jan. 12,’09 292 92.1 242 90.9
Magnum Bonum....|Jan. 12,’13 308 100.0 250 99.2
Crawford’s Early..jJan. 12,’09 412 99.2 436 97.9
Alexander......... Jan. 12,’09 230 94.7 194 91.2
Oldmixon Free.....|Jan. 12,’09 152 100.0 182 100.0
Hills Chili.........|]Jan. 12,’09 397 94.9 405 95.0
Bonanza.......... Jan. 12,’09 421 95.9 352 96.8
Early Michigan....|Jan. 12,’09 145 84.8 496 82.8
Early Michigan....|Jan. 12,’09 243 78.6 154 79.8
Total number buds........... 5090 |eccc sae cen 5390
AN OLA GE ails we Alee hued sudieta dios 4 | WE-deoe abet O32 leary dines 92.5

 

 

 

 

During the same season artificial freezings of buds from the
thinned and unthinned sides of these trees were run, and in this also
there was no constant difference between the percentage of buds
killed from thinned and unthinned limbs. These results suggest
that thinning has its effect on the rest period rather than on the in-
trinsic hardiness of the buds. Where the tree is bent under a heavy
load and under the strain of bearing a heavy crop, as when it is not
thinned, the moisture supply probably being partially shut off, the
same condition will prevail, at least to some extent, as when the trees
are not cultivated; they will become dormant earlier and end their
rest period earlier. Thus thinning, like heavy pruning and fertiliz-
ing with nitrogen can be expected to increase the hardiness of peach
141

fruit buds only in climates like that from Central Missouri South,
where there is likely to be weather warm enough to start the buds
_ into growth before the effect of the rest period ends.

It may be said also, especially concerning thin soils such as are
to be found in the Ozark regions of Missouri and Arkansas, if the
tree is permitted to bear an exceptionally heavy crop, it sets a much
smaller number of fruit buds. While experiments have not always
indicated that this is true with apples, any one who has had an op-
portunity to observe a considerable number of peach orchards where
only part of the trees have been thinned will be readily convinced
that it is true with peaches. This fact has its bearing on the problem
of killing from cold since with a very light set following a heavy crop,
if as many as 75 per cent of the buds are killed, there will not be
enough buds for a good crop, while if the trees were thinned, 25 per
cent of the buds would be enough for a heavy crop. By consulting
Table 39 it will be seen that in a large number of years as many as
78 per cent of the fruit buds are killed on Elberta trees. In sections
like South Missouri where the rest period seriously affects the amount
of bud killing, thinning, when necessary, would thus seem to affect
the size of the following crop on nearly every year.

The greater hardiness in late winter of fruit buds on severely
pruned trees and on trees fertilized with nitrate, like those mentioned
above, represents a difference in time of ending the rest period be-
tween fruit buds on very vigorous trees and on trees of medium vigor.
Where the rest period was prolonged by thinning, the difference in
hardiness represents a difference in time of ending the rest period
between fruit buds on trees of medium vigor and on trees in a rather
weak condition. In case of trees making a weak growth for any
reason, as compared with trees making a moderately vigorous growth,
so far as our observations have gone, the differences while not so
great, are yet often apparent. In a number of years the buds or
blossoms have been so nearly all killed that the crop in extreme South
Missouri on weakly growing trees, amounted to nothing, while trees
of medium vigor, like an average six-year-old tree, bore good crops
in the same years.

In attempting to increase the hardiness of peach buds under
the climatic conditions prevailing in southern Missouri, by largely
increasing the vigor of growth over the average growth, several
limiting factors must be considered. In the case of pruning, such
large increase in vigor of growth can practically be secured only fol-
lowing winters or springs when the fruit buds or blossoms have been
killed, since this cutting back so severely in other years would cause
142

the loss of the crop following the spring it is done. However, in the
Missouri peach section on all except the high land, at least, the crop
is likely under average conditions to be lost probably half of the
time and in such yearsit certainly is advisable to give the trees rather
severe cutting back. In none of the experiments above mentioned,
however, has it proved an advantage to cut the limbs back so severely
that only short stubs, say two or three feet long, are left. In this
case the growth will be so vigorous and there will be so much shade
that very few fruit buds will form, during the following summer.
The tree will also be so greatly reduced in size that even though a
crop may be secured the year following, there will be bearing surface
for only a small crop. Cutting back into two-year-old wood or
sometimes into three-year-old wood and shearing the small growth
off the limbs so that there will be only stocky, vigorous twigs to form
in summer, has secured the best results. The cutting back should
be light enough that buds will form practically to the base of all of
the new twigs. With pruning like this a large bearing surface is
left and a large number of buds generally set. Observation has uni-
formly indicated that following periods when part of the buds are
killed, most of the fruit will be borne on the twigs down along the
limbs rather than on the very vigorously growing twigs that form
along the top of the limbs. No such twigs will be formed along the
limbs where the tree has been given too heavy pruning as where the
limbs are left only three to five feet long.

For these southern Missouri conditions the pruning in years
when there is a crop should be as severe as can be given and yet se-
cure a maximum crop of the best quality of fruit from the tree. If
this is practiced there will be later pushing of buds the following
winter and in some years a slightly later blooming on trees so pruned
than on trees that have had less pruning. However, where the soil
is very thin it may be impossible to keep the trees in a sufficiently
rapidly growing condition to secure a prolonged rest period without
too greatly reducing the size of the tree. In this case the vigor
should be kept up by a combination of pruning, cultivation and
fertilizing with nitrogen (or a complete fertilizer if it is proved that
other elements than nitrogen are needed in the given soil).

In fertilizing with nitrogen, however, to keep up the vigor of
the trees, caution should be used because heavy applications of nitro-
gen-bearing fertilizers seriously injure the color of the fruit borne the
summer following, and cause fruit to rot. This has been our experience
each year at Brandsville, Missouri. Increasing the vigor by pruning
does not have this effect to any appreciable extent, but generally
143

tends to improve the quality of the fruit by increasing its size. Fer-
tilizing with nitrogen should be as light as it is possible to give and
yet keep up proper vigor and size of the tree by combining nitrogen
fertilizing with pruning and good cultivation. This may be said,
however, that since it has become the regular practice to spray
peaches, this injury to color is not so serious as it formerly was be-
cause the spraying burns into the peach generally a rather brilliant
color. If in addition to spraying the fruit is thinned and the trees
kept well open, the injury to color and diminished resistance to rot
from the use of nitrogen is not so great.

Probably under average conditions a good system to follow
would be to fertilize with the equivalent of one or one and one-half
pounds of sodium nitrate to the tree and to prune as much as possible
without reducing the crop of high-grade fruit in any year. The ni-
trogen should be applied not every year but only often enough to
maintain the desired size of the tree, since the pruning has a dwarf-
ing effect. It may be observed that inducing vigorous growth will
.causé a late growth in autumn; and that therefore the fruit buds
and wood will not be in a desirably mature condition for winter.
This is certainly true in some northern sections and in case of buds has
in several years since 1901 been true in Columbia. Since 1901 there
has probably been only one winter when a larger percentage of buds
were killed on late growing than on early maturing trees in extreme
southern Missouri, and even in that year-1911-12—the wood of the
vigorous trees best recovered from the effects of the winter. It
should be remembered that in southern Missouri the soil is so light
and the season so long that it is not easy to prolong the growth of a
peach tree more than two years from planting enough to prevent its
going into winter in the best condition for that section.

