ALBERT R. MANN
LIBRARY
AT
CORNELL UNIVERSITYCornell University Library
QK 926.P18
Flower ecology
3 1924 001 762
31924001762487Flower Ecology
^ v? by 2,^
L. Hi PAMMEL.
Press of J. B. Hungerford.This book is dedicated to my parents, as an
for what they have done for me.
appreciation
«■

TABLE OF CONTENTS.
CHAPTER I.
Flower Ecology:	History 1,/pollination and fertiliza-
tion, adaptations for sexual reproduction, conditions op-
posed to self-fertilization 2, self-fertilization, methods of
bringing fertilizing bodies together 5.
CHAPTER II.
Hydrophilous: Eel grass 7, lemna 8, water weed 9.
CHAPTER III.
Anemophilous:	Grasses, lodicules 12, time of opening
of flowers 13, corn, wheat 15, tall meadow oat grass 17,
woody plants, hazel 17, pine 18, alder 19, aquatic plants,
herbaceous plants 20.
chapter iv.
Entomophilous 21, bees 22, butterflies and moths 26,
flies and beetles 28,' reasons for attraction, modes of attrac-
tion 30, attraction of insects 31, color variations 34, odors
of flowers 37.
chapter v.
Special Adaptations:	Ranuncnlaceae 40, Berberid-
aceae 41, Funiariaceae 42, Cruciferae 43, Yiolaceae 44, Cary-
ophyllaceae 44, Geraniaceae 46, Vitac’eae, Leguminosae 47,
Jfosaceae 55, Saxifragaceae 59, Lythraceae 60, Onagraceae
62, Cucurbitaceae 64, Umbelliferae 66, Caprifoliaceae 67,
pompositae 68, Lobeliaceae 73, Campanulaceae, Ericaceae
74, Primulaceae 75, Oleaceae 77, Asclepiadaceae 78, Gentia-naceae 80, Polemoniaceae, Borraginaceae 81, Convolvulaceae
82, Solanaceae 83, Scrophulariaceae 84, Labiateae 87, Aristo-
lochiaceae 92, Elaeagnaceae 93, Urticaceae 94, Salicaceae 96,
Orchidaceae 97, Iridaceae 107, Liliaceae 108, Araceae 113,
CHAPTER VI.
Flowers and their unbidden guests:	Perforation of
flowers 116, How flowers are protected 117.
CHAPTER VII.
Cross and Self-Feriilization of Plants:	Cross-fertili-
zation 121, impotency 127, cucurbits 129, pears 130, superi-
ority of crossed plants, 131, self-pollination 132, cleistoga-
mous flowers 133, Autogamy and Alpine plants, Autogamy
in grasses 135, Cause for cleistogamy 136.
CHAPTER VIII.
The effect of cross-fertilization in plants 139.
CHAPTER IX.
Hybrids 146, parental characters 147, rose hybrids 150,
Apples 151, cucurbits 152, ternary hybrids 153, graft hy-
brids 154, prepotency 153.WORKS OF,REFERENCE.
Sprengel—Das endeokte geheimniss, der natur im bau und der befruchtung
der blumen. Berlin, 1793.
Gray * structural botany, p. 215.
MacLeod—Lijst von Boeken, Verhandelingeri, enz omtrent de bevruchting
der bloemen, von 3883 to 18PS verschenen. Botanisch Jaarboek, tweeds jaargang
1890. Kruidkundig genootschopte Dodonaea te Gent.
H. Mueller—Die befruchtung der blumen durch insekten. Leipzig, 1873.
English translation by D’arcy W. Thompson, London. 1883. Die alpenblumen,
ihre befruchtung durch insekten, und ihre anpassung an dieselben. Leipzig,
1881, etc,, etc.
Fritz Mueller—Flowers and insects. Nature, Vol. XVII, p. 78, 1878. Two
kinds of stamens with different function in the same flower. Nature, Vol.
XXVII, p. 364,1883, etc., etc.
Axell—Om anordningarna for fanerogama vaxternas b efruktning, Stock-
holm. 1869, etc., etc.
Hildebrand—Ueber die befruchtung der salbeiarten durch insekten. Bonn,
Sitzber. Niederrheimgesellsch, pp 54-56, 1864.
On the impregnation of orchids as a proof of the two different effects of
pollen. Ann. and Magazine of Nat. Hist., Series 3, Vol. XII, pp. 169-174, 1863.
Die geschlechter vertheilung bei den pflanzen. pp. 92. Leipzig, 1867.
John Lubbock—On British wild flowers considered in relation to insects.
London, 1875.
Scientific lectures (Lecture I, flowers and insects). London, 1879.
Grant Allen—The colors of flowers as illustrated by the British flora Na-
ture, Vol. XXVI, pp. 299, 323, 346, 371. London, 1882.
Delpino—Ulteriori osservazioni sulla dichogamia nel regno vegetable Milan.
Part 1,1868,1869; Part II fasc. I, 1870; fasc. II, 1875.
A. Kerner—Die schuetzmittel der bluethen gegen unberufene gaeste. Vien-
na, 1876. Translated by Dr. Wm. <~>gle, “flowers and their unbidden guests.”
London, 1878.
Pflanzenleben. Vol. II, p. 91-447. Engl. Translation, Oliver Natural His-
tory of Plants.
Forbes—Selective discrimination of insects. Nature. Vol. XVII, p. 62, 1878.
Bennett-^Insects and Flowers. Popular Science Review, Vol. XIV, pp. 113-
125,1875.
Francis Darwin—Bees visiting flowers, papilionaceae. Nature, Vol. IX, p.
189,1874.
Alpine flowers, a review of Hermann Mueller’s alpenblumen. Nature,
Vol. XXIII, p. 333, 1881.Charles Darwin—Fertilization of orchids. London, 186*3.
The effects of cross and self-fertilization in the vegetable kingdom. Lon-
don, 1876.
The different forms of flowers on plants of the same species, etc.
Loew—Beitraege zur Kenntniss der Bestaubungs einrichtungen einiger
lubiaten with two Plates. Ber. d. deut. bot Gesellsch. Berlin, Vol. IV, 1886,
pp. 113-143, plates V and VI, etc.
Zur Biologie der Apccyneen Bot. Centralblatt, Vol. VII, No. 45,1881.
Ueber die biologischen eigenthumlichkeiten der plantagineen. Bot. Cen-
tralblatt, No. 39, 1880, etc,; Pflanzenbiologie.
Asa Gray—Structural botany, Nbw York and Chicago, 1879.
How plants behave, New York, 1872.
Cleistogamous flowers in exybaphus nyctaginea. Am. Naturalist. Vol. VII,
p 692, 1873
Cros9-ferliiization of scrophularia nodosa. Journal of Botany, Vol. IX, p.
375, 1871, etc.
W. Trelease—Nectar, what it is and some of its uses. Report upon cotton
insects. By Henry Comstock, Washington, 1879.
On the structure which favors cross-fertilization in several plants. Pro-
ceedings Boston Foe. of Nat. Hist , Vol. XXI, 1883, Mch. 15.
The nectary of yucca. Bull. Torrey Bot. Club, New York, 1836, p. 135, Rep
Mo Bot. Garden, etc.
Charles Robertson—Note on the mode of pollination of asclepias. Bot. Ga-
zette Vol. XII. 1887, p. 288.
Flowers and insects. Bot. Gazette Vol, XIV, p. 120, etc. Am. Nat. Vol.
XXIX, p. 97.
Trans. Acad, of Sci. St. Louis, Vol. VI. No 14, etc., etc.
C. V. Riley Observations on the fertilization of yucca and on the structural
and anatomical peculiarities in pronuba and prodaxus. Am. Naturalists, Vol.
XVII, 1883, p. 197.
. On the oviposition of the yucca moth. Transaction of St Louis Acad, of Sci.,
St Louis, Vol. Ill, No. 2, p 208. See also Vol. Ill, p. 568, etc. Rep. Missouri Bot.
Garden, 1892.
Foerste—The fertilization of the wild bean (phaseolus diversifolius) Am.
Naturalist, Vol. XIX, p. 887. 1885. Notes on structure adapted to cross-fertiliza-
tion with plate. Bot. Gazette, Vol. XIII, 1£81, p. 151. The nectar glands of
apios t uberosa. Bull. Torrey Bot. ( lub, Vol XI, p. 123, 1884, etc. Sensitive
stigmas as an aid to the cross-fertilization of flowers. Proc. Am. Ass. Adv. of
Sci. (Buffalo) 1876, p. 286, etc.
C. M. Weed—Ten New England blossoms and their insect vis tors.PREFACE.
It has always seemed desirable to me to give some in-
struction along ecological lines in a general course in botany.
Ecology considers the external relations of plants, and no
field offers greater opportunities to awaken an interest in
botany than the relations existing between flowers and in-
sects and other agents in bringing about pollination.
Much of the material contained in the following pages
has appeared before in some lectures delivered at the meet-
ings of the horticultural societies of this state. I have how-
ever added considerable new material. I have made free
use of published papers on the subject, especially those of
Robertson, Mueller, Ludwig, Trelease, Gray, Riley, Bailey,
Kerner and others, full credit has been given in the proper
places. I am also under obligations to Mr. C. R. Ball who
has assisted me in various wavs as well as Mr. Combs;
Mr. E. D. Ball who made some of the insects determinations
for me, and some help from Prof. H. Osborn and Mr. W.
Newell. To all I wish to express my sincere thanks.CHAPTER I.
FLOWER ECOLOGY.
Few questions buve attracted greater and more attention
than the adaption to secure cross fertilization. Aside from
the interest scientists take in this question, it has a practical
hearing on horticultural and agricultural problems. When
we remember that horticulturists are turning their attention
to the improvement of our native fruits by cross fertilization
and hybridization, we must accord to this subject a prom-
inent place.
Insects have played a very important part in rendering
flowers attractive. It is well known that many plants can-
not produce seed unless an^ insect or some other agent con-
veys the pollen from anther to stigma.
It is interesting to follow the history of this
History. pjiage b0tany. It is now one hundred years
since the foundation of this study was laid. The keen
and sharp observer, Christian Conrad Sprengel, published
a remarkable book on the structure of flowers and their
relation to insects, although he made some observations as
early as 1787. In speaking of the hairs on the corolla of a
Geranium he says:	“The wise Author of Nature would not
have created even a hair in vain.” Earlier than this Koel-
reuter saw the necessity of insect visitors to some flowers.
Sprengel surmised that these hairs served to protect the
honey from rain. This work was almost lost sight of till
the brilliant mind of DarwiD saw the full import of Spren-gel’s observations. Darwin’s work “On the Fertilization of
Orchids,’’ published in 1862, gave an impetus to the study
which has continued till the present time. D’Aarcy W.
Thompson in 1883 gives the titles of 814 papers; J. Mac-
Leod, 638 papers from 1883 to 1890.
Among the numerous workers in this line I can only
mention a few:	Hermann Mueller, Fritz Mueller, Axell,
Hildebrand, Lubbock, Grant Allen, Delpino, Kerner,
von Marilaun, Forbes, Bennett, Darwin, Loew and Lud-
wig. In our own country:	Gray, Trelease, Riley, Foerste
and Beal, Weed. The work of Mr. Charles Robertson, of Oarl-
inville, Illinois, deserves, special mention. He has done an
enormous amount of careful and conscientious work. No
other American botanist has collected such valuable data.
Those interested in this subject should consult these papers.
At the out set it is well to have a clear
understanding of what is meant by pollin-
ation and fertilization. Pollination is
simply the conveying of pollen from the anther to the
stigma. Fertilization occurs after the pollen has reached the
stigma; it is the impregnation of the ovule. Fertilization
has been defined as the union of protoplasm of two different
cells.
. .	. ...	.	In most higher plants both kinds
Adaptatibns for	"	1
.	of organs occur in the same flower,'
Sexual Reproduction.	°
so that it is possible to have close
fertilization—autogamous;—or from flower to flower in the
same plant—geitonogamous. But the rule is to be cross fer-
tilized —xenogamous.
Conditions opposed
To Self Fertilization.
Pollination and
Fertilization.
Dioecious. Stamens and pistils oc-
cur on different individuals, as in
willow.3
Trioeciovs. Staminate, pistillate, and hermaphrodite
flowers on different branches, as in ash.
Monoecious. Staminate and pistillate flowers separ-
ated but on the same plant, as in corn, melon, Oak. etc.
FIG 1.
Fi^- 1. Eel grass (Vallisneria spiralis)a. pistillate flower; b. male flower;
c. floating-staminate flowers with pollen. (After Lubbock).
Gynodioecious. Som& plants produce hermaphrodite
flowers, others only pistils without stamens, as in thyme.
Andromonoecious. Some plants produce hermaphro-4
elite flowers, others only stamens, as in buckeye.
Dichogamous. Stamens and pistils mature at different
times.
Proterandrous:	Stamens mature before pistil, as in
sunflower. -
Proterogynous:	Pistil matures before stamens, as in
Plantain.
Heterodichogamous:	Occurence of two kinds of plants
of the same species—some proterandrous, others protero-
gynous.
FIG. 2.
Fig, 2. Flowers of VaUisneria spiralis on the surface of the water, The float-
ing staminate flowers; one has come in contact with the stigmas. (After Ker-
ner von Marilaun).
Diptopogamous. Stamens and pistils in the same plant
but at different heights. Stamens on other individuals cor-
responding in heights to pistils and vice versa:
Heterodistybus:	Occurence of two kinds of plants,
some plants having long stamens and a short style and
others having short stamens and a long style, as in primrose.5
Heterotristylous:	Some plants having a long style
and stamens of l>oth short and of medium length in the same
flower; a second kind having long stamens and stamens of
medium length and a short style; a third plant has short
and long stamens and a pistil of medium length correspond-
ing to those of medium length stamens, as in oxalis,
la Plants.
K Methods of Bringing
Fertilizing Bodies Together.
lythrum, etc.
Autarigynous. Self sterile plants. The pollen of a
flower or of a plant will not fertilize the ovule of that plant.
Cases numerous, clover, calamus, etc.
Seif Fertilization Cleistogamous. Flowers do not open
as in the flowers of some Violets, Dead
Nettle and some grasses.
Delpino has made two divis-
ions:
(1.) Zoogamous, in which
fertilizing bodies move of their own accord. In lower
plants, algae, some fungi, etc.
I. Diamesogamous, in which movement is brought
about by some foreign agent. We are concerned here with
those of our second division. The agents may be arranged
as follows:
1.	Hydrophilous. Pollination is brought about by
the water.
2.	Anemophilous. Wind is the agent.
3.	Zoidiophilous. Pollination is brought about by
animals.
a.	Ornithophilous. Pollination is brought about by
birds that look for insects or nectar.
b.	Entomophilous. Pollination brought about by
insects.
1. Melittophllous. large bees.6
2.	Micromelittophilous, small bees and other insects.
3.	Miophilous, flies (Diptera).
4.	Micromiophilous, small diptera.
5.	Sapromyophilous, carrion flies.
6.	Cantharophilous, beetles, (Cleoptera).
7.	Psycophilous, butterflies, (Lepidoptera).
8.	Spingophilous, moths and sphin.
c. Malacophilous. Snails,CHAPTER II.
HYDROPHILOUS.
Few flowers are pollinated by water.
_ , „ Vallisneria spiralis is an excellent illustration.
Eel Grass	r
It is a commonplant found in ponds and
slow running streams in many parts of the eastern
United States.- It is stemless, bearing linear, thin,
ribbon-like leaves. The flowers are dioecious. The
FIG. 3.
Fig. 3. Duckweed (Lemna minor). 1, plant with only one pistil mature: 2,
the same with the first stamen mature: 3, both stamens mature, magniged six
times; 4, a fully developed flower magnified twenty-five times. (After Trelease.)
pistillate flowers are solitary and borne on long, slender
threads, which bring it to the surface of the water. The
flower consists of a perianth composed of three petals and
three small sepals. The three large stigmas are two-lobed
and are so situated in the mature flowers that they turn back
beyond the three petals; hence it is important that the sepals
should be small. The staminate flowers are numerous and8
crowded in a head at the bottom. When nearly mature the
staminate flowers break away from the plant and come to
the surface of the water, on which they float. In this con-
dition it forms a ball, but when fully mature the petals turn
back, forming a skiff like arrangement, the stamens length-
en out and the anther cells open. Each anther contians
thirty eight large, more or less viscid, pollen grains. The
three skiff like sepals are admirably adopted to float on
water. Short waves or currents of wind drive them along
until they come against a solid object, where they remain,
and if it be a pistillate flower the stamens come in contact
with it, leaving the pollen attached to the stigmas. After
fertilization the threads that bear the fertile flowers coil up
spirally, drawing the fruit under water, to ripen.
Lemma. Species of duckweeds are admirably adapted
to water pollination. The following account of pollination
of Lema minor is based on the observations made by
Trelease. Duckweeds are among the smallest of flowering
plants and form scums on the surface of ponds and slow
running streams in summer. They are very simple in their
structure. Each fertile found produces a single flower from
a cleft in the margin. The flower consists of a single pistil
and two stamens and a subtending bract. When the flower
expands, the pistil elongates sufficiently to expose about half
its length beyond the tips of the marginal fissure of the
frond. The stigma becomes moist by the exudation of a
fluid; and is now receptive. In this condition it remains
some days when the stamen furthest from the base of the
frond becomes exserted, attaining the length of the pistil
when it dehisces, the pollen remaining heaped in the open
cells of the anther. The second stamen dehisces several
days later. The flowers are therefore strongly proterogyn-FIG. 4.
Fig-. 4. (Potamngeton crispvs)—Staminate flowers with debisceing anthers
shown on the left. Pistillate flowers with large viscid stigmas on the right.
(After Kerner vob Marilaum.)
Another interesting plant pollinated by
Water Weed. wat.er E\0dea canadensis commonly found
in slow running streams and ponds northern United States.
9
ous. “Surface currants due to the wind, or other causes
crowd the plantlets together in masses in which the relations
of the several individuals are incessantly changing.” The
receptive stigmas must be pushed against the Older anthers,
through which tiny are pollinated. While there is in this
case an admirable adaptation for cross pollination, self- fer-
tilization may result when the pollen of the older stamen
drops on the stigma.Fig. 4 (Indian Corn, Zea mays.)—A pistillate spike. B, pistillate flowers with
envelopes. J, same showing long silken thread. B-o, Staminate flowers with
loosely hanging stamens (from Hackel.)11
It has also attracted codsiderable attention in Europe from the
fact that it has become a vertiable nuisance in choking canals
and streams. The plant bears three kinds of flowers: Stamin-
ate, hermaphrodite and pistillate. But all of these forms
apparently never appear together. Staminate and pistillate
occurring together. The fertile flowers are born on a long
tube which in most cases comes to the surface of the water
where it expands. The staminate flowers are attached at the
bottom; they break off as in Yallisneria, come to the surface
and float on the water. When fully mature they expand
and shed their pollen around the stigmas. Several other
plants especially the Asiatic Vallisneria alternifolia and the
tropical African Lagarosiphon are pollinated in a similar way.CHAPTER Ilf.
ANEMOPHILOUS. V1
The flowers in this class are usually dull in color, con-
tain no nectar; the sexes are often separated, i. e , they occur
in different flowers, one flower staminate, the other pistillate.
Both kinds of flowers are either on the same plant, when
they are said to be monoecious, or when one plant bears
either staminate or pistillate flowers it is said to be dioecious.
In wind pollinated flowers the anthers are borne in such a
way that the slightest breeze will cause the pollen to be
shaken out. The anthers always contaiu an abundance of
pollen. The pollen graina are light, not viscid, and easily
carried by the wind.
Grasses These important plants, numerous in species,
are almost exclusively pollinated by the wind.
The flowers are usually hermaphrodite, some monoecious and
some dioecious. In quite a number there is a difference in
the time of maturing of stamens and pistil.
Lodicules. Many of the flowers of grasses have a pair of
small scales (lodicules). They are close together, and the
bases are somewhat grown together. Hackel says. “The
rapid swelling of the bases, at least, causes the separation of
the flowering glume and palea, and consequently the opening
of the flower.” In grasses where these scales swell but little,
the flowers do not open very far. When they are absent the
spikelets are closed at the sides and the stamens and pistil
only protrude at the apex. These scales are very turgid at
the time of flowering.13
Time of Opening of Flowers. It is well known that tem-
perture and moisture greatly inflnence the opening of flow-
ers. Rains and lows temperature may retard the opening
Fig. 5. Tall meadow oat grass, (Arrhenatherum elatius). Wind pollinated,
showing how anthers open and the long plumose stigmas protruded. 1, Closed
anther. 2, An opened anther. 3, Parts of the pistil separated. 4, The effect
wind has on the flowers. (After Kerner von Marilaun.)
not only hours, but days. Dry air and a high temperature
also retards opening. The flowers of grasses open early in14
Fig. 6. Filbert (Corylus aveUana) showing fruits to the left and large stami-
nate catkins and the short axillary branches with pistillate flowers to the right.
The stigmas are red. (After Kerner von Marilaun],15
the morning:, usually when there is some dew on the grass.
Mr. F. A. Sirrine found about Ames that flowers usually
open between 5 and 9 a. m.
The flowers of Festuca elatior open before' 7 a. in.,
Andropogon provincialis before 7 a. m. Some, however,
open between 5 and 7 p. m. Kerner Marilaun states 4 to 5
a. m. foriPoa and Koeleria, 5 to 6 a. m. for Brizn media
and wheat (Triticum), 7 to 8 a. m. for oats (Avena) and
timothy (Phleum), 11 a. m. Agrostis, 4 p. m. Agropgron
Holcus opens its flowers twice during the day—at 6 a. m. and
7 p. m.
Cora As a rule the flowers of corn are fo ind in separate
parts of the plant; the staminate spibelets, collec-
tively called the tassel, are at the extremity, the pistillate
flowers in the axils of the leaves; the sexes are therefore sep-
arated (monoecious). Each staminate flower contains three
stamens. When ripe they hang loosely from the flower.
Each kernel (ovule) has coming from it a long silken thread
which is hairy, and when ripe somewhat viscid. The pollen
shakes out easily, as every one knows who has walked through
a cornfield and found pollen on his clothes. The flowers are
proterogynous.
The flowers of corn develop a certain amount of odor,
which is plainly perceptible at some distance. The flowers
are frequently visited by honey bees and other insects, chiefly
in quest of pollen.
Wheat w^iea*: the anthers and stigmas mature at the
same time, but the flowers are only partially
opened for about fifteen minutes. When the flowers open
the pollen is scattered, some of which remains within the
flower. Cross-pollination is brought about by the wind.
Delpino states that the flowers may be self-fertilized and good
seed produced.Fig. 7. Dwarf Mountain Pine (Pinus pumilio).—1 Staminate flower. 2 Section
through three staminate flowers. 3 Two staminate catkins more magnified, f'"
Branch containing staminate flowers from which the pollen has fallen, and a
pistillate cone on the right hand branch. 5 pistillate flowers. (After Kerner
vnn Mnrilmin17
Tail Meadow Oat-Grass.
The versatile anthers are borne on
long filaments and are set in
motion by the slightes breeze, which causes the pollen to be
shaken out in clouds. The stigmas are long and plumose
and readily catch the pollen. As in corn, the flowers are
proterogynous and by the time pollen is mature the stigmas
are withered.
A large number of our woody plants are
Woody Plants. p0]]jnatecj by the wind—the hazel, birch,
pine, cottonwood, oak, elm, etc.
Hazel our own Hazel (Corylus Americana Walt.) the
staminate catkins are pendent, the pistils occur in
short erect cones quite inconspicuous, the stigmas are red A
great abundance of pollen is produced. Our Hazel flowers
in early April. In the European hazel nut (Corylus avellana)
the istaminate flowers are borne in drooping cylindrical cat-
kins, each flower containing eight stamens with short fila-
ments. The anthers contain an abundance of pollen. The
pistilate flowers are not conspicuous, several occurring in a
scaly bud. The stigmas are of reddish color and large.
Many wind pollinated flowers have red stigmas
but these	are	to be explained	on physiological
grounds.	The flowers	may be	proterandrous or
proterogynous. As a general rule, in wind pollinated trees
bloom before the leaves are out, because the leaves interfere
with the distribution of pollen. As Robertson says:
“In the case of the wind pollinated trees it is obvious that if
the leaves were developed before the flowers, the process of
pollination would be greatly impeded by the leaves interfer-
ing with the free circulation of the wind and catching the
pollen which is intended for the stigmas.”Pitie.
18
The staminate flowers occur at the base of the
shoot of the same sprig. The fertile catkins occur
below the terminal bud or on the lateral young shoots. The
FIG. 9.
Fig. 9. (Pollen grains) 1 Cobaea scandens. 2 Mnrinia persica. 3 Cucurbiia pepo.
4 Passiflora kermesina. 5 Circaea alpinu. 0 Convolvulus sepium. 7 Cannabis
sativa. 8 Pinus pumilio. 9 Mimulus mnschatus. 10 Albucca minor, round grains
moistened, the others dry. 11 Dianthns Carthusianorum. 12 Corydalis lutea. 13
Oentiana rhaetica. 14 Salvia glutinosa. (After Kerner von Marilaun.
stamens open outwardly. The slightest jar on a tree will
cause a shower of pollen to issue. The structure of the pol-19
len grains is such that it is easily carried by the wind. It
consists of three cells, one of which only is fertile. The
others serve to buoy the pollen and therefore make it of easy
transport. The pistillate flowers are colored red, and have a
large receptive surface.
Pollen of conifers has been carried for more than a hun-
dred miles. The so-called “showers of sulphur” on ponds
consist of pollen grains which were suspended in the air
and brought down during a shower of rain.
Alder The a^er> which is a common plant in Eastern States
and Northeastern Iowa, bears itsstamine flowers in
long festoons. The pistillate catkins are more or less erect.
Fig-. 10. 1-2 Rhododendron hirsutum. 4 Epilobium angustifolium. (After Ker-
ner von Marilaun.)
Usually self-pollination is not prevented in the cultivated
European species, nor in some of our wild species.
John H. Lovell states the Alnus incana is partially dioecious.
Honey bees occasionally visit the stamine flowers for pollen.20
Aquatic Plants. A(luatic plants are also pollinated by the
wind, as Potamogeton crispus L., a plant
growing in ponds and slow running streams. While its
leaves are immersed in water the flowers are produced above.
The reddish brown stigmas mature before the anthers of the
same flower are open, but when the stigmas are wilting then
the perianth of the flower opens, the anthers mature,
when the wind blows over the water it carries the pollen with
it. Some of it is wasted, but a part of it is almost certain to
come in contact with the stigmas of younger flowers.
Plantain:	Common plantain occurs
in all of our door yards and who has
not observed the long, slender spike. The flowers are pro-
terogynous, the slender style shows before the stamens, when
the stamens appear the style is withered. The pollen must
therefore move upward. Anemophilous herbaceous plants
occur in widely separated orders, as Meadow Rue (Ranuncuz
laceae), Ragweed (Compositae), Hemp (Urticaceae), etc.
Herbaceous Plants.CHAPTER IV.
ENTOMOPHILOU8.
Anton Kerner, in that delightfully written work on the
Natural History of Plants, says, “If, however, mere casual
observation of the relation between flowers and their insect
visitors is sufficient to cause aesthetic pleasure, and has stimu-
lated people of every age and nationality to the production
of works of art, it may be imagined how great must be the
incentive to scientific study supplied by a deeper insight into
these phenomena, and what extreme pleasure is derived from
the successful discovery of the reasons for these wonderful
relations, and from tracing their connection with other facts
of science.”
^Zoologists believe that the bodies of insects are devel-
oped for the special purpose of visiting certain flowers. It
is equally true that flowers are correlated with the shape and
habits of insects that visit these flowers. These insects vary
from the small thrips, scarcely more than 1 mm. long, to our
largest butterflies and the still larger ones of the tropics,
whose expanded wings measure 15 cm. across. As such dif-
ferences occur in the insect world, so too there is a great
diversity among the flowers in odor and color. Beginning
with the early spring flowers to those of late autumn there is
a constant connection with the varied forms of insect lifeTJ
In order to fully understand the wonderful adaptations
between insects and flowers it will be necessary to consider
the structure of certain parts of insects. Insects have been
divided up into several orders. In point of importance they22
may be arranged as follows:	Hymenoptera Lepridoptera, Dip-
tera, Coleoptera, Hemiptera, Orthoptera and Neuroptera. In
pollination the last three may be excluded.