It may be said that before recommending a method like this
for increasing the hardiness of buds, it probably should be tested
out during a period of ten or twelve years so that observations will
extend through enough seasons that one may be sure he has struck an
average. However, this may be said, that the methods here rec-
ommended are certainly the best for the orchard, regardless of the
effect on the hardiness of the tree. Fertilizing with nitrogen has
caused the tree to resist certain diseases like shothole fungus, as well
as to recover from the effects of winter freezes, heavy crops,
etc., and has, of course, given a larger tree that could bear a much
heavier crop. Heavy pruning has had similar effects except that
144

it generally tends to reduce the size of the tree, though in very thin,
dry soil, heavy pruning has also increased the size of the tree.

Whitewashing Twigs to Retard Bud Growth. Another means
of holding the buds dormant in winter is to keep all twigs and buds
covered with whitewash. This keeps down the temperature of the
buds during warm days by reflecting heat that would be absorbed
by the dark colored pigments in the twigs. The effect of color on
the temperature of the twigs has been worked out by Whitten’ who
found as great as eight degrees centigrade difference between air
temperature and that of purple twigs in winter. He also found by
carefully sectioning buds that when the twigs are kept whitewashed
during the winter they do not push as rapidly during warm periods
as do buds on twigs not whitewashed, and in some springs, though
not in all springs, he was able to cause the blooming time to come
somewhat later. However, it would not be expected that such a
process would affect the blooming time as much as it affects the
amount of starting during warm days in early winter, since at bloom-
ing time the buds are for a good share of the time exposed to an opti-
mum temperature for growth or nearly so, and during warm days
in winter the air temperature is below the optimum temperature
for growth and often even below the minimum temperature. The
temperature of these winter twigs may be raised by absorbing sun-
light to at least above the minimum temperature for growth and in
some cases to the optimum temperature. Thus those who have
expected whitewashing to cause an appreciably later blooming in
spring would naturally, in many cases, be disappointed. In sec-
tions, however, where much killing occurs in winter following the
starting of buds by warm periods, it should be expected to give good
results.

While prolonging the rest period by causing growth late in win-
ter by the above method applies only to sections far enough south
that there would be a considerable number of warm days before the
rest period is entirely ended (sections like the southern half of Mis-
souri and farther south), the benefits from whitewashing would be
expected to be as great say in New York or Canada in March before
the optimum temperature for growth is reached as in Missouri, un-
less the sunlight should be less direct and there should be less in-
crease in twig temperature caused by the absorption of light by the
dark color. However, the cost of whitewashing an acre of trees,

‘Mo. Agr. Exp. Sta. Bul 38, 1897. (Bibl. No. 114.) Das Verhaltnis der Farbe, etc.,
1902 (Bibl. No. 116).
145

(even assuming that the cost of one of the sprayings could be deducted
since it could possibly be made to control either San Jose scale or
peach leaf curl), would be in the neighborhood of $10 or $15 an acre,
so before one would be justified in recommending such a method,
it should be tried under orchard conditions for a long enough term
of years to be sure that, say in twelve or fifteen years, enough peaches
would be saved to justify the expense. There would unquestionably
be some years when no benefit would be received in return for the
whitewashing.

Killing Temperature of Peach Blossoms. A considerable
amount of effort has been made to determine, under average condi-
tions, the temperature at which the blossoms of peaches are killed.
Unquestionably there is a considerable difference in the killing tem-
perature of bloom in different years. The killing temperatures in-
dicated by laboratory experiments will be given in the last part of
this paper (Table 51.) Here the temperature at which bloom and
young fruit has been killed in the orchard, and the condition which
favor the smallest amount of killing will be discussed. During the
spring of 1908 a freeze came on April 3rd when the temperature went
to 24° F. at Columbia. Phenological notes taken that spring show
that the first bloom on peach trees ranged from March 25th to March
30th, and full bloom ranged from April 5th to April 8th. The

following table gives the percentage of bloom killed by this freeze:

10
146

TABLE 46. SHOWING THE PERCENTAGE OF PEACH BLOoom KILLED
ON THE BASAL END AND THE OUTER END OF TWIGS BY THE
FREEZE OF APRIL 3, 1908, WHEN THE TEMPERATURE

WENT TO 24° F.

 

 

 

 
  
 

Basal half of twigs End half of twigs
Variety
Number | Percentage| Number | Percentage
Buds Killed Buds Killed

Oldmixon.............0e eee 159 70.44 363 84.39
Oldmixon.......... 2.0 e eee ee 426 11.03 598 41.97
Oldmixon..............2-0 00. 648 15.12 828 67.23
Blbertayg v5 ic cuies dod cgeaiw aden 374 19.78 | 603 44.92
Elberta ns wtaceiecgeaia ene egana sat 121 38. 205 69.2
Elbertace: oesats seve ease oe 163 52.1 143 71.3
Crawford’s Early............. 95 5.26 155 25.16
OPtig i 25205 Gaara vane  oat cas dais 623 46.70 553 55.50
Sre Odes arsuccssace ans: atdescaia ord geaneuavios 503 14.25 492 65.44
SEEM ah nysice ike ard eae ale ero 354 45.48 413 53.75
Sneed) csscveca vate wages 251 23.1 186 50.5
Kalamazoo..............0085 579 32.29 529 54,23
Family Favorite.............. 483 26.70 431 63.80
Family Favorite. ae 256 22.22 192 66.14
Golden Gate................. 129 85.2 72 50.
Dewey Cling................. 106 14.1 109 73.4
Dewey Cling.......... errs: 171 12.2 111 17.1
Elberta Seedling.............. 151 5.9 216 73.
Elberta Seedling.............. 1850 11. 980 16.3
Connetscaes tea eicea ices Heres 395 _ 11.1 507 43.1
Total No. buds............... 8367 lesceangien. 8257
Average percentage killed.....].......... Dil DAs | Vato wa aus anens 53.68

 

 

 

 

 

Of course many of these blooms were not yet fully open and
a much larger percentage of the flowers were fully open on the outer
half of the twigs than on the basal half, as the following table will
show:
TaBLE 47. SHOWING PERCENTAGE OF BLOOM FULLY OPEN ON THE
BasAL HALF AND THE OUTER HALF oF TwIcs
BY APRIL 4, 1908

 

 

 

Basal Half Outer half
Variety ;
Number | Percentage; Number | Percentage
Buds Unopened Buds Unopened
Elberta Seedling.............. 151 13.2 216 0.0
Elberta Seedling.............. 1850 22.7 980 60.2
COnnetasetiied 2 als cong ay oases 395 65.8 507 0.0
Sneed sci iideis gare igh re ne eaecs 174 16.0 252 0.4
Elbertay oscciw sive paces ce canes 251 6.7 186 0.0

 

 

 

 
147

Not nearly so large a percentage of unopened as open bloom
was killed, as the following table will show:

TABLE 48. SHOWING PERCENTAGE OF OPEN AND UNOPENED BLOOM
KILLED BY THE FREEZE OF ApRIL 4, 1908

 

 

 

Buds Open Buds Unopened
Variety ;
Number | Percentage} Number | Percentage
Buds Killed Buds Killed
Oldmixon Free............... 253 69.9 30 36.6
Oldmixon Free............... 326 25.4 241 15.3
Blbertascd cascte anes exes ove i 347 24.4 85 Tess
Elberta: ..%ccs0c0s00exenaewes 309 51.13 26 1.1

 

 

 

 

It will be seen that enough fully open bloom was uninjured
at this temperature, 24° F., for a good crop if the tree had a heavy
set of bloom. In fact a minimum thermometer that checked with
those of the U. S. Weather Bureau registered a temperature in the
Missouri Experiment Station orchard of 23° F., so in some years
at least, peach bloom may be expected to withstand a temperature
that low.