/>e most important pollinators in the order Hymenoptera
are honey-bees, bumble-bees, wasps, Halictus, Andrena and
Anthophora. The mouth parts of bees are especially con-
F1G. 11.
Fig. 11.—Left hand figue, head of Bombus aororum 9 with mouth parts separ-
ated, magnified five times. Right hand figure that of hive-bee in the same
position seen from below, magnified twelve times; pi labial palpi modified into
a tongue sheath, y submentum (fulcrum,) zz, retractors, i. e. those ehitinous
pieces which unite the submentum with the ends of the cardines, and as they
revolve backwards round the ends of the cardines, retract the mentum and its
appendages, li ligula, pm maxillary palpi, md mandibles, o eyes, Ibr labrum, la
lamina. (After Hermann Mueller.)
structed for the purpose of collecting nectar. The mouth23
parts of an insect consist of an upper lip, an under lip, a pair
of anterior jaws or mandibles, and a pair of maxillae. The
lower lip and maxillae are each provided with a pair of feel-
ers or palpi. The mandibles are usually hard and horny,
while the maxillte are delicate and membranous. Different
insects show great variation in the structure of their mouth
parts, even in the same order. Take members of the genus
Prosopis which construct their cells in sand and dry sticks,
the lower lip is constructed in the form of a trowel. This
insect has in fact no special adaptation for collecting nectar.
Although these bees feed their young on honey and pollen,
they can only obtain nectar in flowers with shallow nectaries.
In different bees there are various gradations, as in Andrena,
Halictus and Chelostoina. The lower lip becomes variously
, elongated until it reaches the length and form found in hive-
bees and bumble-bees which enables them to extract honey
from irregular flowers with deep seated nectar.
In Bombus the mouth parts consist of pa, the paraglossa,
li, the ligula, pi, labial palpi, pm, maxillary palpi, la, lamina,
mt, mentum, st, stipes, md, mandibles, and o, eyes. When
the mouth parts are fully extended and separated it seems
hardly possible that this large and complex apparatus for
sucking, exceeding in length that of the head, can be
received in the cavity below the head, but such is the case.
When a bee is sucking honey just within its reach, the car-
dines, the chitinous retractors just at the base of the mentum,
the laminse, labial palpi and tongue are fully extended. As
soon as the whorls of hairs at the point of the tongue are wet
with honey, the bee by rotating the retractors (below the sub-
mentum) draws back the mentum and with it the tongue, so
far that the laminse now reach as far forward as the labial
palpi. The laminse and labial palpi now lie close upon the24
tongue, overlapping at their edge form a tube, of which only
a small portion protrudes. At the same time the bee draws
back the basal part of its tongue into the hollow end of the
fig. n A.
Pig-. 11 A. Hind legs of bees, showing structures for collecting pollen, begin-
ning from the left. Hairy bee (Anthopohora retusa) four times enlarged. Bum-
ble bee (Bitmbus terrestris) four times enlarged. Honey bee (ApU mellifica) five
times enlarged, r trochanter, s femur, t tibia, a prickles on tibia, p tarsus
(pollonbrush). f other segments of the foot, k claws. (After Behrens.)
mentum and so draws the tip of the tongue moist with honey
into the tube where the honey is sucked in by the sucking
stomach. In flowers with shallow nectaries the bee need not
rotate the retractors. The tongue is therefore constantly
encased by the laminoe and labial palpi.
When a bee flies from one flower to another it carries the
proboscis extended so as to introduce it, in the act of alight-
ing, into the tube of the flower. The tongue is, however,
concealed within its sheath, to protect the delicate whorls of
hairs. Bees also have certain parts specialized for the collec-
tion of pollen, y)In some bees this is collected on the lower
posterior surface of the body; in others it is collected on thesur-
;.25
legs) In Megachile, where it is collected on the ventral
face, “the abdomen is furnished with long, stiff retroverted
hairs, by means of which the pollen is brushed from the
anthers as the insect passes in or out of the flower.” The
pollen grains are afterwards dislodged by means of its legs.
These insects can therefore readily get the pollen from
flowers with flat corollas. In Anthophora the pollen is col-
lected by the tibia and tarsus. They are broad and flat and
thickly covered with hairs. The pollen is brushed from the
anther by means of the hairs on the tarsus, and later is trans-
ferred to the tibia. In Bombus t'errestris the tibia is smooth
on the outer surface; the inner is covered with long, stiff
hairs, which with the tibia, form a little depression; into this
the pollen is brushed by the short hairs of the tarsus. In the
honey bee the arrangements are similar, except more perfect
FIG. 12.
for collecting pollen from the anthers. There are eight or
nine rows of hairs. The pollen from the anthers is trans-
ferred to the surface of the tibia or hairs, to which it readily
adheres. Behrens says:	“After the process of collecting
has been carried on for some time, the pollen forms in thick
yellow masses, which completely envelop the legs. Laden
with the fruits of its toil, the insect wings its way home-
ward and deposits them in the bee-hive.”Butterflies and Moths.
26
It lias been said that if Jthe chief
divisions of insects are to be ar-
ranged in the order of their importance as pollinators of our
native flowers, the first place must be given to bees (Hymen-
/
FIG. 13.
optera), while the butterflies and
moths (Lepidoptera) take only the
second or third place, before or after
the flies (Diptera). But if the ar-
rangement is based on the degree of
adaptation to flowers, Lepidoptera
undoubtedly take the first place, as
it is the only order which through-
out, and not only in certain of its
families, is fitted for obtaining
honev. In the perfect state, butter-
flies, so far as they take food at all, which is not the case in
all species, restrict themselves almost entirely to honey, and
since they take no further thought for their young than to
lay their eggs sufficiently concealed upon the food plant,
their mouth parts have been quite free to adapt themselves
to the easy obtaining of honey from various flowers. This
adaptation is attained by the great development of the max-
illary laminae with a suppression of the greater part of the
remainder of the mouth organs. The labrum and mandibles
FIG. 13 A.
Fig. 13 A. A butterfly
resting on a cluster of
flowers Natural size. (Af-
ter Behrens.)27
are aborted. The laminae of the maxillas are transformed
into two immensely long, hollow, rounded filaments provided
with semi-circular grooves on their inner surfaces, thus
forming a tube when placed in close apposition. In a state
of rest this tube is spirally coiled and concealed between the
labial palpi. This account of the insects is mainly taken
from Mueller’s work. The chief pollinators of the Lepidop-
tera are the butterflies, moths and hawk-moths. The butter-
FIG H
flies are diurnal visitors, and when on the wing flutter to and
fro; when on the flower their wings are folded back. (Fig.
13 A). The moths and hawk-moths are nocturnal visitors.
Moths do not take a position like butterflies when collecting
honey, but hover over the flowers with their wings in rapid
motion. Some of the Sphingidae or hawk-moths have very
long tongues. A species found in Brazil has a tongue
between ten and eleven inches long. In the United States28
and Mexico some of the hawk-moths have tongues several
inches long.
Flies and Beetles.
So far as diet and visitation are con-
cerned the flies are very important in
the pollination of flowers. The most important are drone
and syrphus flies. Many of these species depend on nectar
FIG 15.
Fig. 15. Flies. Beginning from the left, bumble-bee liy (Bombyltus major).
natural size. Empis llvida, 4 times enlarged. Syrphus fly (Syrphus). (From
Behrens’ text book).
and pollen. Their adaptations are such as to allow them to
collect honey and pollen. Rhingia and Eristalis have acorn-
plicated mouth structure. The bee-flies (Bombylius) are also
provided with a complicated sucking apparatus. (Fig. 15).
In flying they carry their probosces forward and ready for
action. They have the power of detecting concealed nectar
in flowers in a most marked degree. Thrips enter all sorts
of flowers, which they are enabled to do on account of their
small size. They feed on both pollen and honey. (Figs. 12
and 13).
Beetles in some cases show adaptations to utilize nectar
and pollen, but there is a very marked difference in species
and sub-orders. “None of our native plants,” says Herman
Mueller, “are fertilized exclusively or mainly by Coleoptera."
The large genus Meligethes, w7hich are small insects and can
creep into most flowers, is of much importance in pollinat-
ing flowers. In flowers where the honey is exposed (Cornus,29
etc.) many species of beetles lick the honey. In flowers like
Plantain (Phntago) where the honey is concealed, beetles
feed upon pollen. (See figure 16). Tropical and sub-trop-
ical beetles have in some cases excellent adaptations to obtain
FIG. 16
Fig. 16. Beetles—I to the left, Cerncnma schaefferi, natural size. II head ten
times enlarged. (I and IIo) Longicorn beetles. I Pachyta octnmaculata 3 times
enlarged. II ab Leptura livida. (After Mueller and Behrens’ from Behrens’
text book of botany).
nectar. Fritz Mueller observed a species of Nemognatha
sucking the flowers of Convolvulus in Brazil. The maxilla;
when opposed form a tube like the proboscis of a butterfly,
which is, however, not capable of being rolled up.
Why do insects go to flowers and
Reasons for Attraction. ...	.	•
of what advantage is it to the
plant? Insects go to the flower because it offers food, nec-
tar, pollen, or other substance. The insect must care and
provide for its young. Plants would not long provide this
food without some advantage accruing to them, hence we
have reciprocal adaptations. Note as an illustration the
adaptation in sage, clover, etc., or in certain nocturnal Lcp-
idoptera that lay their eggs in the flowers of some pinks, as
Soapwort. The larvae after hatching, feed on the young
ovules and seeds. When mature they bite a hole through
the side wall of the ovary and escape. These insects do not30
require all of the ovules. Shelter is another reason why
insects go to flowers, as in Indian Turnip, Skunk Cabbage,
e	f
The structures that attract insects
Modes of Attraction.	,	„	,	,
are, (1) large size, form, color, and
odor of flowers, (2) food (pollen, nectar), material for the
construction of nests, shelter as in Arum and Indian Turnip,
places where the eggs hatch and later the larvae feed on the
ovules, as in Yucca, etc.
Certain insects are excluded because of the color and
odor of flowers.
Herman Mueller classified flowers, with reference to
their insect visitors, as follows:
Pollen Flowers. Furnish insects with pollen only,
Poppy, etc.
Flowers with Exposed Nectaries. Adapted to various
kinds of insects, nectary shallow, not highly colored, yellow,
white, etc.,—Galium, Elder.
Flowers with Half Hidden Nectaries. Honey visible
during warm sunshine, number of visitors reduced, long
tongued insects have increased,—Cruciferae, Ranunculus,
Fragaria.
Flowers with Concealed Nectaries. Special adaptation
to a particular class of insects not developed. Short
tongued insects debarred, as in Mentha, Oxalis, Geranium.
Flowers in Heads, Nectar Concealed. Flowers rendered
attractive because of the massing,—Composites, Scabiosa.
Bee Flowers. Adopted to Hymenoptera. Short
tongued insects excluded,—Gentian, Digitalis, Columbine.
Lepidoptera Flowers. Nectar deep seated, in tubes,
spurs can be reached only by the long tongues of these
insects. Flowers fragrant. Diurnal flowers as Silene and31
Lychnis; nocturnal as in Saponaria officinalis and Nicotiana
affinis, etc.
Carriou Flowers. Dull in color, yellow, brown, dis-
agreeable urinary or carrion-like odor. Stapelia, Crataegus,
Smilax herbacea.
Deceptive Flowers. Insects (flies) attracted by false
nectaries. (Parnassia).
After having briefly considered the
Attraction of Insects. ,	„ .	.	.	,
structure ot insects it is now in order
to take up the attractive features of flowers. I think no one
can doubt that bright colors assist greatly in attracting in-
sects. Not all insect pollinated flowers are of bright color.
Many flowers that are pollinated at night are white, as in -
PIG. 17.
Fig-. 17. Neotaries. I. Buttercup {Ranunculus acris); II. longitudinal section;
III. Yellow Hattie (Uhinanthus); IV. Umbellifer (Anthriscus sylvestris); V.
Monk’s hood (Aconitum napeUun); III. three times enlarged; II. eight times
enlarged; IV. six times enlarged; V. natural size. n. nectary; b. petal; t.
nectar; f, k, ovary. (After Behrens.)
Datura and Nicotiana. Some night pollinated flowers are
pink and other colors, as in Phlox paniculata.
Grant Allen says:	“We can hardly resist the inference
that the colored whorls represent an intensification of the
natural tint in growing shoots and floral organs, slowly modi-
fied by the selective action of the in sect eye.” “Mueller, who
has carefully noted flowers and their insect visitors, observed32
31 distinct visitors upon the purple colored flowers of Malva
sylvest is and only four on the small white flowered Malva
rotund folia, Heracleum spondylium 118, Aegapodium podagra-
aria 104, Anthriscus sylvestris 73, Daucus carota 61, Cnicus ar-
vensis 88, Centaurea jacea 48, Tanacetum vulgare28. He says
although it is impossible in statistical tables to take into ac-
count the various conditions which may modify the visits of
insects, the general law holds good that the more conspicuous
flowers are visited more frequently than others.
Mr. Robertsou well shows that:	“Concealment of nec-
tar, however, accomplishes one important result that cannot
be accomplished by a change in time of blooming, and that
is the simultaneous exclusion of flies and sliort-tongued hyin-
enoptera. The effect of concealment of nectar can only be
ascertained by comparison with a form having free honey,
and blooming at the same time with Eryngium and Cicuta.”
The first condition which seems to be a departure from
the original type readily to induce departures of a more seri-
ous nature is an aggregation of flowers in a more or less
close cluster. In this case the lower lip loses its distinctive
function both as a vexillary organ and as a landing place.
Both offices are immediately assumed by the inflorescence
itself. ^As long as the flowers remain separate, they attract
the insects which are pleased by the special floral form and
are adapted to it. But when the flowers become clustered
they attract less specialized insects to what appears an undif-
ferentiated color mass. In a similar way, separated flowers
are only readily visited by insects to which the lower lip
forms a convenient resting place. But when the flowers
form a compact inflorescence, a landing place is formed by
the flower cluster. Even when the floral Structure remainsthe same, I always expect to find less specialized insects on
the crowded flower.”
£jhe relation between conspicuousness and pollination of
flowers is noticeable in some flowers, as in Lysimachia vul-
garis of which two forms occur, one in which the parts of the
flower are larger and colored more intense; in this case self-
pollination rarely occurs; but a form which grows in shaded
places has smaller and less conspicuous flowers and these are
seldom visited by insectgjC. An equally instructive lesson is
afforded by the small heart’s ease (Viola tricolor). The
PIG. 18.
Fig, 18. Nectaries. I. to the left, Hellebore (Hellebnms viridis). II. Colum-
bine (Aquilegia vulgaris). III. Yiolet (Viola odorata). I. and II. three times en-
larged. I. to the right, Parnassus (Parna88ia jjalustris). «. nectary, n. portion
where nectar is secreted ; f. stamen, b petal.
species has two varieties. The large flowered variety with
conspicuous flowers, variety vulgaris, which has given rise to
our pansy, is frequently visited by bumble-bees and other
insects. In fact there is no occasion for self-pollination since
insects carry pollen from one flower to another. The variety
arvensis on the other hand is smaller and is a weed in gardens
and fields. It is seldom visited by insects. Yet in both
cases the spur of the lower petal contains the honey. Rhin-
anthus crista galli variety major is abundantly visited by
insects while the vartety minor is not. It follows from this
that colors are important in pollination^734
Color Variations Changes in colors of different species
must be of advantage. Take a meadow
in which here and there occur groups of yellow flowered
meadow parsnip .(Zizia), a little distance away is the
scarlet painted cup (Castilleia coccinea). In late summer the
white flowers of spotted cow-bane (Cicuta virosa variety ma-
culata) a group of yellow flowered goldenrod (Solidage Mis-
souriens’s) are contrasted and the wild yellow lily (Lilium
panadense) is wholly unlike the purple fringed orchis (Haben-
aria psycoa.es). The change in colors is often conspicuous in
closely related species, especially in some highly modified
flowers like Phlomis, L nnium, Salvia, Delphinium, Aquilegia
and Aconitum; these species usually bear violet, blue, pink or
purple flowers. But when these are visited by the same
class of insects and growing in close proximity some of the
species have a different color, otherwise the end desired
would not be reached. ‘“Our species of	show this
color range beautifully. M. didyma is bright red; M. fsitu-
losa is rose color varying to white; M. Bradhuriana is pale
FIG. 19.
Pig. 19. Guides to honey. I. Pansy (Viola tricolor). II. Carthusian Pink
(Dianthus cartusianorum). III. Wound-wort (Stachys palustris). IV. Field
pink (Dianthus deltoides). [After Behrens ]
purplish white; M. Punctata is yellowish.” Some of our
violets are blue, some are white, others yellow. The cardin-
al flower (Lobelia cardinalis) is bright cardinal; great lobelia35
{Lobelia syphilitica), blue. It is true that these flowers do not
always occur in the same place, yet, in some cases they are
adapted to the same general class of visitors and it must be
of some advantage to have a contrast in colors. It is note-
worthy also that some species under different conditions show
changes in the color of flowers. Kerner von Marilaun cites
a species of Campanula (C. trachelium) which has white flow-
ers in the neighborhood of Brenners, Austria, but in the val-
leys of the limestone Alps the flowers are blue The alpine
flora of the Rocky Mountains is remarkable in showing
changes in the colors of flowers from one altitude to another.
The genus Delphinium is remarkable in showiug color
variations. A large larkspur, common everywhere in Iowa,
is described as having blue flowers, but the form commonly
found at Ames, Iowa, and LaCrosse, Wisconsin, is whitish
with occasionally a slight tinge of blue. Another species, D.
tricorne, which occurs in southern Iowa usually has blue flow-
ers, but on the limestone cliffs at Glencoe, Missouri, only
white flowers occur. I was therefore agreeably surprised to
find that in the great American bottom opposite St. Louis
near Falling Springs, in deep rich woods a beautiful pink
form occurred. Our painted cup {Castilleia coccinea) usually
has red flowers, but at Madison, Wisconsin, where I noticed
the plant for several years in a swamp, the yellow flowered
form occurred. Mr. Upham, however, states that some
years upon districts ten to twenty miles in extent the flowers
are all yellow, elsewhere scarlet with occasional yellow flow-
ers intermixed. Fritz Mueller has observed that some plants
do not flower continuously, but concentrate their efforts to
certain days. A species of Cyphella (one of the Iridaceae)
was observed in Itajahy, Brazil, to flower in profusion along
the roads for miles, but the following day it was not observed.36
In the bell-flower (Mertensia Virginica) the flowers at
different stages are variously colored. The buds are reddish,
when the flowers open they are violet; when
fertilization has taken place they change to blue. This
peculiarity of changing color after fertilization occurs in many
flowers like Missouri currant (Ribes aureu?n), cotton (Gossyp-
ium herbaceum), horse-chestnut (Aesculus Hippocastanum),
buckeye (Aesculus glabra), etc. This change in color, it is
thought, is developed to indicate to the insect that its ser-
vices are no longer required. Be this as it may^t is inter-
esting to know that color changes do occur. An insect
attracted by colors or odors should lose no time after it
reaches the flower to get the nectar. Many flowers are
therefore characterized by producing certain marks which
point toward the nectar, and as some one has said, “These
marks are to the insect what the finger-post is to the way-
farer, guiding and directing him to his desired destination.’’
These marks occur in the form of deeper colored portions of
the petals, sepals, etc., lines or hairs on the surface of the
corolla, stamens, etc. In the pansy these guides consist of
lines that are colored blue or purple. On the rose-colored
petals of some flowers there are a number of black rings,
lines, etdS/^Ve must now consider very briefly, nectar.
Nectar has bfeen defined by Prof. Trelease as & “fluid always,
usually sweet, often odorous, which is elaborated in any part
of a plant^ remaining where formed or making its way to
some other part; its raison d'etre being the necessity for the
removal of some useless or injurious substance, or for some
provision to attract nectar-loving animals to the plant for
some definite purpose.”Qlt is well known that special parts
of the flower or plant elaborate nectar; these are commonly
called nectar glands^ The minute anatomy of these has been37
studied by Trelease, Behrens and others. Trelease has
divided neotar pjlanHs into floral^ and extra-floral. Floral:
Jjeceptacjo, pish'!, atam^a, corolla, and calyx. Extra-floral:
Calyx, ordinary bracts, specialized bracts, involucre, ped
uncle, and leaf. The order Ranunculaceae is interesting as
regards the secretion of nectar. Some flowers are anern-
ophilous and without nectar, as meadow rue (Thalictrum dioic-
um), etc. (in buttercup (Ranunculus flammula) the honey is
secreted by little scales at the base of the petals.^) In Ranun-
culus auricomus the honey glands are at the base of the pet-
als. (In the pasque flower {Anemone patens var Nuttalliana)
honey is secreted by rudimentary stamens^ In a species of
clematis (Atragene alpina) honey is secreted by the basal half
of the filament. In marsh marigold [Caltha pafustris) honey
is secreted by the pistils. In the columbine (Aquilegia Can-
adensis) the honey is secreted by a fleshy thickening in the
extreme point of the spur of the petal^ In larkspur (Delph-
inium azureum) the honey is secreted by the two upper pet-
als which are inclosed by the spurred upper sepal. In Acon-
itum napellus the two posterior petals are developed into nec-
taries. (in Salvia and other labiates^the nectar is secreted by
a disc-shaped gland under the pistil^In borage (Borrago offi-
cinalis) it is secreted by the fleshy base of the pistil^ This
is retained by a short tube formed by the bases of the stam-
ens. In toad flax (Linaria vularis) the honey is secreted
by a prominent enlargement at the base of the ovary. After
the honey is secreted it passes down a smooth, narrow groove
which is lined by short, stiff hairs, and thence to the tip of
the spur.
COdors in flowers are due largely to the
Odors of Flowers.	»	.	, .	„
presence of nectar, but some flowers
have odors without nectar, f A bunch of hepaticas often pro-38
duces a decided odor, but there is no visible nectar^
The odors of flowers have been divided into five groups:
\Indolpjd, amiuoid, paiaffinoid, beuzonoid, terpenoid. The
inddtoid odors are frequent in aroids, stapelias, aristolochias
and some orchids. These carrion like odors are attractive to
insects the feed on carrion, like some flies and beetles. The
flowers have vivid spots and reddish brown veins. The ami-
noid group is closely related to the above, and is derived
from the amido derivatives in which one, two or three parts
of the water in the ammonia is replaced by the radical alco-
hol.
In hawthorn (Crataegus,) the odor is due to trimethyla-
mine It is similar in the flowers of pear (Pyrus communis )
Somewhat different is the odor in manna ash (Fraxinus
ornus,) horse chestnut (Aesculus liippocastanum), tree of
heaven (Ailanthus).
The benzoloid odors occur in various species of Dian-
thus, the odor of Asperula odorata, lily of the valley
(Convallaria majalis), Heliotropium, Reseda odorata,
etc. From this class one might distinguish special odors as
in heliotrope, violet, vanilla, etc. ("it is also noteworthy that
these same odors occur in plants distantly related.) Carna-
tion odors occur in some orchids as Platanthera, also in
Orobanche, Missouri current (Ribes aureum,) narcissus {R.
poeticus ) The paraffine odors occur in Valeriana offid-
nalis Ruta graveolens, grape (Vitis vinifera) honey
locust (Gleditschia triacanthos■) The odor from newly
filled honey combs is allied to some of the odors that belong
to this group, as buckwheat, white and other clovers.
The last group comprises the aetherial oils but more pro-
perly terpene, these occur at times in certain glandular hairs
or other parts of the plant, seldom in parts of the flower,39
but the odor of citcus flowers belongs here, also in certain
species of magnolia [M. Yulan,) artillery plant (Dictam-
nu sjraccinella) ■
( It is to be noted also that some flowers produce several
kinds of odors, and it is especially important from our point
of view to recognize that some plants, although closely re-
lated, have entirely different odors.} Daphne alpina, va-
nillin; D. Philippi, violgt; D. Balg ay ana, carnatign.
Kerner von Marilaun says anyone who is familiar with the
genus Rosa will recognize such species as alpina, pimpin-
ellifolia, arvensis, Indica, moschata, canina, gallica
and cinnamomea by their odors with closed eyes.CHAPTER V.
SPECIAL ADAPTATIONS.
Members of this family shows various
Rauuncuiaceae. a(japtations to pollination. Some of the
flowers are very conspicuous and are adapted to long-
tongued insicts, as species of columbine, (Aguilegia), Del-
phinium, and Aconitum• Buttercups, with shallow and un-
protected nectar, are adapted to a wide range of visitors,
Hymenoptera, Diptera, etc.
Clematis Virginiana, L. The flowers are borne in
large conspicuous clusters, dioecious. The nectar is easily
accessible and hence numerous small insects are attracted.
Robertson stated that three-fifths of the visitors are flies.
Some of the species of Clematis-, like C. Jackmanii, have
very conspicuous flowers. The European C. recta L- is
proterandrous and without nectar. In C. integrifolia, the
inner stamens secrete nectar. The Clematis Pitcherii,
Torr. & Gray, which flowers much earlier, is adapted to
bumble bees. In this species the filaments which secrete the
nectar are closely approximated so that bees are admitted by
a small opening. Robertson has made an interesting com-
parison of the insects visiting Isopyrum biternatum Torr.
& Gray, and Clematis Virginiana, L. The former,
which blooms in early spring, is visited by 31 Hymenoptera,
the latter by 9; bees and Syrphidae are less abundant on the
latter. It is visited also by 10 Tachinidae, 7 Muscidae and
11 other Diptera; the former by 4 of these.Jrl
Delphinium The flowers of the genus are conspicu-
ous. The European D. elatum L. as well as D. consolida
L■ are frequently cultivated; D. azureum michx. flowers in
July. The D. tricorne, michx. is native to Southern Iowa.
In the D. elatum, L. the five blue sepals are conspicuous,
very irregular, the upper one prolonged into a spur. Petals
four, irregular, two arch over the entrance to the spur, the
hairs form a path-finder to the nectar which is secreted by
the petals and contained in the spur. The pistil matures
first and bends down before dehiscence, but when mature it
points upward. I have seen B. pennsylvanicusia Wiscon-
sin. It is also visited by Synhalonia, and such Lepidoptera
as Danais and Papilio-
Aquilegia Canadensis, L The American Columbine
is frequent in deep rich woods and flowers in early May.
The conspicuous, scarlet flowers are yeliow inside and pendu-
lous. The five sepals are regular and colored like the petals.
Petals five, hollowed out into long, nearly straight spurs,
the opening is wide enough to admit the head of a bumble
bee. The nectar, which is secreted by the fleshy part at the
end of the spur, occurs in the upper part of the same The
flower is adapted to long tongued bumble bees; these reach
the honey by haging on to the flowers, grasping the base of
the spur with fore legs, and with their hind legs to the col-
umn forward by the stamens and pistils.
Several members of this order are culti-
vated for ornamental purposes. In the
common Barberry (Barberis vulgaris L.)
The yellow flowers are borne in racemes and contain
some nectar, which is secreted by two fleshy, orange colored
glands at the base of each petal. The honey collects be-42
tween the stamens and ovary. When the insect visits a
flower it thrusts its head into one of the angles and in doing
so comes in contact with the stamens which are sensitive,
they come forward and shed their pollen on the insect. It
now leaves the flower and as Hermann Mueller says, “Thrusts
its head or proboscis into the flower in
as many different ways as the different
positions of the flower require; now
under the stigma, now over it, now to
the right, now to the left. Its head
Fig, 20. Flower of common berberry (Berberis vulgaris). 1. flower seen
above; a, and sepals; b\ inner petals; c, nectaries; d, filaments; e, stigma; 2.
position of the stamen after springing upward; 3, petal with the two thick,
fleshy orange nectaries; 4-7, stamen in different stages of dehiscence. (After
Hermann Mueller.)
must soon be dusted all round with pollen and it must fer-
tilize every succeeding flower that it visits.”
P ^	.	Members of this order are among the
prettiest of our early flowers. Dicentra
spectabilis D C, Bleeding Heart, is commonly cultivated.
The purple colored flowers are heart-shaped pendulous, and
contain the honey in the two pouches at the base of the43
petals. Two of the petals are narrow, united at the top,
and enclose the six stamens, three on each side. When a
bee (JBombus) hanging from the flower puts its proboscis
into one of the two channels which occur on the petals, it
presses the hood and stamens to one side, but the style,
which is stiff, remains in position and is rubbed by the bee’s
body. A bee goes both to the right and left sides on each
visit. In this way it is certain to carry away some of the
polleD.