Those three tables bringing out the facts, that the bloom just
before the petals open will withstand lower temperatures than fully
open flowers; that the flowers open more rapidly toward the tips of
the twigs, and that therefore flowers on the outer half of the twigs
are less likely to survive a spring frost coming before the bloom is
fully open, suggest that the tree should be pruned to a sufficiently
open head that the leaves at the base of the twigs will not be shaded
off before fruit buds are formed.

The greater hardiness of unopened buds is apparently not due
to the protection of the petals. In freezing 59 unopened blooms
to a temperature of -3° C., 11.8 per cent of the pistils were killed
while of 50 unopened bloom with the petals and stamens removed,
no pistils were killed. ;

On April 30, 1908, the temperature fell to 28° F. in Columbia.
' The calyx tube was just breaking from the young fruit. The follow-
ing table gives the percentage of fruits killed at Columbia:
148

TABLE 49. SHOWING PERCENTAGE OF YOUNG FRUITS FROM WuaicH
THE CALYX TUBE HAs JusT FALLEN KILLED BY A
TEMPERATURE OF 28° F. Aprit 30, 1908

 

Number

n Percentage
Fruits

Variety bag!
ille

 

 

 

749
279
248
301
300
442
411
454

~T00 NbN
w

ANnWun NNO
COMODAWAUNY

 

_

 

It will be seen that large percentages of the fruits were killed
only on early varieties like Sneed and Alexander that had reached a
larger size. In the southern portion of Missouri where the fruit
was larger, more was killed than at Columbia, though the tempera-
ture was higher, Koshkonong reporting 32° F. Of course in the
lower land where most was killed, the temperature was naturally
lower. It is apparently certain then that under average seasonal
conditions, the older the fruit at the time of the freeze, the more
easily it kills. It is possible that this would not be true in years
when the bloom is pushed out very rapidly by exceptionally warm
weather and when continuous cool weather follows the setting of the
fruit. There is a rather general opinion that just when the calyx
tube falls, the fruit is left more susceptible to cold because it has lost
the insulation furnished by the calyx tube and requires time for ad-
justment. The fact that pistils of unopened flowers are not more
easily killed when the external flower parts are removed, and the fact
that buds of the peach were not more easily killed by freezing when
the scales were entirely removed, would indicate that with the slow
falling of the temperature that prevails under natural conditions, the
insulation amounts to but little. It seems certainly true, from the
experience of the season of 1908, that peach fruits are more tender a
week or more after the calyx falls than say one day after it falls.

In examining, the fruits that were killed in the southern portion
of the State in that year, in very many cases no injury was found
to the flesh of the fruit, but the seeds were killed. Where the rate
of fall of temperature is not too rapid under laboratory conditions,
it is generally the seeds that are killed at the highest temperature.
In fact from a large number of observations upon the results of
eeddds

149

freezing peaches in the laboratory, the tissue kills in the following
order, beginning with the most tender: the veins surrounding the
seed, the kernel, the flesh. When the peach has reached considera-
ble size, the woody covering surrounding the kernel is most hardy.

The greater tenderness of the seed may be accounted for by
the difference in sap density. Thus the freezing point depression
for the seed kernels, when they are large enough to separate from
the seed practically, was found to be 0.765° C., while that for the same
fruit with the kernels excluded was 1.075°.

At Koshkonong and at Goodman in 1908, following the freeze
of April 30th, the fruit was injured least on the young vigorously
growing trees. Thus at Koshkonong in the orchard of Mr. W. C.
Paynter, weak trees in various parts of the orchard and trees on
rocky, uncultivated portions had all the fruit killed, while vigorous
trees further down the hill where the temperature must have been
lower, as well as further up the hill, bore a full crop. In the case of
killing of buds in winter, whether they have been started into growth
or not, and in the case of killing of blossoms in spring in the southern
part of Missouri, in some years the Elberta is one of the most tender

- varieties. Yet where it is the young fruit that is killed, the Elberta

 

seems to be one of the most hardy varieties, at least other varieties
were killed to a larger extent than Elberta in that year. Early
varieties where the fruit was large at the time of the freeze uniformly
killed worse than later ones. In Missouri, at least, early varieties
do not bloom earlier than late varieties like Salway. In fact in ex-
treme South Missouri such early Chinese Cling varieties as Sneed,
Victor and Carman, on account of their longer rest period actually
bloom later than late varieties like Elberta or Crawford’s Late or
Heath Cling, yet from the time of pollination there is much more
rapid growth of the young fruit of the early varieties. Thus when
the calyx tube is dropping from the Elberta peaches, the young
Sneed will be much larger.

As to means of handling the trees to avoid injury at blooming
time or after fruit is set, there is not so much that can be done except
that, as mentioned above, in the most southern portions of the peach
belt it is possible, by increasing the vigor of the tree, to cause the

: blooming to be later and, therefore, the young fruit at any given time

after the bloom falls, to be smaller when the frost might come.
This, of course, would not apply further North. Vigorous, trees
may also have their fruit killed to a smaller extent because, in their
tendency to make wood growth, the fruit develops apparently more
slowly, at least fruit is practically always later in ripening on vig-
150

orous trees than on weakly growing trees. The whitewashing might
also in some years have some effect on the amount of killing at bloom-
ing time, though it would probably have very slight effect on the
amount of killing of young fruit after the bloom has fallen.

BREEDING VARIETIES HARDY UNDER SOUTH MISSOURI
CONDITIONS

The most important ultimate means of reducing the amount
of injury to both fruit buds and blossoms from low temperatures
is by plant breeding. From what has been said above, for this
southern region the varieties that would seem the most promising
to use in breeding for hardiness would be some of the Chinese Cling
group. With but few exceptions, the varieties of this group are
more hardy than the average peaches, not only for this southern
peach belt, but fortunately for the northern section also. Elberta,
however, is a marked exception. It may be said further that the
Chinese Cling comes nearly enough true to seed that it has been very
useful in securing new varieties with size and shippping qualities
desired. The quality, however, is rather low and the color poor so
it must be crossed with something that will give color,—preferably
yellow,—and quality. It seems highly probable that desirable
hardy varieties of long rest period could be secured by crossing this
strain with some high quality yellow fleshed peach like Fitzgerald,
etc. However, the Elberta, the most promising example of this
crossing, has certainly been a failure so far as hardiness is concerned.
The Gold Drop and Lemon Free, being peaches of yellow flesh, fair
quality and very hardy in bud for northern or southern climates,
and rather hardy in wood, is promising, though so far we have been
unable in the first cross to secure yellow flesh. The Hills Chili group
may be among the hardiest varieties in both wood and bud for south-
ern as well as for northern climates, but the quality is poor and re-
sistance to rot so slight that it is a question whether they will be de-
sirable for use in developing new hardy varieties for market condi-
tions. Reference to Table 41 will show that the Green Twig varie-
ties have as long rest periods as those of the Chinese Cling group.
In addition to this they are hardy because their pale color reflects
the sunlight instead of absorbing it;! yet their small size and indiffer-
ent quality, together with the fact that in all crosses with Purple
Twig varieties they have taken the typical purple color, would seem

1J. C. Whitten, Mo. Agr. Exp. Sta. Bul. 38, 1897. (Bibl. No. 114). J. C. Whitten, Das
Verhaltnis der Farbe, etc., 1902. (Bibl. No. 117).
151

to eliminate them as promising material for breeding hardy varieties
of desirable quality.