Corydalis cava■ The flowers are borne in racemes.
Each flower has two small, scale-like sepals that soon fall off.
The four petals occur in two pairs; one being spurred. The
nectar is secreted in the lower end. The other petal serves
as a support for insects when in the act of obtaining nectar.
The inner petals enclose the stamens and stigma. This has
been called the hood. It is indented on both sides and when
touched the six diadelphous stamens and pistil are liberated.
Behrens says:	“Previous to the opening of the flower the
pollen from the anthers is shed upon the stigma while it lies
in contact with them.” Self pollination would seem easy,
but if the flowers are enclosed by a gauze bag no seeds will
set. The insect on reaching the flower pushes its head be-
tween the hood and upper petal, the hood is pressed down-
wards and the pollen rubs against the lower surface of the
insect’s body. The hood returns to its normal position and
encloses the stamens and pistil.
The Cruciferae show great uniformity so far
Cruciferae.	r
as the structure of the flower is concerned
but variability in the number and position of the nectar
glands. The honey secreted by the glands remains on the
gland or is found in spaces between them. They are visitedu
by flies, especially Syrphidae, and small Hymenoptera. The
honey bee is abundant on some species of Brassica■ Some
species are also visited by Lepidoptera.
Brassica nigra Koch. Common mustard is a wayside
and garden weed. The yellow flowers are conspicuous, ar-
ranged in masses, and have a pleasant odor. It has four
nectar glands, two outside at the base of the petals and two
in front of the short stamens. The nectar occurs in large
drops on the glands where it is taken by the insect which in
doing so comes in contact with the pollen on both long and
short stamens, leaving some of the pollen on the capitate
stigma. In the absence of cross-pollination, self-pollination
occurs.
Our violets are all early flowering and the only
Violaceae.	.	.	&	J
species to be had during the summer is the
Pansy (Viola tricolor L). In the cultivated forms the
colors have been greatly changed. Three of the petals have
conspicuous pathfinders. The corolla is irregular, the lower
petal spurred at the base; stamens closely surround the
ovary, the two lower spurred. The spur acts as a nectar
gland while the lobed, hollow spur of the petal acts as a
receptacle. The insect thrusts its proboscis close under the
stigma into a hair-lined groove on the lower petal. The
anthers shed their pollen into this groove and thus the pro-
boscis becomes dusted with pollen. A small projection be-
low the stigma prevents the pollen on the insect from com-
ing in contact with the stigma. As the insect goes to an-
other flower it leaves some of the pollen on the stigma.
Of Viola pubescens. Ait. Robertson says:	“This is
yellow with dark nectar lines. The petaline spur is little
more than a gibbosity. The nectar-searching processes of the45
lower stamens are very short, being much wider than long.
The summit of the peduncle and the flower axis are strongly
curved so as to throw the Spur well backwards, giving the
flower a characteristic appearance, and this serves to limit
the insecls visits much more than the mere length of the
spur. ”
In regard to visitors Robertson says:	“Really, the pro-
per visitors are bees which are small enough to use the beard
as a support; so that the bumble-bees and butterflies may
properly be classed as intruders, even when they reverse.
For the proper visitors of the bearded violet we must look
to small bees, among which the Osmias are most important. ”
Many of the violets produce cleistogamous flowers.
The order shows considerable variations
Caryopliyllaceae.	.
as regards insect visitors. I he com-
mon door yard weed Stellaria media Smith is adapted to
short-tongued insects while Dianthus, Saponcia officinal-
is, Lychnis and others are visited by more highly special-
ized forms. In the more highly specialized form of flowers,
odors and colors are conspicuous.
Sapona/ia officinalis, L. The Bouncing Betty, is a
common weed in places and is adapted to nocturnal Lepi-
doptera■ Species of Sphinx are common here at Ames we
have observed. Hem oris thisbe, Sphinx Carolina, S.
Cher sis, Philampelus, Deilephila . ineata. The nectar
is secreted by a little ridge on the receptacle. Nectar is
contained at the base of the tube. The flowers are white
and have a strong odor in the evening. The calyx tube is
18 21 mm. long. The flower is strongly proterandrous.
The outer stamens protrude first, dehisce and spread apart.
Then the five inner stamens dehisce, the styles are still46
closed, wheD, however, the anthers have withered the two
styles lengthen and spread apart.
The Common Cranes bill, (Geranium macu-
latum, L.) is common in woods. The dark
lines of the petals converge to the base of the petals where
the nectar is found, which is secreted by five glands at the
bases of the outer stamens and protected from rain by hairs.
The flowers are proterandrous; the five stamens dis-
charge their pollen over the center of the flower and after
wards the five inner do the same. The anthers commonly
drop off before the stigmas expand. Robertson observes
that during rainy weather they may be in the male stage for
several days, but during warm weather they go through both
stages the same day. It is visited by the honey bee, bumble
bees, Diptera and some Lepidoptera■	Some of the
European species have lost all power of self-fertilization.
Oxalis■ Some species of the genus Oxalis are trim-
oiphic. Hildebrand found fifty-one species trimorphic.
Geranium- Our commonly cultivated Geranium
(.Pelargonium zonale, Willd) colors, various, in many
darker zones leading to base of upper petals, these overlap,
forming a groove leading down to the nectary, which is
made up of the base of one sepal, forming a long narrow
tube. Nectar is secreted by the hairs on lower side near the
base of this tube. The flowers are proterandrous. The
seven stamens mature first, five before the two shorter which
occur in front of the opening to the nectar tube. After de-
hiscence the pistil lengthens and the style spreads out. The
geraniums with us are frequently pollinated by humming
birds.47
Flowers very commonly polygamous or dio-
ecious, flowers greenish, inconspicuous, but
very fragrant ovary with an adnate fleshy disk of five nectar
glands which secrete the nectar. This hears the petals and
stamens, calyx short The stamens held by the petals which
separate only at base, which forms a kind of a head, when
mature the stamens are released, thus allowing the pollen
to be thrown on the insect.
FIG. 20. A, Flower before the removal of petals a. B, After removal of
petals, b, c stamens which have dehisced, d just in the act of dehiscence.
Many of the legumes are excellently adapted
for insects. In the Papilionaceae the flowers
are irregular and with some exceptions expose the stigma
and pollen to contact with the ventral surface of the insect.
The two lower petals are united to form the keel and enclose
the reproductive bodies. The wings serve as a resting place
for insects, to depress the keel, keep it in place and bring it
back to its place after depression. The manner in which
the keel returns to its place varies in different species.
Most of the Leguminosae are insect pollinated, though some,48
like Erythrina, are adapted to humming birds.
Phaseolus vulgaris L. The common bean is abund-
antly self-pollinated, it has interesting adaptations for secur-
ing cross-pollination. The flower of the bean consists of the
green calyx and the corolla, which is made up of five parts,
the upper |>art called the standard, two laleral wings, and a
keel made up of two petals. The keel is spirally coiled and
contains the stamens and pistil. The oblique stigma is on
FIG. 81.
Fig. 21 Common bean (Phaseolus vulgaris). 444. the flower. 446. showing spi-
rally coiled keel. 448, part of keel removed, showing style 447, the figure to
the right showing Style and pollen only. (After Gray)
the tip on the style, which is bearded, near the end on which
the pollen is discharged. An insect in searching for the
nectar at the base of the flower lights on the two lateral
petals, coming first in contact with the stigma, deposits pol-
len from another flower. The weight of the insect causes
the style to protrude. In scarlet runner (Phaseolus mul-
tiflorus) the arrangement is similar except that the keel
with its style is so bent that when pressed down, the style49
comes out, points downwards and towards the left, and
Francis Darwin has shown that the tenth stamen, which is
free, bears an appendage which prevents a bee from taking
the honey, except from the left side. On the college grounds
the early flowers are invariably sterile. But those produced
in August are fertile.
In the closely related Strophostyles angulosa Ell. the keel
is bent strongly to the right, and occurs in such a way that its
tip stands over its base. Robertson says:	“The base is
large and sac-like and is produced above into a ridge which
opposes the passage to the nectary. The left wing is turned
to the right so that the bee is required -to alight upon the
right side, and she enters the flower between the tip and the
basal process of the keel. Seizing this process with her
front feet, the bee pulls the keel downward and backward,
whereupon the stigma and the pollen-laden brush of the
style sweep out over her thorax. In this way the stigma re-
ceives pollen already deposited by another flower, and the
style-brush leaves a new load.”
This plant, along with several other Leguminosae, es-
pecially the Cowpea of the South, Vigna Sinensis, Hassk. has
conspicuous extra floral nectaries, on which Vespa maculata
and Formica are common. Robertson reports having found
several Hyme-noptera (Andrinidae, Yespidae, Formididae,)
Diptera and Hemiptera, on Strophostyles angulosa, Ell.
Apios tuberosa. Another near relative of Phaseolus is
Apios tuberosa, Moench. which has a large standard with a
rather firm texture, at the tip of the standard is a small boss,
as seen from the back, or a shallow sack as seen from the
front. The sickle shaped keel is arched and fixed into the
notch at the upper end of the standard and it remains in this
position unless touched by an insect. When an insect touch-50
es the flower in quest of nectar, which is secreted as in other
Leguminosae, it pushes forward into the space under the
arched keel, and by lifting from underneath dislodges its
apex; when first the stigma and then the anthers are brought
against some portion of the insect’s body and against the
same portion in succeeding blossoms, thus effecting cross-
pollination.
< Red Clover. Trifolium pratense. The corolla consists
of the following parts:	An upper larger petal known
as the standard, two lateral petals known as the
PIG. 22.
Pig. 22. Red clover (Trifolium pratense). 1. Flower from below; 2, from above
after the removal of the standard; 3, the kee/ forced apart; 4 and 5, wing pe-
tals. 6, stamens and pistil emerging from keel; a, calyx, b. tube formed by the
union of filaments; d, the concave inner part of the wings; h. keel; i. style;
m. anthers. (After Hermann Mueller.)
wings, and two lower petals resembling the keel of a boat,
which are united and are commonly known as the keel. The
,keel contains the ten stamens, each stamen consisting of an51
anther, to this is attached a thread-like affair known as the
filament. Bat in th s case of clover, however, the filaments
are united to form a tube; the anthers contain the pollen.
The pistil is also found in the keel. The lower portion is
the ovary, the narrow neck is known as the style, the tip is
the stigma The color of the clover flower is especially at-
tractive to insects. The honey which the insect seeks is con-
tained in the tube formed by the union of the fine thread-like
bodies, or filaments.
When an insect like the bumble bee lights on the flower,
it uses the keel and wings (the latter being attached to the
tube containing the nectar) as a resting place, its weight
pressing the keel down and causing the pistil and stamens,
the latter being somewhat shorter than the pistil, to come in
contact with the under side of the bee’s head. The insect is
certain to leave some of the pollen from another flower on
the stigma. The honey is obtained by the insect when it
thrusts its proboscis into the united filaments of the stamens,
the tube thus formed has a slit on the upper side to give
place for a free tenth stamen. Self pollination, or pollination
of the flower from its own stamens, is not excluded, as the
iusect leaves the flowers.
In order to reach the honey an insect must have a
tongue from .3543 to .3937 inches (9 to 10 millimeters) long.
The honey lies from .2755 to .3937 inches (7 to 9 millimeters)
deep. Any insect sufficiently heavy to press down the
keel can pollinate the flower. Bumble bees are, of course,
the common pollinators. Prof. Osborn informs me that he
has observed two common species (Bombus pennsylvanicus
and B. fervidus). We have found Bombus americanus B.
s, Apis mellijica. We also observed Alydus pluto, En-
chistus variolarans of Hemiptera. Of the Coleoptera the52
following were' observed:	Lachnosterna gibbosa, Tetratopus
femomtus. My friend, Mr. Robertson, records several more.
The honey bee can, no doubt, pollinate red clover, as they
~often collect pollen?] I have taken an interest in bees for
many years and have given some attention to red clover and
honey bees. The following paragraph, from a paper publish-
ed in 1888, may be of interest:	“In the summer of 18S3, in
the vicinity o£ La Crosse, Wisconsin, I noticed large num-
bers of honey bees on the flowers of red clover. In many
cases they were actively collecting pollen, but in some cases
honey through perforations in the corolla, made by some
other insects.” Hermann Mueller says the honey bee “usual-
ly visits the red clover only for its honey, which its probos-
cis is not able to reach in a legitimate manner—yet now and
then I have seen hundreds of huney bees on a patch of red
_clover, all busy collecting pollen.” Here at Ames I have
^seen red clover visited by several butterflies, especially the
largo, red butterfly (Lanais archippus), cabbage butterfly
(Pieris rapae), yellow butterfly (Coleusphilodice), also C. eury-
theme and a fly (Bombylius). Red clover is especially adapt-
ed to larger beey but Hermann Mueller of Germany, and
Robertson, of Uarlinville, Illinois, records a -large num-
ber of butterfly visitors. Thirteen out of twenty visitors be-
longing to the butterfly family were observed in Illinois.
_ There is no question but that they do occasionally pollinate
_red clover and effect cross fertilization Robertson writes.
“Bumble bees depress the keel so that their heads and probo-
'~~scide8 are well dusted with pollen, but butterflies can insert
their thin tongues without depressing the keel, and even if
they get a little pollen on their thin proboscides, it is apt to
be wiped off by the closely approximated tips of the petals,
which close the mouth of the flower53
Th. Pergande expresses the belief that different species
of thrips, which were found in many kinds of flowers, may
effect cross-pollination. Osborn informs me that two
kinds of thrips are common in clover blossoms. Thrips
tritici and Phloethrips nigra, but these certainly cannot gen-
erally effect cross-pollination.
Can the honey bee effect cross-fertilization in Mammoth
clover (Trifolium medium)? It probably can do so as it does
in common red clover. I have not studied the flowers of
mamoth clover carefully, but so far as I can see, the flowers
of the forms in the college collection are about the same size
as those of red clover. One form has much smaller heads
and the flowers are somewhat smaller, but I am inclined to
think that mammoth clover is pollinated principally by bumble
bees. The work of honey bees in pollinating white and alsike
clover is well known, in fact, they can easily accomplish this.
One other thought suggests itself to me in this connection.
I believe that it is generally supposed that the second crop
of clover produces more seed than the first. This, I think,
is due to insects, there being a much larger crop of bumble
bees at the time of the second bloom than during the first
bloom.
White Clover. The flowers of Trifolium rcpens, L.,
are massed together in the form of a head and
hence are quite conspicuous. The odor also helps to attract.
The standard has a groove which leads to the nectary. The
nectar is secreted at the bottom of the tube formed by the
union of the filaments and can only be reached by the open'
ings, one on each side of the free tenth stamen. An insect,
in order to reach the nectar, puts its proboscis underneath
the standard. It uses the wings and keel as a resting place,
pressing down the latter and causing the stamens and pistil54
to protrude. The stamens and pistil come in contact with
the lower surface of the body. When the insect leaves the
flower the parts return to their positions. At the base of the
expanded part of the wings is a pouched swelling
which causes the wings to cohere with the keel and serves the
purpose ot bringing these back to their positions. Honey
bees are the active pollinators. It is also pollinated by small
Lepidoptera. Short tongued insects are included. Self-fer-
tilization seldom if ever takes place. Darwin found that
when insects are excluded it is but slightly productive.
Sweet Peas. The flowers of sweet peas are conspicuous
as to odor and color. The margins of the wings
of the corolla adhere to the keel by a process which folds
inwardly, the standard also fits into these wings. It thus
requires considerable force to press down the keel which
contains the pistil and stamens. The style is flattened and
hairy along the inner side. These hairs contain the pollen
and as the keel is pressed down the pollen is swept out.
Amorpha fruticosa, L. The flowers are purplish and
arranged in a conspicious spike In this plant the keel and
wings are wanting and the standard surrounds the stamens
and pistil which are exserted. The flowers are proterogyn-
ous, here at Ames as elsewhere, as observed by Trelease,
Robertson, Mueller and Beal. It is visited by Bombus and
the honey bee here at Ames.
The Lead Plant, A. canescsns, Nutt., flowers nearly a
month later at Ames and is not a competitor with it as it
grows in different situations.
Partridge Pea. This leguminous plant is conspicu-
ous in dry situations and has some interesting
features, first described by J. E. Todd. These are described
by Robertson as follows:	“The sickle shaped pistil is turned55
either to the right or to the left, holding the stamens in such
a position that it touches the bee upon the side; the flower is
therefore an example of what Delpino calls a pleuYotribe
flower. Ten lonsr black anthers with terminal pores turn in
an opposite direction from the pistil. The petals are bright
yellow, the upper ones are provided with a little red at base
which seryes as a pathfinder, but not as a nectar guide, since
nectar is wanting. All are widely expanded and flexible ex-
cept the lateral one toward which the anthers turn, which is
erect and strongly incurved and so stiff that it commonly
breaks on being bent back.”
“The flowers are visited exclusively by bumble bees,
females and workers in search of pollen. Landing upon the
anthers they seize them between their mandibles and stroke
them downwards with a sort of a milking motion. The pol-
len being thus forced out of the terminal anther-pores, falls
either directly upon the bee or upon the lateral petal which
is pressed close against the bee’s side. In this way. the side
of the bee which is next to the incurved petal receives the
most pollen. Both right and left-hand flowers are found
upon the same plant. A bee visiting a left-hand flower re-
ceives pollen upon the right side and then flying to a right-
hand flower, strikes the same side against the stigma.”
The plants of this order are adapted to short-
Rosaceae. tonguecj iI)8ectS; then too, the large number of
stamens causes it to be sought by a numerous class of Dip-
tera and Hymenoptera. The nectar is secreted by the wall of
the tube of the receptacle. The amount of this secretion
varies, in some cases no nectar is secreted. Some of the
species are delightfully fragrant, others are without any
odor.
Native Plum. A conspicuous plant in woods, sometimes56
forming thickets. The whi’e flowers are conspicuous with a
decided odor. It flowers from the latter part of April to
early’May, depending on the season. The flowers are slight-
ly proterogynous, when open they are ready to receive the
pollen. Some varieties of the European P. domestica L. are
more strongly proterogynous. The stamens mature some-
what later. They are as long or a little longer than the style.
Self pollination may occur, though in some cases this is prer
vented by self impotency, in some varieties. Prunus hortu*
Ima, Bailey, as I have had occasion to observe for seven
years, has imperfect flowers.. Many flowers of our native
plum have since been examined and I have never failed, in
some individuals at least, to find this characrer well pro-
nounced.
In all cases examined the suppression was all in the di-
rection of the pistil. The stamens in all cases were well de-
veloped. In these imperfect flowers the pistil is short, scarce-
ly as long as the calyx tube. In the Rjllingstone the pistil
is entirely absent in many cases.
To see how generally the pistils were rudimentary, a
number of counts were made on branches selected at random
on several trees. On the first tree 79 per cent of the flowers
counted were perfect and 21 per cent imperfect; on the sec-
ond tree the flowers 76 per cent perfect and 24 per cent im-
perfect, while in the third tree but 31 per cent of the flowers
were perfect and 69 per cent were imperfect. Prof. Goff has
observed similar facts; he states:	“Imperfect pistils or an
absence of pistils, has also been offered as a reason
for infertility in native plums. Unquestionably this defect
sometimes occurs. Professor Bailey mentions a wild plum
tree of his acquaintance that bears flowers without pistils,
also that, in the season of 1892, only about one flower in57
twelve of the Newman plum at Cornell University had a
perfect pistil. I have made careful observations on this
point in our own Plum-trees during the present season and
find a marked difference in varieties. as to the percentage of
perfect pistils.”
The insects most common on the plum are honey bees
and other small Hymenoptera and Diptera■ During the
evening it is abundantly visited by cut worm moths.
Choke Cherry The w^'te dowers, borne in long racemes,
are conspicuous. Prunus Virginiana, L.,
is likewise proterogynous. Self-pollination as well as cross-
pollination occurs. Prunus serotina Elir., which flower sev-
eral weeks later, has the same general arrangements and
like the flowers of choke cherry, have a somewhat disagree-
able odor, which accounts for the large number of Diptera
.which visit it.
Washington Thorn, The white flowers are borne
in corymbs and are very conspicuous. They are
proterogynous. The nectar is secreted in the re-
ceptacular tube and is not concealed. It is visited by many
Diptera and small Hymenoptera, among them the honey bee,
also some Coleoptera and Lepidoptera. Of the four species,
Crataegus punctata Jacq. C, coccinea, L., C. mollis and
C. tomentosa, no two flower at the same time about Ames.
Wild Crab■ This blooms in and about Ames about
the middle of May. Pyrus coronaria, L. is one
of the most interesting of our native plants, The large,
showy and attractive purple-colored corollas are attractive to
insects because of the delightful fragrance. The filaments
of the numerous stamens form a circle about the summit of
the receptacle tube. These are alfco directed upwards and58
inwards, thus concealing the nectar effectually, and barring
out short tongued insects. Robertson says:	“The nectar
is leached by a bee
thrusting its ptoboscis
between the separating
ends of the filaments,”
The flowers are protero-
gynous; self-pollination
is prevented because the
stigmas are much longer
than the stamens.
Strawberry. The
flowers of the strawber-
ry are conspicuous be-
cause collected in patch-
es. Nectar is secreted Pig, 33. Klower Jl£r *berry.
by the receptacle at the
base of the filaments, next
to the outer row of pistils
where it is held. The
flowers are gynodioecious,
the fe^male flowers are
smaller and bear shorter
stamens. The staminate
in some cultivated varie-
ties, as the Bubach are
very large. The plant
may be self-pollinated, al-
though nearly always
Fig-. 24. FiowerFofGst?twberry.	cross-pollinated. It is vis-
ited by honey bees frequently at Ames and also by species
of Halictus-59
The red raspberry, Rubus strwosus, Michx.. has
Rubus. . .	,	, ■	,	i
white petals and is not nearly so attractive as the
blackberry (R. villosus, Ait.) Nectar is abundantly secret-
ed by the flattened disk between the pistil and tilaments
which is obtained by bees inserting their proboscides between
the stamens and pistil. The stamens are inflected inwardly
toward the pistil. The stigma is receptive before the
stamens mature. In the absence of insect pollination, self-
pollination can take place. Visited by Hymenoptera, honey
bees frequent. Rubus villosus is much more attractive.
The petals are large and white. Nectar is secreted as in Red
Raspberry but is more difficult for insects to obtain. It is
visited by honey bees and Robertson records several species
of Bombus for Carlinville, Illinois.
Members of the order are adapted to a
SAXIFRAGACEAE. ...	, .	.	. ..	K..	,
wide class of insect visitors. Many of
the species occur in colder portions of the world. The Sax-
ifragas are common in alpine and subalpine regions, some
occuring in the bogs and meadows of the Eastern and North-
ern States. Species of the genus Ribes, though originally
of the colder regions, have a wider distribution. The
species of the order vary as to their insect visitors. Most
common are the Diptera and Hymenoptera. Herman Muel-
ler has called attention to the fact that the flowers of many
species of the genus Saxifraga are proterandrous; the
anthers ripen one after another. He also notes that in
Chrysosplenium alternifolum, L., small snails creeping
about over the stigmas and anthers, carry the pollen grains
upon the stigma with their slimy bodies. Parnassia
palustris, L., which is native to Northeastern Iowa, has
some peculiar nectar glands. “Each consists of a short,
broad peduncle, broadening above into a fleshy disk which60
secretes honey in two shallow depressions on its inner side,
leaving it fully exposed. Above it gives off seven to eigh-
teen yellow, knobbed, glandular bodies, probably for the
purpose of making the nectaries more conspicuous. These
yellow, knobbed affairs look very much like little drops of
fluid. Mueller states that these drops are quite deceptive,
so much so that flies- are deceived by their appearance.
Phi adelphus. The flowers are crowded in large,
cream-white clusters and are proterogynous. The numerous
anthers stand in and around the stigmas before and after de-
hiscence and are as long as or longer than the pistils. The nec-
tar is secreted in the fleshy disk in the upper part of the
ovary. In the absence of cross-pollination, self-pollination
can easily take place. In is adapted to a large class of visi-
tors. An east European species with small flowers is proter-
andous. The flowers are sweeter scented, being that of pine
apple.
Ribes The various species of the genus Ribes differ
in regard to the depth at which the nectar can be obtained.
The Ribes alpium is visited here at Ames by various species,
Diptera the common honey bee, and Bombus Pennsyl-
vanicus. The Ribas gracile Michx. and R Cynosbati L.
are both early flowering species and are visited by Apis mel-
lifica, Bombus Pennsylvanicus ■ The western Ribes aur-
eum Pursh. ;s frequently cultivated, and has a long calyx
tube and small erect petals. The calyx is colored yellow,
petals also yellow, flowers very fragrant. The petals, after
fertilization change from yellow to bright red. It is adapt-
ed to long-tongued bumble bees.
Loosestrife, Lythrum Salicaria L. is a
Lythraceae.	.	. _	,	.	,	,	,	,
native of Europe but sparingly naturalized61
in Eastern North America and frequently cultivated.
Flowers purplish, petals six to seven. Spiked Loosestrife
is classic because of Darwin’s work in connection with
heterotristylous flowers. Darwin proved beyond a question
that the reproductive bodies, when of different lengths, behave
like different species of plants, that is to say, the pollen taken
from a short stamen and placed upon the long style in the
same flower or plant has no effect. So, too, of all the other
stamens taken from the same plant. Darwin also demon-
strated that the pollen grains differ
as well as the stigmatic papillae.1
The pollen grains of the longer
stainent are green, those from the
PIG. 25.
Fig-. 25. Lythrum salicaria. 1, long styled flower from above, with two sets of
stamens; part of calyx and corolla removed; 2, mid-sty led flower; 3. short-styled
flower; a, long anthers and stigmas; b. mid-styled; e, short; d, honey gland;
/, mid-styled flower viewed obliquely. (After Hermann Mueller).
middle size and the shortest are yellow. The pollen grains
also vary in size. The longest stamens have the largest pol-
len grains and the shortest, the smallest.
In this plant three kinds of flowers are produced. One
plant produces only a short style with long stamens and
mid-styled stamens; a second plant has a long style with62
short and mid-sty led stamens; a third has a medium style
with short and long stamens. In order to have full and
complete fertility pollen must be brought from the long sta-
mens over to the long-styled, short stamens over to the
short-styled, and mid-stamens over to the mid styled form.
The honey in this plant is accessible to a large class of
visitors.
Evening Primrose is a common weed. It is
adapted to nocturnal Lepidoptera\ but also to
long-tongued bees. The flowers are bright yellow, open
partially during the day but produces the greatest amount
of odor during the evening. Trelease has observed that the
Oenothera sinuata, L. is visited by the humming bird.
Some species of Oenothera produce cleistogamus flowers.
Fire Weed■ Epilobium angustifolium, L. is wide-
ly distributed in the northern hemisphere. The flowers are
strongly proterandrous. The large and showy flowers are
arranged in a spike, the widely spreading petals on short
claws. The style is bent downwards. Herman Mueller
says of it:	“The expanded lower ends of the filaments
form a hollow cone which encloses the base of the style and
the surrounding honey; where the style issues at the apex of
this cone, hairs upon the style prevent the entrance of rain-
drops, while insects easily gain access between the fila-
ments.”
In young flowers the stamens, covered above with pol-
len, project forward as an alighting place for insects, while
the style is still shorter and bent forwards with its stigmas
folded together; in older flowers, the empty stamens are
forwards, and the style, greatly increased in length, pro-
jects forwards with its four stigmas outspread and recurved.63
Alighting, sucking, and pollen-collecting are thus all made
easy, cross-fertilization in case of insects-visits is insured,
Fig:. 26. A flower of evening prim-
rose (Oenothera biennis) cut lengthwise
shows a very long tube. (After Ker-
ner von Marilaun.)
FIG. 26 A.
Fig. 26 A. 3, Pollen of
Oenothera biennis.
and self-fertilization rendered impossible. In fine weather,
sufficient insect-visits are always insured by the conspicuous64
color, size, and grouping of the flowers, and the abundance
and accessible position of the pollen and honey.”
In the Rocky Mountains this species is commonly visited
by several species of Bonbun■	i -
PIG. 27.