Hardiness of Seedlings. With reference to the opinion some
people have that seedlings are, for some unaccountable reason, more
hardy than budded fruits, it may be said that in the season of 1911
the Missouri Experiment Station was able to secure the percentage
of buds killed by two different freezes, one before any buds had
swelled and one after some swelling, from seedlings of a number of
common varieties, the most important being seedlings of Chinese
Cling, General Lee, Elberta and Family Favorite of the Chinese
Cling group, Lewis, Early Michigan and Hills Chili of the Hills
Chili group; and of the Snow, one of the hardy Green Twig varieties.
The following table gives the results:
152

TaBLE 50. SHOWING THE RELATIVE HARDINESS OF SEEDLINGS OF
VARIOUS VARIETIES OF PEACH AS INDICATED BY PERCENTAGE OF

Bups KILLED By A TEMPERATURE OF -8° F. JANuaARyY 5,
1911, AND BY A TEMPERATURE OF +6° F. FEB. 23, 1911.

 

 

Percentage | Percentage | Percentage

Number of of of Buds
Variety of Buds Buds Alive

Buds Killed Killed After Both

Jan. 5, 1911 | Feb. 23, 1911 Freezes
32 96.8 0.0 3.2
89 79.8 7.8 12.4
57 93. 5.4 1.6
100 96. 4, 0.0
133 66.9 9. 24.1
36 100. 0.0 0.0
107 80.4 12.2 7.4
72 41.7 51.4 6.9
103 77.6 16.6 5.8
110 79.1 17.3 3.6
60 °85. 13.5 1.5
28 96.4 0.0 3.6
44 88.7 2.3 10.0
60 66.3 20.0 13.7
100 84.0 10.0 6.0
38 78.9 2.6 18.5
52 71.1 9.6 19.3
54 98.2 1.8 0.0
94 61.7 8.5 29.8
9 100.0 0.0 0.0
55 81.8 10.9 73.0
26 88.4 11.6 0.0
66 75.7 18.2 5.1
63 46.0 33.4 20.6
52 94.2 5.8 0.0
90 75.5 18.1 6.4
75 73.3 8.0 18.7
136 69.8 13.3 16.9
58 60.3 37.9 1.8
80 41.2 20.0 38.8
112 63.4 25.0 11.6
101 = 7542 9.9 14.9
110 57.3 10.0 42.7
32 71.9 6.2 21.9
128 71.1 6.2 3.9
56 57.1 42.1 10.8
83 49.3 33.8 16.9
122 31.9 51.7 16.4
86 70.9 20.9 8.2
160 28.1 28.8 43.1
174 65.5 18.4 16.1
143 68.5 25.2 6.3
108 68.5 28.7 2.8
63 82.5 12.7 4.8
130 73.1 20.8 6.1
150 67.3 22.0 10.7
106 78.3 17.9 3.8

 

 

 

 

 
153

 

 

 

 

 

 

 

Percentage | Percentage | Percentage
. Number of of of Buds

Variety oO Buds ' Buds Alive

Buds Killed Killed After Both

Jan. 5, 1911 | Feb. 23,1911} Freezes

Thurber... svsevewwe 48 77.1 18.8 4.1
Thurber............. 118 84.7 13.6 1.7
Thurber............. 120 56.6 28.4 15.0
Thurber............. 78 97.4 2.6 0.0
Thurber sescivactiacc cones 188 75.0 22.3 2.7
Thurber............. 133 92.5 6.0 1.5
Thurber............. 134 70.9 15.6 3.5
Thurber a4 e204 + cas44 152 82.9 15.1 2.0
Family Favorite...... 116 82.7. 16.4 0.9
Family Favorite...... 106 75.4 14.2 10.4
Family Favorite...... 72 86.2 6.9 10.5
Family Favorite...... 86 74.4 15.1 10.5
Family Favorite...... 75 86.6 10.7 2.7
Family Favorite...... 108 59.3 32.4 8.3
Family Favorite...... 97 40.2 36.0 23.8
Family Favorite...... 107 74.8 15.9 9.3
Family Favorite...... 103 95.2 3.9 0.9
Family Favorite...... 100 94.0 3.0 3.0
Family Favorite...... 44 86.3 3.7 10.0
Family Favorite...... 185 48.1 44.3 7.6
Family Favorite...... 124 77.4 20.2 2.4
_ Family Favorite...... 98 79.5 19.4 1.1
':| Family Favorite...... 134 66.4 27.6 6.0
i: Family Favorite...... 122 72.9 24.6 2.5
-+: Family Favorite...... 91 84.6 12.1 3.3
|| Family Favorite...... 132 72.7 25.8 1.5
‘'' Family Favorite...... 142 64.8 34.4 0.8
Family Favorite...... 145 79.3 20.0 0.7
Family Favorite...... 161 45.3 38.5 17.0
Family Favorite...... 133 73.7 24.8 1.5
Family Favorite...... 101 92.2 5.9 1.9
Family Favorite...... 154 70.1 28.5 1.4
Family Favorite...... 107 79.4 18.7 1.9
Family Favorite...... 124 86.3 12.9 0.8
NOW sie: Gases daa 281 33.8 51.6 14.6
SMO Wiss ae cvese waxnie ans 170 32.4 61.7 5.9
SnOWSs wens eek ateeaes 290 34.5 58.6 6.9
Snowe neuer caiewecs 145 40.7 43.4 15.9
SNOW sos. ota ede sleey 265 35.6 57.8 6.6
SNOW): access oe ns oes 231 33.7 57.8 8.5
SNOW. cic dca ee 89 BRS 224 40.0 58.0 2.0
SHOW ils. vausienenr aes 232 43.5 54.3 2.2
Snows sais cas 298 25.1 61.4 13.5
Sno Wissen wae seers 226 28.7 60.0 11.3
Hills Chili..........- 161 74.5 24.9 0.6
Hills Chili........... 118 83.0 16.1 0.8
Hills Chili........... 77 79.2 19.5 1.3
Hills Chili........... 133 717.4 19.6 3.0
Hills Chili........... 153 67.3 32.0 0.7
Hills CHilf,..na940%s 105 50.4 44.7 14.9
Hills CHUM piano «ose 136 61.8 30.8 7.4
Hille: Chit crinnucexa ss 136 55.1 40.4 4.5
Hillis Chilis sinner aces 111 54.0 34.3 11.7
Hills Chili........... 135 57.0 31.1 11.9
184

 

 

 

Percentage | Percentage Percentage
Number of of Alive
Variety Buds Killed Killed After Both
Jan. 5, 1911 |Feb. 23, 1911 Freezes