Fig. 27. Dichogamous flowers. 1 FpUobium angustifolium showing devel-
opment of stamens first (proterandrous) with a bumble bee on one of the flow-
ers. See upper flowers. (After Kerner von Marilaun.)
The Cucurbits are usually said^ to be mon-
oecious or dioecious, although G. O.
Mueller says occasionally polygamous. It has been known
for some time that the same species are proterogynous and
Cucurbitaceae.65
dioecious Crozier says in regard to the watermelon:	“In
making some crosses today on the Volga watermelon, a var-
iety from Southern Russia, I discovered that the so-called
pistillate flower possessed stamens.”
Gucurbita pepo, Linn. The different forms of this spec-
ies have the same general arrangement and structure as are
found in C. maxima■ The odor of the large yellow flowers
is not so pleasant as in that species, but is rather disagree-
able. Nectar is abundandt and the insects reaches it in
about the same way. The flowers open early in the morn-
ing and when mature the pollen falls out, frequently filling
the bottom of the flower. The grains are very large, round
and spiny. When placed in water the spines in several places
are thrown ofl, and in a short time the contents pass into the
water.
Insect visitors:—Hymenoptera, Apis mellijica, Bom-
bus pennsylvanica, Formica rufa. Coleoptera, Diabro-
tica longicornis and D. vittata, Fab.
Citrullus vulgaris, Schrader. The pale yellow corol-
las of the watermelon are widely spreading. The honey is
secreted at the base of the flower. It is easy to observe how
the honey bee obtains its nectar. It uses the petals as a rest-
ing place and obtains the nectar through the opening. It
first probes one side and then passes over the stamens to the
opposite side of the flower from which the nectar is taken.
When its work is finished it flies to another flower. Its visits
are confined cheifly to one variety but occasionly other var-
ieties are visited. It is noticeable that when flies collect pol-
len, honey bees flit about the flower a moment, then go to
another. The flowers are open all day.
In the insect visitors the Hymenoptera were represented66
by Apis mellifica and tbe Diptera by several species of
Syrphus flies.
Lagenaria vulgaris Ser. The musk scented flowers of
the dipper gourd have a funnel or bell-shaped calyx with a
long tube. The white petals are persistent a much longer
time than in Cucurbita pepo and the nectar is not so easily
accessible and exposed as in (Jitrullus and Cucurbita.
The three stamens effectually block the way for the larger
insects. The flower is adapted to humming birds, which can
easily get to the nectar with their long tongues. The color
and odor would seem to indicate that it is adapted to Sphingi-
dae, but as the plants were so far away observations were not
made at night. In addition to the humming bird,. Bombus
pennsylvanicus was observed collecting pollen. Diabro-
tica vittata was also observed covered with pollen.
UmbelHferae Members of the carrot family are not highly
specialized; nectar occurs in open flowers
and is accessible to short tongued insects. The individual
flower is not conspicuous, and so far as our own species are
concerned, are without the attractive flowers, but since the
flowers are massed they are rendered attractive. Zizia and
Pimpinella are proterogynous while Heracleurn and tSlum
are proterandrous. Mr. Robertson speaking of insect visit-
ors says:	“The character of the visitors of UmbelHferae»
therefore, must depend upon the insects to which they are
exposed, i. e. upon the time of blooming. Indeed, the time
of blooming is almost or quite as important as modifications
to hide the nectar. If we take three white-flowered forms
with exposed nectar, but appearing at different times, we
will find the extremes in characters of visitors. Thus, Eri-
genia shows the highest proportion of bees EulophuS the
highest proportion of flies, Cicuta the highest proportion of67
lower Hymenoptera. Zizia, Polytaenia and Eryngium agree in
showing a "preponderance of Hymenopera over flies as an
effect of concealment of honey. Pastinaca, Cicuta and
Sium show the same result as an effect of time of blooming.
Forms with hidden nectar also show marked contrasts on ac-
count of time of blooming. Thus, in the case of Zizia
which blooms in May, one-half of the Hymenoptera are bees,
while in Eryngium, which has more deeply-seated honey
but blossom in July, only one-third of the Hymenoptera are
bees.”
Cow Parsnip. This large, coarse perenuial grows in
deep, rich woods and bears large and broad) white .umbels.
The larger plants have two or three secondary umbels and
one of the third order. Robertson gives the proportion of
male and hermaphrodite flowers in different umbels as fol-
lows:	‘'First order, o male and 420 hermaphrodite in nine-
teen umbellets; Second order, one hundred and twenty
male and three hundred and three hermaphrodite flowers in
twenty umbellets; Third order, three hundred and eighty-
nine male and forty-six hermaphrodite flowers in twenty um-
bellets.” From this table it will be seen that those of the
first order are entirely hermaphrodite while those of the third
order are almost entirely male. The same relation is borne
out here at Ames. The hermaphrodite flowers are proteran-
drous. It is abundantly visited by Diptera, especially Syr-
phidae and by some Hymenoptera as the honey bee. In the
Rocky Mountains, where I observed the plant, small Hy-
menoptera and Syrphidae were common.
The order shows considerable variation as
Caprifoliaceae. regar(]g pollination. On the one hand it
is well adapted to Lepidoptera, Sphingidae, birds, and long-
tongued Hymenoptera, and on the other, in case of Adoxa68
and Sambucus, to short-tongued insects. The Weigelia rosea,
like Eibes aureum, changes its color after pollination.
Honeysuckles. The flowers of Lonicera sempervirem, Ait.
are nearly regular, trumpet-shaped, the deep red corolla is
conspicuous but has little odor. It projects obliquely up-
wards and the corolla tube is lined with hairs. Stamens five,
as long as the style; pistil and stamens maturing at the same
time. The nectar is secreted in the lower part of the tube
and is very abundant. In this locality the humming bird,
Trochilus colubris, is a common visitor as are some of the
larger Lepidoptera as Papilio turnus. The humming bird, in
a single visit, takes the nectar from a large number of
flowers.
In Lonicera Sullivantii, Gray, the flowers are irregular,
white with a purple tube, and are borne in clusters. The five
stamens are situated above the declined style Nectar is
so abundant that it rises in the tube and is protected by a
copious development of hairs. It is regularly pol-
linated by humming bird Lonicera Tartarica, L. the
honey is secreted and lodged in the shallow pouch at the base
of the tube. It flowers three weeks earlier and has a pleas-
ant odor and is conspicuous because of the color. Apis
inellifica and Bombuspenmylvanicus are frequent visitors.
„	.. The order is the most extensive of all flower-
Compositae.
ing plants—nearly one tenth of all plants be-
long to this great family. As an illustration, let us take the
sunflower {Helianthus annuus) and ox-eye daisy (Chrys-
anthemum leucantJiemum). The so called “flower” is an
inflorescence known as a head. In the ox-eye daisy, the
flower of the outer row of florets, are transformed into a con-
spicuous white strap-shaped corolla known as the ray-flowers.
In the sunflower these are yellow but in both cases they serve69
to attract insects. Id some flowers as in dandelion, all of
tlie corollas are strap-shaped. In boneset, the ray-fl »wers are
absent.
This large order has some extreme varations, as in Am-
brosia which is anemophilous. In many the nectar is easily
reached by short tongued insects, as in Solidago Achillea.
In some thistles, as Cnicus lanceolatus, the nectar can only be
reached by long tongued insects. Where the individual flow
er sometimes lacks in attraction the ray flowers increase in
conspicuousness.
Vernoniafasciculata Michx. grows in marshes. The tall stems
bear numerous heads of purple flowers. The long tubular
flowers are adapted to long tongued bees and flies, also Lepi-
doptera. The flowers are proteraudrous, the pollen being
carried out by the brush hairs on the style.
The Eupatorium ageratoides L. is also without ray flowers
but grows in woods. It flowers at the same time chat Ver-
nonia does. The E. purpureum L. var. Maculatum grows
in woods and is a competitor with the above. The purple
color of the flower renders it more attractive. The E, pur-
pureum competes with E. perfoliatum, L. growing in similar
places, but is purple flowered.
In yarrow or milfoil (Achilla millefolium) the white heads
are attractive to insects. A single flower is small and incon-
spicuous, but many of these small flowers are crowded to-
gether in one head, and in addition the white ray-flowers
certainly render them conspicuous. The nectar is easily
reached by many insects. It is secreted by a small disc at
the base of the style. The flowers are strongly proterand-
rous. Each flower has five stamens. The anthers are united,
and when the flower opens the two divisions of the style are
closely appressed in a cylinder made by the five anthers.70
The anthers when mature, shed their pollen into the hollow
cylinder. The tips of the lobes of the style are furnished
FIG. 27.
Fig. 27, Yarrow (Achillea millefolium); 1, head from above; a, stigmas; b,
stigmas of disk flowers; c, anther cylinders in their first stage; d, about to
open; 2, flower of disk just opening; e, ovary; /, nectary; fl, style: ft, tube of
the corolla; i, filaments; ft, two divisions of the style; m, anther cylinder; 3,
disk flower pollen issuing; 4, older disk flowers; 5, tip of style of a disk flower,
first male stage: r, stlgmatic papillae; s, sweeping hair; p. pollen grains; 6-8,
Chrysanthemum lencavthemum; 6, disk flower (male stage); .8, tip of one stig-
matic branch seen from inner side. (After Hermann Mueller).
with hair and as the style elongates it brushes the pollen out71
with remains attached to the hairs. When older, these
branches turn back and an insect going to a flower cannot
but help get some pollen on its body, and as it goes to an-
nother flower it is almost certain to leave some pollen on the
stigma. While cross-pollination is almost certain to occur,
self-pollination and self-fertilization may also occur.
Golden-rod. (Sol dago speciosa, Nutt) The flowers are
yellow, otherwise characters much the same,
as in yarrow. It is visited by the following insects:
Hvmenoptera — Apidae:	Bombus Virginians, sucking
honey Apis mellifica sucking honey (quite abundant.) Halic-
tns coriaceus, Augochloro pura, Cilissa Americana, Caliopsis
andreniformis. Sphegidae:	Crabro sp. Ammophila condi
tor. Ichneumonidae:	Trpphon sp. Lana Montana (?)
optera Meloidae:	Epicauta pennsylvanica feeding'on pollen.
Hemiptera—Phymata	wolfii.	Diptera—Muscidae: Stom-
oxys. Mesograpta marginata.
Sunflower. The flowers are collected in heads and are
made attractive because of the large yellow rays flowers. Like
yarrow they are proterandrous. At Ames they are visited by
Lepidoptera—Chryspophanus	thoe. Diptera— Bombylidae:
Bombylius■ Hymenoptera—Apidae: JVomada luteolai
gathering honey. Halictus Leronxii Mellissodes per-
plexa, gathering pollen and sucking honey. Vespidae:
Odyneris foraminatus.
Bull Ihistle. Bull thistle is common in pastures and
is rendered conspicuous because the purple flowers are col-
lected in heads. It is strongly proterandrous. In the first
stage a large quantity of pollen is pushed out by the style
from the opening of the syngenesious anthers. When the
style occurs outside of the anther tube a bunch of hairs may
be seen as brush hairs. These not only help to take out72
pollen but prevents it from falling to the bottom of the tube.
The pollen grains are spiny which causes them to adhere not
only to the insect but to the hairs on the style as well. The
slightly swollen anthers show spontaneous movements and
because of the shortening a mass of pollen is thrown out.
This happens when an insect seeks the nectar which is secret-
ed by a ring surrounding the base of the tublar corolla, as it
is in all other Compositae. In the later stage the pistil has
protruded showing the stigma. If the pollen has not been
carried away by the insect self-pollination may occur.
Bull thistle, flowers with us from the latter part of July
to September and is visited by many worker bumble bees.
Mr. Weed says:	“But they are not the large and handsome
bees found on the Arbutus in May, they are much smaller in
size and less attractive in appearance. The large specimens
which appear ' in spring are the hibernating females or
queens. In addition to bees many Diptera occ lr, especially
syrphus flies, Lepidoptera■ The Coliasphilodice as well
as Pieris, Danais archippits and Papilio turnus visit the
thistle flowers.
Our native Cnicus lanceolatus, var. discolor is equally
interesting.
Dandelion. In Taraxacum officinale the numerous
flowers are collected in a head. All of the flowers of the
head are alike and bright yellow. The head is open in
bright sunlight of the early morning and partially closed
about noon. When fertilized the “flower stem” contracts,
ripens its “seed”, and elongates when ripe, so that the
“seed” may be distributed. An abundance of nectar is pro-
duced which rises up for a considerable distance in the tube,
making it accessible to many insect visitors with short tongues.
The honey bee is a very common visitor as are also speciesof Bombus. Many Diptera, Syrphus flies, visit it Mueller
records 67 Apidae, 7 Lepidopttra, 25 Diptera and 16 other
insects. In the Alps Lepidoptera preponderated over the
Apidae.
Lobellaceae.
Cardinal Flower. Lobelia cardinalis L. is
common in the eastern part of the state, and
Fig. 28. Proterandrous flowers. 1, Aster alpinun part of a head, ray flower
partly cut off, disk flowers shown in center with protruding styles; 2, two lobed
style of aster showing stignutic lobes with brush hairs on tip; 4, 6. 6 and 7.
flowers of Centauren mnntana\ 7, the lobes of style curved back touching stig-
matic lobes; 8 and 9, Campanula persicifolia; 8, earlier stage; 9, lobes of style
curved back touching hairs on style; 10 and 11. Phyteuma nrbiculare. Stamens
surrounding the style of the younger flower. (After Kerner von Marilaun).74
not infrequent in low grounds in central Iowa. The irregu-
lar flowers are deep red; the tube is straight and split down
on the upper side. The lower lip is spreading, three cleft.
Trelease observed that the humming bird, TrochiluS Golub-
ris, visits this species and Robertson says he has never failed
to find them about the flowers. He says:	“The pendant
lip shows that the flower is intended to be visited by a bird
or insect which is in the habit of sucking the sweets from
flowers without resting upon them. I have also seen the
flower visited by Papilio philenor L. and P. trocilus L. ”
In Campanula rotundifolia the nectar
Campatmlaceae. .	» »	,,	,	...
is secreted by a yellow disk which sur
rounds the base of the style. It is covered by the bases of
five stamens. The interspaces are occupied by hairs, thus
protecting the honey from unbidden guests. In the
bud the three stigmas come together and form a cylinder,
the outer surface of which is covered with hairs. Before the
flower has opened the anthers are placed around the style.