Hills Chili........... 155 53.5 42.0 4.5
Hills Chili........... 154 55.2 36.3 8.5
Hills Chili........... 89 77.5, 20.2 3.5
Hills Chili........... 233 49.8 45.5 4.7
Hills Chili........... 127 51.1 44.2 4.7
Early Michigan...... 153 91.0 9.0 0.0
Early Michigan...... 181 47.0 26.5 26.5
Early Michigan...... 94 57.4 16.0 26.6
Early Michigan..... 3 93 48.3 42.0 9.7
Early Michigan...... 81 39.5 12.3 48.2
Early Michigan...... 86 55.8 32.5 11.7
Early Michigan...... 112 62.5 12.5 25.0
Early Michigan...... 67 43.2 38.8 18.0
Early Michigan...... 184 27.2 47.3 25.5
Early Michigan...... 71 40.8 23.9 35.3
Early Michigan...... 57 33.3 54.4 12.3
Early Michigan...... 81 61.6 29.6 ' 7.8
Early Michigan...... 74 37.8 35.1 27.1
Early Michigan...... 78 42.3 47.4 10.3
Early Michigan...... 75 90.6 8.0 8.6
Early Michigan...... 118 31.3 18.7 50.0
Early Michigan...... 63 50.8 39.7 9.5
Early Michigan...... 92 38.07 38.0 22.0
Early Michigan...... 94 57.0 38.3 4.7
LO WiSisse44-o6 sone tec 75 82.7 13.3 4.0
LG WiBis. sso. sees sites ce re 111 65.8 30.6 3.6
LeWI8iiiscissaanesads 115 40.9 31.3 27.8
Lewishesi. ace san eee 181 43.0 45.3 11.7
LéWisSis: s22 sede sues 152 51.9 38.2 9.9
LO WIS) oe b5hise hd are 132 73.5 19.7 6.8
Lewis): cess taco castles 124 62.1 29.0 8.9
General Lee......... 231 37.2 7.4 55.4
General Lee......... 130 50.0 16.1 30.0
General Lee......... 229 65.9 22.2 11.9
General Lee......... 153 73.2 22.2 4.6
General Lee... eis 139 35.2 30.9 23.9
General Lee... 100 47.0 30.0 23.0
General Lee... sacs 88 58.0 38.6 3.4
General Lee......... 109 86.2 9.2 4.0
General Lee......... 108 71.3 19.4 9.3
General Lee......... 108 38.9 40.7 20.4
General Lee......... 112 44.7 15.3 40.0
General Lee......... 170 22.4 40.0 37.6
General Lee......... 131 60.3 21.4 18.3
General Lee......... 115 63.4 15.7 20.9
General Lee......... 105 32.4 10.5 57.1
General Lee......... 101 39.6 17.8 42.6
General Lee......... 114 77.2 20.2 2.6
General Lee......... 109 75.3 12.8 11.9
General Lee......... 100 78.0 7.0 15.0
General Lee......... 102 50.0 28.5 21.5
General Lee......... 131 77.1 22.9 0.0
Chinese Cling........ 154 63.6 35.0 1.4
Chinese Cling........ 149 62.4 14.8 22.8

 

 

 

 
155

 

 

 

 

 

Percentage | Percentage Petcentaze
é Number of of Ali
Variety Buds Killed Killed | aster both
Jan. 5, 1911 |Feb. 23, 1911 Breezes
Chinese Cling........ 118 37.2 28.1 34.7
Chinese Cling........ 204 33.3 20.0 46.7
Chinese Cling........ 64 84.4 12.5 3.1
Chinese Cling........ 123 54.5 32.5 13.0
Chinese Cling........ 121 39.6 38.1 21.3
Chinese Cling........ 176 34.6 28.4 37.0
Chinese Cling........ 219 34.2 13.2 51.6
Elberta, averages sey ax sin qs0d a ved coed Said a een hdl wales alawos als 10.92
Thurber, average sce vs esa gia ccdca! esenore sveueu.e-u ws ele oituasy a qvaccuace waren 11.5
Family Favorite, average.......... 00. cece ccc cecccncceenvees 5.4
SNOW) AVETA GE eo secoc eich pale es aks ane 2 ace ew Lente eipsines aon een chars ae 8.7
Hills "Chil, Average oss soc sue as tosever tes-< seas gcbesa ccs: scour au and chien oa 8.3
Early Michigan, average..............0 cc cece eeeen eee eee eees 19.9
Lewis A Vera Gera waa epi Sea hangs Sb ao des seers ore eTee 10.4
Général: Wee, averages wectitc: huis gers vd we ee hi ee ee aes ee 21.6
Chinese Cling, average............ 000 cc cece eevee eeeeeeeeee 23.5

 

 

It should be said that the varieties of the Hills Chili group
are usually less vigorous growing trees, and since these seedlings were
very closely planted, trees of the Hills Chili group would suffer more
from shade in summer and thus have a larger percentage of buds
not fully developed that are killed during even a mild winter. It will
be seen that as a general thing those varieties which are most hardy
have given seedlings that are also most hardy. By referring to this
table and to Table 39 it will be seen also that these seedlings were
generally not more hardy than the parents, though of course in the
case of Elberta—a cross between the rather hardy Chinese Cling
and Crawford’s Early, and tender like Crawford’s Early—some of
the seedlings would tend to be more hardy than Elberta.

KILLING OF APPLES

Killing of the Roots. Killing of roots was not discussed for
peaches because so far as can be learned, the killing of peach roots
does not vary greatly from the killing of apple or of other fruit-tree
roots. The killing of apple roots is probably a more common phe-
nomenon than the killing of peach roots because peach roots are not
so much more tender than apple roots as peach wood or peach fruit
buds are more tender than apple wood or apple fruit buds. On ac-
count of the greater tenderness of wood and fruit buds, the peach tree
156

is not grown commercially in as severe climates as those in which
apples are sometimes grown, yet killing of roots of peach trees is
observed in fairly important commercial peach districts.

Macoun? reports that killing of apple roots is fairly common
in the northern portion of the apple growing section and says that
the root killing they have had in Canada has been when apples were
worked on seedlings of southern forms, and that since the crab has
been used as stock, the killing has been much less.

Emerson’ at the Nebraska Experiment Station planted apple
trees in boxes two feet square and eighteen inches deep, each box hav-
ing twenty-five young roots. The boxes were left out of doors
about the middle of December, the soil having different percentages
of moisture. The trees were examined on February 25. In an un-
protected box containing 10.4 per cent of moisture, twenty roots
were killed, only five remaining uninjured. Another unprotected
box containing 15.2 per cent of moisture had nineteen killed and six
injured. In a box containing 19.8 per cent of moisture, three were
killed, ten injured and twelve uninjured. A box covered with straw
mulch and containing 16 per cent of moisture had none of the roots
killed, and only seven injured. A box covered occasionally with snow
and containing 15.8 per cent of moisture had seven dead, eight in-
jured and ten uninjured. No roots were injured in a box stored in
a cool, dry cave, though it contained but 10 per cent of moisture.
It is shown from this experiment that the low moisture content in
itself did not do the harm, but the low moisture associated with low
temperature. It does not seem, however, that one is justified in
concluding, as Macoun apparently does, that plants at any given
temperature kill worse in media with as small as 10 per cent of mois-
ture than in media with 20 per cent of moisture. From experience
here it would seem likely that the reverse is true. Careful tempera-
ture records would probably indicate that the temperature was lower
in the boxes containing the smaller moisture content, and a dry soil
will freeze more deeply than will a moist soil. Thus a mulch or sod
or cover crop that tends to prevent evaporation from the soil will
prevent its freezing so deeply and thus prevent injury to the roots
by keeping the temperature higher.

Craig* studied root killing in Iowa for the winter of 1898-99.
The injury was worst in light dry soils not protected by a cover crop

i8tone, Mass. (Hatch) Exp. Sta. Rpt. 1911, p. 66. (Bibl. No. 107). Green, W. J. and
Ballou, F. H., Ohio Agr. Exp. Sta. Bul. 157, 1894. (Bibl. No. 48).

Canada Exp. Farms, Rpt. 1907-8, pp. 110-16. (Bibl. No. 68).

s’Nebraska Agr. Exp. Sta. Bul. 79, 1903. (Bibl. No. 33).

‘Iowa Agr. Exp. Sta. Bul. 44, 1900. (Bibl. No. 25).
157

In case of light soils like the “‘loess’”’ he found that deep planting
helps to reduce the danger from root killing. Such soils would of
course freeze more deeply and the temperature of the roots would
be lower. He had little opportunity to observe directly the differ-
ence in hardiness of different stocks, except in one case where Shield
Crab was used as stock, three-year nursery trees of Jonathan, Whit-
ney, Grimes and Willow came through the winter,in good condition,
though nursery trees generally were badly injured. In examining
injured trees he found that the stock at the union of stock and scion
was often killed while immediately adjoining scion tissue was
uninjured. He found scion roots to be more resistant than stock
roots. This is in accordance with experience here in freezing roots
in the laboratory. We have also found that the root system becomes
more tender as it gets further from the crown. Emerson and others
have observed that roots of trees are killed at a much higher tempera-
ture than are other tissues. This has been our experience. Results
with freezing roots of orchard trees will be found in Tables 30, 31,
32, 33, and 34.

In case of one-year-old roots of the French crab used asstock
by most of the nurserymen, about S° C. to -8° C. isas low a tempera-
ture as they can be depended upon to withstand with no injury.
Of 90 Jonathan apple grafts with French crab stock frozen toatempera-
ture of -9° C. or lower and then planted in soil in the greenhouse,
none lived. Four out of ten lived after being frozen to a tempera-
ture of -8° C.; three out of ten after a temperature of -7° C.; six out
of ten after a temperature of -6° C., and practically all grew after a

"temperature of -5° C. These roots had not been exposed to a high

temperature during the winter preceding the freezing, which was done
from March 2, to March 18, 1911.

According to Craig and also Stone, when the roots are frozen,
the results do not show to the inexperienced at once in spring. The
trees will often bloom and usually the leaves will partially expand
before the injury begins to show clearly. If only a part of the root
system is killed, only certain connected branches will show the effects
of the root killing.

Injury to Apple Wood. Macoun! lists a number of forms of
winter injury to wood of fruit trees, especially the apple, as follows:

Bark splitting, which he says usually occurs when growth has
continued late in autumn and an early summer has prevented the

soil from freezing.

1Canada Exp. Farms Rpt. 1907-8, pp. 110-16. (Bibl. No. 68).
158

Trunk-splitting, sun scald, a killing of the bark on the south
or southwest side of the tree which he reports very serious in north-
ern and eastern Ontario and in the Province of Quebec.

Killing-back which he says results from inherent tenderness
of the variety, or from insufficient maturity of the wood.

Crotch-injury, a killing of the cortex and perhaps other tissue
in crotches of the limbs. Macoun, Morse, and Grossenbacher have
studied this form of injury, and have found it to follow severe winters.
Macoun and Morse attribute this injury to the lodging of ice in the
crotch, while Grossenbacher attributes it to tearing caused by ten-
sions developed by the shrinking of the tissue during its frozen con-
dition. Grossenbacher observed this form of injury most commonly
in the crotch formed by vigorously growing secondary branches.

Black-heart, @ condition which follows the killing of the sap
wood when the cambium is left alive to form new wood outside the
killed area. It is troublesome to nurserymen in northern sections.

Trunk-injury or body injury, a killing of the older parts of the
tree above the snow line. Macoun thinks this injury may be due
to loss of water while the tree is frozen. Grossenbacher! describes
a similar injury as Crown Rot, and attributes it to tearing from ten-
sion in the tree when frozen, and to a loss of water while frozen.
He seemed to find it worse on the side of the tree trunk next to the
prevailing winds.

The experience of the Missouri Experiment Station where the
wood of the body of the tree, especially at the base of the tree trunk
and at the crotches, becomes hardy more slowly in autumn in some
years at least than does the tissue of the secondary branches or even
the twigs (see Table 24) may have some bearing in connection with
some of the above forms of injury, especially crotch injury and body
injury, or crown rot. It seems possible that those forms of injury
are merely direct freezing to death and that such injuries are more
commonly found at the base of the trunk, or at the crotch, because
on such years these are the most tender points.

Grossenbacher thawed the bark of a tree with warm water and
worked the tree backward and forward when the temperature was
-26° C. on January 8. In March practically all of the bark was found
to be dead, showing apparently the characteristic browning of direct
freezing to death. It would seem doubtful if this condition of com-
plete death of the tissue with the browning would be found so soon

1New York (Geneva) Agr. Exp. Sta. Tech. Bul. 23,1912. (Bibl. No. 50). New York
(Geneva) Agr. Exp. Sta. Tech. Bul. 12, 1909. (Bibl. No. 51).
159

if it were merely a mechanical injury such as tearing loose of the
bark. In this case it seems highly probable that the killing resulted
from rapid temperature fall. The thawed tissue would fall to the
temperature from which it was thawed, very rapidly, and from ex-
perience here with rapid freezing (see Table 20) it would seem proba-
ble that this tissue was killed by direct freezing the same as buds
would be on account of this rapid lowering of the temperature.

Sun scald is generally thought to result from the effects of the
heat gathered by the dark tissue that is in the direct sunlight. Since
Macoun reports sun scald as being serious in climates as far north
as the Province of Quebec, it would seem doubtful if there would
be enough heat gathered on the sunny side of a tree trunk in winter
there to raise the tissue to a temperature high enough for growth to
take place. From experience here where the raté of temperature
fall makes such a large difference in the killing, it seems highly prob-
able that, at least in northern sections, sun scald may not result
from the tissues starting into growth, but it more likely results from
the temperature being raised to near the freezing point on sunny
days during cold weather and dropping very rapidly to the tempera-
ture of the air as soon as the sun is off that part of the tree trunk.

As to varieties most hardy in wood under extreme conditions,
Macoun! reports an examination of about 700 varieties in which he
found that summer and fall apples were generally more hardy in wood
than late winter varieties, probably because their wood reaches a
condition of maturity earlier. In his experience some of the most
hardy varieties were: Canada Baldwin, Winter Rose, Ontario,
Stockton and McIntosh, all apples of northern origin. Oldenburg
was cited by him as being one of the hardiest in wood.

The group of apples which Hedrick lists as hardy for the coldest
part of the state of New York are: of summer apples, Yellow Trans-
parent, Tetofsky, Oldenburg, Red Astrachan, and Lowland Rasp-
berry; and of fall and winter apples, Wealthy, Hibernal, and Fa-
meuse groups. Among the varieties that would not withstand the
cold in the northern districts were: of summer apples, Early Harvest;
and of fall and winter apples, Baldwin, Black Gilliflower, Jonathan,
Rome, Winesap, and in the very coldest region, even the Northern
Spy group.

The Killing of Apple Buds. The buds of apples will withstand
much lower temperature than will the buds of peaches or of even
plums and cherries, and Macoun reports the killing of buds of apples

1Canada Exp. Frt. Farms, Rpt. 1906, pp. 291-92. (Bibl. No. 70).
160

even in a very dormant condition. Whipple! describes a considera-
ble amount of killing he has observed in Montana. When apple
buds are killed it is not necessarily true that all parts of the buds are
killed; generally only the flower parts, so that the buds will open
in the spring into a whorl of leaves and for this reason the fact that
any killing occurred may not be observed. He found also that in
some cases not even all the flower parts were killed, but on opening,
various malformations were to be observed; thus in some the pistils
were entirely absent and in some both stamens and pistils. In some
cases seedless apples were developed from such flowers.

Under Missouri conditions, especially in the Ozark region in
the thinner soil, we have observed a considerable amount of killing
by the freezes of December 9 and 29, 1909, when the temperature
went to -5° F. and -8° F. respectively. During the same year buds
of the York Imperial, as well as Jonathan, that had been largely
killed by the same freeze, were sent in from points in Illinois. In
most cases, however, the entire bud was killed. The Jonathan is
the one variety in which a considerable amount of such injury has
been observed. In low places where the cold air may settle and re-
sult in a very low temperature, all of the Jonathan buds were killed,
even on healthy trees. However, in the Missouri Experiment Sta-
tion orchard following a temperature of -20° F. on January 7, 1912
not a large percentage of the buds were killed. Of 200 Jonathan
buds counted, 38 per cent were found to have been killed, and of
the same number of Ben Davis buds counted, none were found dead.
Of course some buds in which the flower parts were injured may have
been overlooked. However, a good crop was secured in that year.
In this orchard the trees had been kept in a healthy condition, while
practically all the orchards observed, and all the orchards from which
twigs were sent, were neglected orchards where the trees had made a
weak growth the summer before and had set their fruit buds very
early, probably pushing them too far early in the season before this
freeze.

Killing of Apple Bloom. Killing of the flowers is a common
form of injury to apples resulting from low temperatures, at least
under Missouri conditions. An effort was made to determine what
is approximately the killing temperature of the full bloom of apples.
The following table gives the results of freezings with apple, peach
and other fruits, just before the bloom opens, in full bloom, just after
the bloom falls, and when the fruit is as large as it has been when it

1Montana Agr. Exp. Sta. Bul. 91, 1912. (Bibl. No. 113).
was killed in Missouri.
mum for thirty minutes.

161

could be made with the freezer used.

The material was generally kept at the mini-
The temperature fall was as slow as it

 

 

 

 

 

 

 

TABLE 51. GrtvING RESULTS OF ARTIFICIAL FREEZING OF FRUIT
BLossoms
; Condition of Tem-| Num- |Percent-
Material Flowers When Date pera- ber age
Frozen ture |Blossoms| Killed
Apple, Ben Davis...... Not fully openjApr. 14,’11) 27.5 87 31.0
Peach, Elberta Seedling] Fully open..../Apr. 14,’11) 27.5 66 6.1
Pear, Kieffer.......... Fully open...../Apr. 14,'11] 27.5 40 0.0
Plum, Wild Goose......} Fully open..../Apr. 14,’11) 27.5 60 0.0
CREPE Yssiis 9 aris versa ee sine sis Not fully open|Apr. 14,’11) 27.5 97 50.5
Apple, Stannard....... Fully open..../Apr. 15,’11] 27.5 45 40.0
Peach, Elberta Seedling] Fully open..../Apr. 15,’11] 27.5 87 60.9
Pear, Kieffer.......... Fully open....|/Apr. 15,’11) 27.5 70 32.8
Plum, Wild Goose......] Fully open....|Apr. 15,’11) 27.5 50 0.0
Cherrysi.c.acnneay saais Fully open....jApr. 15,11) 27.5 91 58.2
Apple, Ben Davis...... Fully open... .|Apr. 15,11} 27.5 61 22.9
Peach, Rareripe........| Petals falling..)Apr. 28,’13) 26.6 86 25
Apple, Jonathan........] Not fully open|/Apr. 28,'13) 26.6 100 8.0
Apple, Jonathan....... Fully open....|/Apr. 28,’13| 26.6 78 56.4
Apple, Jonathan....... Petals falling..|;Apr. 28,'13) 26.6 120 18.0
‘Cherry, English Morello| Fully open... .|Apr. 28,’13) 26.6 130 48.5
uCherry, English Morello] Petals falling..)Apr. 28,’13) 26.6 107 67.1
Apple, Rome Beauty...| Fully open....)May 1,’13) 24.8 83 40.9
‘Peach, Hiley.......... Young fruit...|May 1,'13|) 24.8 76 1.3
Cherry, Montmorency..| Fully open....|May 1,'13) 24.8 40 52.5
Apple, Jonathan....... Young fruit....|May 10,13] 26.6 53 71.7
Peach, Early Bernard. .| Young fruit...)May 10,13) 26.6 74 94.6
Peach, Gold Drop...... Young fruit...|May 10,13) 26.6 65 75.4
Cherry, Dyehouse...... Young fruit...|May 10,'13) 26.6 44 70.4
Plum, Wild Goose......| Young fruit...|May 10,'13) 26.6 93 16.1
Pear, Kieffer.......... Young fruit...]May 10,'13) 26.6 32 78.1
Apple, Jonathan....... Young fruit...|May 17,'13) 24.8 19 68.4
.Peach, Lewis.......... Young fruit...|May 17,'13) 24.8 23 43.5
: Cherry, Dyehouse...... Young fruit...|May 17,'13] 24.8 15 66.6
oie

 

These artificial freezings are not accurate in determining the
minimum temperature which the bloom, etc., will withstand, since
it is not possible to duplicate in the freezer the rate of temperature
fall, etc., outside, nor is it possible to make two freezings exactly
However, it is safe to conclude from this
table that the unopened flowers are slightly more hardy than the
fully open ones, and that the fruits are slightly more tender than the
flowers. The difference with apples, judging from these freezings
and from our observations on freezings outside, is not so great as

‘duplicate each other.

with peaches.
11
162

These results indicate that peaches, either in blossom or young
fruit, will withstand slightly lower temperatures than will apples.
The greater hardiness of the peach bloom is probably under-empha-
sized in this table. In the year 1911 the Elberta Seedling peach tree
came into full bloom on April 12, while the Ben Davis apple came
into full bloom on April 18 to 22, and the Stannard apple on April
20. It is almost certain then that the peach blossoms listed as fully
open were older than the apple blossoms so listed and had been pol-
linated and had started rapid growth, while the apples had not. In
1913 the Early Bernard peach came into full bloom on April 11, and
the Hiley and Rareripe on April 16-17, while Jonathan apple came
into full bloom April 24, and the Rome on April 29. Here then the
young fruits of the peach were older than were the young apple fruits
used. From results of freezes as seen in the orchard, we are con-
vinced that at times, at least, bloom and young fruit of peaches will
withstand lower temperatures than will apple bloom or young fruit.

The freeze of April 30, 1908, when the temperature in Columbia
went to 28° F., killed only the percentages of young peach fruit
shown in Table 49, and an excellent crop was secured from the peach
trees the summer of 1908, while practically all the apple fruit was
killed; yet the peach fruit had been set longer. The peach trees in
that year came into full bloom from April 5 to 7, while varieties of
apples like Ben Davis, Jonathan and Grimes, fruit of which was
all killed in this orchard, came into bloom from April 15 to 17. The
Ingram apple in that year came into full bloom on April 22 to 24
and had some bloom left when the freeze came. It had a fair crop
of apples left, and the Ralls, which came into full bloom from April
23 to 25 and had a considerable amount of open bloom when the
freeze came, had very few fruits or blooms killed. If peach blooms
or fruits are more often killed in spring than that of the apple, it is
because peaches usually bloom considerably earlier.

In avoiding a loss from low temperatures in spring, the most
important factor is late blooming. Some varieties like Ingram and
Ralls bloom so much later than ordinary varieties that, except in
very few sections of the State, they are practically never killed by
spring frosts. Other varieties that apparently are seldom killed
under Missouri conditions are Benoni and Mother, according to in-
formation furnished by Mr. F. W. Faurot, formerly of the Missouri
State Fruit Experiment Station at Mountain Grove, Missouri.
Growers in southern Illinois also report Benoni as being rather safe
from frosts. Rome Beauty on many years blooms enough later than
other varieties to escape injury. Whether in the southern portion
163

of the apple growing region this blooming in spring can be caused
to be delayed by prolonging the rest period, as in the case of peaches,
has not been studied. Mr. Faurot however, tells of an instance in
which cultivated trees were three days later in coming into bloom
than uncultivated trees of the same variety, with like treatment in
every other way. The fact that the buds on well kept Jonathan
orchards on good soil were not killed to such a large extent by the
freezes of December, 1909, as were the buds on trees in neglected
orchards that had gone dormant much earlier the season before,
seems to indicate that the buds in early winter, at least, are kept
dormant later by keeping the tree vigorous.

An opinion is held by some fruit growers and horticulturists
that if the tree is in a vigorous condition the bloom or young fruit
will withstand lower temperatures because of the healthier condi-
tion of the bloom or young fruit. Three Gano apple trees on the
Station grounds have been left unsprayed and uncultivated and are
in a weak condition, one of them in a very weak condition. At
times bloom or young fruit from these have been frozen along with
bloom or young fruit from well kept Gano trees. These weak trees
and the vigorous trees in Columbia bloomed at the same time. The
. following table gives the results:

TABLE 52. SHOWING RELATIVE HARDINESS OF BLOOM AND FRUIT
From WEAK AND From Vicorous GANo APPLE TREES

 

 

 

 

 

 

Tem-| Num- |Percent-
Material Date pera- ber age
ture | Frozen | Killed
Vigorous sprayed tree................. May 1,’12} -3 28 71.4
Weak unsprayed tree.............044. May 1312 -3 16 87.5
, Vigorous sprayed tree...............-. May 1,712 -5 50 100.0
Weak unsprayed tree.............-0-- May 1,'12 -5 40 95.0
Vigorous sprayed tree..............-.-- May 4,'12 -2 52 21.1
Weak unsprayed tree.............---- May 4,'12 -2 56 19.7
Very weak unsprayed tree............. May 4,’12) -2 46 32.6
_ Vigorous sprayed tree ,
* (fruit 3g in. in ee ach Wve. Waals Mens sueonaeteae May 18,’12| -4 98 81.9
ery weak unsprayed tree :
(fruit 4 in. in dia.).............006- May 18,’12} -4 79 83.5

 

It will thus be seen that there is no constant difference in the
hardiness of the fruit from the weak and the vigorous tree. Casual
observers may mistake loss of crop from cool weather at blooming
164

time, poor pollination, or other reasons, for injury from freezing.
It is certainly true that a poor set of fruit is often attributed to frosts
when a careful observation following the frost would have shown
that no bloom or fruits were killed.

KILLING OF CHERRIES AND PLUMS

Killing of various tissues of other fruits has not been extensively
studied at this Station, except as described in the early part of this
paper. As to killing of buds, Macoun! states that under Canadian
conditions, especially in the Province of Quebec when away from the
protection of a body of open water, European and Japanese plums,
and cherries are injured more or less every winter. He lists Mount
Royal and Raynes as new varieties very hardy in bud. Japanese
plum fruit buds have killed in Missouri only after cold -periods fol-
lowing sufficient warm weather to start them into growth.

In case of killing by spring freezes, the Wild Goose plum is very
resistant to low temperature as will be seen by reference to Table 51.
On April 24, 1910, when all other fruits in the Station orchard, ex-
cept Ingram and Ralls apples which were just in bloom, were
killed by a temperature of 27° F. Wild Goose plums were uninjured
though they had reached a diameter of 3-16 of aninch. We are not
prepared to say, however, that the young fruit of the Wild Goose
plum is not more hardy than the bloom.

In the case of cherries observations have been made on the kill-
ing of the Early Richmond cherry buds to a large extent, and other
varieties to a small extent, especially by cold periods following warm
weather. On January 7, 1912, the following percentages of fully
dormant cherry buds were killed by a temperature of -20° F.: Early
Richmond, of 200 buds counted, 52.5 per cent were killed; Mont-
morency, of 150 buds counted, 12 per cent were killed; Dyehouse,
of 175 buds counted, 11.4 per cent’ were killed.

Macoun holds that fruit buds of cherry, peach and Japanese
and European plum kill more easily than do the buds of the apple
and the pear because they have less protection from evaporation.
Goff? found a larger percentage of cherry buds to survive a tempera-
ture of -27}4° F. in Wisconsin in February, 1899, in the central por-
tion of the tree than on the ends of the outer branches. He concludes
that this results because those near the center of the tree were par-
tially protected from drying winds. It does not seem probable

1Canada Exp. Farms, Rpt. 1907-8, pp. 110-16. (Bibl. No. 68).
216th An. Rpt. Wis. Agr. Exp. Sta. pp. 283-88, 1899. (Bibl.{No. 46).
165

that evaporation affects the killing of buds unless it be indirectly
by the drying out of the twigs. Cherry buds are more tender than
apple buds when exposed to sudden freezes like that at Columbia,
Missouri, January 7, 1912. They are also more tender when frozen
in the laboratory under conditions such that buds with the scales
removed kill no worse than normal buds. Evaporation could cer-
tainly play no part there. The buds at the ends of peach twigs are
generally more tender than those near the base of the twigs or on
spurs along the branches, but buds on the ends of twigs down in the
tree are as tender as any. It is probable that the buds that Goff
found more hardy toward the center of the tree were formed earlier
in summer and were more mature when the freeze came.

One of the most promising means of avoiding loss from low
temperatures is by orchard heating, burning oil, coal or other material.
In some sections this practice is followed profitably, and it is recom-
mended in others. This subject is being studied at the Missouri
Experiment Station by Dr. W. L. Howard. In the work here re-
ported, no data has been gathered that is of value in a study of or-
chard heating, unless the results with freezing bloom and young
fruit may be of some value in determining the temperature at which
heaters should be lighted. Data on the killing temperature of the
bloom of fruit to be protected is very essential in orchard heating,
otherwise the heaters will too often be lighted and large expense
incurred when it is unnecessary, or perhaps sometimes they may not
be lighted when it is necessary, and loss will be incurred. A study
of orchard heating, like a study of the value of whitewashing as a
means of preventing killing from cold, should be carried on through
a large number of years since heating involves an expense certainly
not less than an average of $10 or $12 per acre a year, besidesalarge
initial investment, and the mere fact that the crop can be saved by
heating is no positive indication that in a period of twelve or fifteen
years enough crops will be saved, in spite of accidents inherent in
the method of heating, to pay for the cost of heating.

ACKNOWLEDGEMENTS

This work was begun under the direction of Dr. J. C. Whitten
of the Department of Horticulture of the Missouri Agricultural Exper-
iment Station, and advice has been received from him throughout
the work. Advice has also been received from Professor W. L.
Howard of the Department of Horticulture, Professors B. M. Duggar,
C. Stuart Gager, and G. M. Reed of the Department of Botany;
166

and Dr. Hermann Schlundt of the Department of Chemistry of the
University of Missouri has been repeatedly called upon for informa-
tion where the work in this bulletin required knowledge of physical
chemistry. Mr. A. J. Heinicke and other advanced students, who
have from time to time been connected with the Department, have
assisted in the laboratory in securing the data here published. All
chemical analyses have been made under the direction of Professor
P. F. Trowbridge of the Department of Agricultural Chemistry.

Professor U. P. Hedrick of the Geneva, New York, Experiment
Station and Professor H. P. Stuckey of the Georgia Agricultural
Experiment Station, furnished twigs used in some of the freezings
reported in this bulletin. Professor Hedrick and also Professor
R. A. Emerson of Lincoln, Nebraska, were kind enough to furnish
publications that were not available here, as well as repeatedly to
give advice.

Grateful acknowledgment is made to these men and to others
. mentioned in this bulletin who have been kind enough to furnish in-
. formation.
~

Oo 2 AD WR YH

11.
12.

13.
14,

15.
16.
17.

18.
19.
20.
21.

SN, 22 :

T

23.
24,

167

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Waite M. Be Deut Trees Frozen in 1904. U. S. Dept. Agr. B. P. I. Bul.

» PP. ate

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WE Ne Winter Protection of the Peach. Mo. Agr. Exp. Sta. Bul.

‘ ;

Whitten, J. C., Pruning Peach Trees. Mo. Agr. Exp. Sta. Bul. 55, 1902.

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1912.

Winkler, H., Ueber den Einfluss der Aussenbedingungen auf die Kalte-
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Woodbury, C. G. and Wellington, J. W., Orchard Heating. Purdue Agr.
Exp. Sta. Bul. 154.
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CHART SHOWING MAXIMUM AND MINIMUM TEMPERATURE CURVES AT COLUMBIA AND KOSHKONONG DURING THE YEARS 1901 TO 1912

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