The stamens dehisce and pollen falls on the hairs of the
style. When the stamens have dehisced they
shrivel up, the style lengthens out and the flower opens, it is
then thickly covered with pollen. When an insect visits
the flower takes off some of the pollen, the hairs on the
brush shrivel and now the three divisions of the style ex-
pand and curve backward. An insect coming from a
younger flower will leave pollen on the stigma. The flowers
are therefore proterandrous.
In the related Specularia perfoliata the early flowers are
cleistogamous.
Lricaceae• Laurel (Kalmia latifolia) a near relative75
of Rhododendron, discharges its pollen through a small
orifice at the apex of each cell. “In the flower bud each of
the ten anthers is lodged in a small cavity or pocket of the
corolla.” When the corolla expands the filaments are curved
outward and backward, and when the flowers are shaken by
bumbae-bees, which search the flowers for nectar in the bot-
tom of the flower, one after another of its stamens are liber-
ated. The pollen is thrown on the underside of the insect’s
body.
Some of the other members of the order have interesting
contrivances for the dispersal of pollen. In Vaccinium the
anthers are suspended inside the corolla with pores down-
ward, a shake causes the pollen to issue down on the insect's
body. In Winter Green (Pyrola secunda) the filaments are
curved like a letter S and are in a state of tension, the anth-
ers are in an erect position. When an insect touches the
petals the anthers are turned and in the meantime the pol-
len is turned out.
„ .	.	Persoon, in 1794. observed that the Cowslip
{Primula veris var. offiicinalis) existed
under two forms. Some most interesting experiments have
been made since that time. Darwin called attention to the
adapation for cross-pollination. He demonstrated that the
pollen of the short stamen, put on the long style of the same
flower, is inoperative. The same is true of the pollen from
long stamens when placed on the long style of the same.
These experiments were later repeated by Hildebrand and
John Scott.
In Primula elatior two kinds of flowers occur on dif-
ferent plants. One plant bears a long style with short sta-
mens, in which self-pollination is impossible; a second
plant bears a short style and long stamens. In this the76
pollen can easily fall on the stigma, but Darwin and others
have shown that the pollen is quite inactive on its own stig-
ma. There is another important difference. The pollen
grain of the long-styled flowers is smaller, while the stigma
Fig. 29. Cowslip (Primula). Left hand figure, long-styled flower; right hand
figure, short-styled flower; a, stamens; co, corolla; sf, style. Pollen^grains be-
tween. The smaller belonging to long-styled flower; the larger to short-styled
flower; magnified about 250 times. (After Lubbuck.)
is larger. The pollen grains of the short-styled flowers are
larger, while the stigmas are smaller. Insects carry the pol-
len from the short-styled flowers and leave it on the long-
styled, while the pollen from the long is carried over to the
short.
Darwin notes that in Primula veris the corollas of the
two forms are different. He sums up the difference as fol-
lows:	“The long-styled plants have a much longer pistil,
with a gobular and much rougher stigma, standing high
above the anthers. The stamens are short; the grains of
pollen smaller and oblong in shape. The upper half of the
tube of the corolla is more expanded. The number of seeds
produced is smaller and the ovules larger.
The short-styled plants have a shorter pistil, half the
length of the tube of the corolla, with a smooth depressed
stigma standing beneath the anthers. The stamens are long;77
the grains of pollen are spherical and larger. The tube of
the corolla is of uniform size except close to the upper end.
The number of seeds produced is larger.” He also notes
that the short-styled form is more fertile.
Mueller records many visitors such as Apis mellifira,
Bombus hortorum, while B. terrestris perforates; Diptera
(Bombylius).
Stfironema lanceolatum Gray, is common in low grounds.
It is from ten inches to two feet high and has yellow flowers
with purple centers. Robertson gives the following account
of its pollination:	“The flowers look outward and a little
downward. In the bud each corolla lobe enfolds an anther.
When the flower expands, the lobes carry the enclosed an-
thers with them, holding them while the stigma is receptive
and is exposed to insects—a fact to which my attention was
first called by Professor Pammel. After the anthers are re-
leased, the styles are commonly found bent outwards out of
the way of the fallen polling. Sprengel supposed that the
flowers of Lysimachia guadrifolia were nectar-bearing,
but failed to find nectar. He, and Mueller also, failed to
find honey in flowers of _£. vulgaris■ According to Kirsch-
ner, nectar is wanting in L. nemorum as well as in L. num-
mularia. I have been uncertain in regard to the occurrence
of honey in Steironema, but the visits of male bees seem
to indicate its presence, although these insects might search
for it in vain. They commonly fly about the flowers to find
the females, not trying to find honey.”
Lilac. The common lilac (Syringa vulgaris)
as well as the Persian (S. Persica) are com-
mon objects of cultivation. The flowers are borne in large,
loose panicles, conspicuous because of the lilac color and the
strong odor. The two stamens block the tube of the corol-78
la, effectively sheltering the nectar, which is secreted by the
ovary and occupies the lower part of the tube. The length
of the tube prevents short-tongued insects from getting the
nectar. Mueller thinks the honey bee can obtain only a
pait of the nectar. The stamens and pistil mature at the
same time. An insect in sucking the nectar first comes in
contact with the pollen, then with the stigma which is in-
serted lower down. Pollen does not adhere to a dry surface
but, must be moistened with nectar. Self-pollination takes
place in the absence of cross-pollination.
The Milkweeds are as interesting in their
Asclepladaceae. ....	,	, . ,
adaptations as are the orchids.
Common Milkweed. Hildebrand and Mueller long ago
called attention to the adaptations in this flower (Asclepias
cornuti.) The deeply five parted corolla is of purple color.
Next to the corolla is a crown of
five hooded bodies seated on the
stamens. The five stamens are
attached to the corolla, the fila-
ments are united in a tube which
encloses the pistil, and the anthers
adhere to the stigma. Unlike the
pollen of orchids, milkweed al-
ways has a pair of pollinia. They
are pear shaped and of yellow
waxy appearance. They hang by
a curved stalk from a dark colored
disc. These pollen masses are
taken out by insects as they suck
the nectar from the glands. The pollinia are attached to the
insect’s hairs, legs and tongue. Charles Robertson, in an ex-
cellent account of plants belonging to this family, finds that
a
PIG. 30.
Fig 30. Milkweed. Pollinia
of Asclepias cnrnuti: 2, flower
more magnified with some
parts removed-PIG. 31.
Fig-. 31. Milkweed. Pollinia of Asclepias cornuti; 1. flower as seen from the
side; 3, cross section of flowers; 4, pollinia; 5, foot of insect with pollinia.
(After Kerner von Marilaun.)
PIG. 32.
Fig. 32. Bumble bee (Bombits scuteUaris Cress) with pollinia from milkweed
(Acer cites long if olia)r (After Charles Robertson.)80
in Asclepias verticillata the pollinia are usually attached
to hairs of insects. In A'Clepias GOrnuti the pollinia are
more frequently attached to the claws, It is dangerous for
small insects to extract the pollinia and insert them into the
stigrnatic chamber. In one day Mr. Robertson picked
thirty-four dead hive bees from flowers. The feet become
entangled with the pollen masses. In another species, A.
sullivantii, he states that in a small patch bearing fifty-two
follicles one hundred and forty-seven dead bees were found.
In a single umbel he has often found four, and in one case
seven dead hive-bees. The insects pollinating these flowers
belong to the bees (Hymenopteru), butterflies and moths
(Lepidoptera), flies (Diptera), a few Coleoptera and
Hemiptera. Some of these visitors are useless since they
do not light on the flower. Others cannot extract the
pollinia. Humming birds have been observed, but Mr.
Robertson thinks ihey are useless.
The Gentians are among the prettiest of
Gentianaceae. ()ur autumn flowers. Most of the species
in Central Iowa have blue flowers, Q. Quinquefolia L.,
and Q. Andrewsii, Griseb. but G. flavida, Gray has white
flowers.
The G. Andrewsii Griseb., which we may take as a
type, grows in clumps in marshes and has a blue corolla
which is closed at the mouth, with toothed appendages,
fl he flowers are proterandrous. The stamens are united
with the corolla tube and the free ends occur over the pistil.
Bumble bees in search of nectar must possess a tongue 15-16
mm. long, which must be thrust between the filaments, In
speaking of the protection, Mr. Robertson says:
“There is no doubt that flowers were originally of such a
form that almost any insect could enter them and reach the
nectar. Many have narrowed the entrance by the develop-81
ment of tufts of hair, or of processes like the palates of person-
ale flowers, until all insects were excluded except bees.
These have kept on visiting the flowers until now they enter
completely closed flowers like those of Linaria." Weed
observes that owing to a change in color, the bee is able to
select the younger nectar-bearing flowers. In our Gentiana
quinquefolia Lam. the corolla is funnel form and open with
a row of conspicuous glands between the bases of the fila
ments.
Sweet William. The common cultivated
Polemoiiiaceae.	.
1 titox macuiata L. bears numerous pur-
ple flowers in an ample panicle. It has a pleasant odor and
is frequently pollinated by species of Sphinx. The related
P. paniculata is proterandrous, according to Mueller.
Many of the Borraginaceae are adapted
Borraginaceae.	. .
to short-tongued visitors, as in AlyosotiS',
others are adapted to long-tongued insects, as in Mertensia,
Lilhosperrnum, etc. These are adapted to long-tongued
bees and are also visited by Lepidoptera. The colors of the
flowers vary from the yellow of the puccoons and blue of
Mertensia to the white and blue of Myosotis-
In Lithospermum canescens the flowers are diptopo-
gamous or very variable. The L■ angustifolium produces
long, tubular, conspicuous flowers in early spring but as the
season advances they become gradually . shorter and are
finally cleistogamous.
Symphytum officinale L. Common Comfrey produc-
es a tubular, five-toothed corolla, inflated above. The
throat is closed by five small scales which probably serve to
compel the insect to thrust its proboscis between the proxi-
mutely closed anthers anrl to bar out useless visitors. The
stigmas and stamens mature at the same time.82
Common Borage. The blue flowers of Borrago offi-
cialis are commonly visited by honey bees which seek the
nectar that is abundantly secreted by the pale yellow fleshy
part at the base of the ovary. The anthers meet to form a
cone.
Mertensia Virgin tea DO. Blue Bells are conspicuous
in deep, rich woods. The blue, trumpet-shaped corolla has
a spieading limb; the slender filament are exserted. An
abundance of nectar is secreted by four glands at the base of
the ovary which alternate with the base of the carpels. Mr.
Robertson says:	“The blue color and the size of the tube,
together with the pendulous position of the flowers, indicate
an adaptation to the larger bees, but butterflies sometimes
hang on the flowers and draw out their honey. In the fol-
lowing list all the insects are intruders except Bombus,
Anthophora, and Synhalonia
Plants of this order are not abundant in
Couvolvulaceae. T	..	.	,	,	.	.
Iowa. Most abundant is the common
(Morning Glory Convolvulus septum.) The flowers are
large and white. It is without odor nor has it any path-find-
ers. It opens during the early morning and is not abund-
antly visited by insects. Hermann Mueller states that on
dark evenings he found it closed between 9 and 10 o’clock,
but open on moonlight evenings. Its distribution in Europe
is supposed to be-dependant on Sphinx Convolvuli but Muel-
ler records a number of other visitors and Robertson reports
a number of Apidae.
The C. arvensis has become a common weed in places.
It has a funnel-shaped, white or red corolla with a yellow
base on the inside and five radiating white streaks which are
the path-finders. The flower closes in the evening and rainy
weather and is therefore adapted to diurnal insects.83
The Ipomoea testigridis L. has cieistogamous flowers.
This is said to be true also of some members of the genus.
Cuscuta. The I. batatas, or Sweet Potato, seldom flowers.
The members of this order are adapted to a
Sotanaceae. var;on8 C1 ass of visitors. The large-flowered
species of Datura are adapted to Sphingidae and especially
to the humming bird. In Solatium tuberosum and S. nigrum
the flowers do not secrete nectar but are visited solely for
their pollen. In S tuberosum the five anthers meet to form a
cone and surr mnd the style. The anthers begin to dehisce
at their apex and when touched the pollen falls out. Mr.
Robertson has observed females of Bombus americanorum col-
lecting the pollen.
Datura Stramonium. The Jamestown Weed is a tall
(O-irse weed with a white corolla about three inches long and
FIG. 33.
Fig-. 83. II. Datura flower visited by hamming bird; three-fourths natural
size. Left hand figure. Heiothrix aurita, three-fourths natural size. Right
hand figure, Heliactinus cumulus, three-fourths natural size. I. Sword beak
Docimaste* emsifer. (After Brehm. from Behrens’ text book.)84
stamens adherent to the corolla tube fora part of the distance
then leading inwards, thus effectually excluding bees from
the honey so that only Sphingidae can obtain it. Mr.
Robertson reports that honey bees remove the pollen as soon
as the flower is open, before the flight of Deilephila lineata.
A Venezuelan species of Datura is visited by Docimastes eti-
sifer, the female of which has a beak 8 cm long, and the
male one 10 cm. in length, these corresponding to the tube
of the corolla.
Nicotiana alata. This commonly cultivated plant is
clammy pubescent with a large white corolla, a long and
nearly cylindrical tube, 5-6 cm. long, with a limb deeply
five cleft. The stamens are inserted on the tube and includ-
ed; the stigma partially blocks the passage way. The flow-
ers are open during the night and are delightfully fragrant.
Here at Ames it is abundantly visited by Sphingidae.
Schizanthus pinnatus. This plant is now commonly cul-
tivated in gardens. Its flowers are irregular, two-lipped.
The upper lip is made up of five parts, variously colored and
spotted with yellow and purple, a narrow groove leads to the
nectar. The under lobe of the smaller lip is more or less
hooded and sack-like. When the insect settles upon the low-
er lip it springs up and the pollen is thrown out for a consid-
erable distance. The stamens are held in the tube of the
lower lip.
„ .	. ,	The members of this order show var-
Schroplmlarmceae.
ious adaptations to insect visitors.
Some of the species have corollas regular or nearly so, as in
Veronica. These are adapted to flies and bees. Secondly in
Scrophularia, the flowers are dull in color with a wide open
mouth and nectar easily accessible and Antirrhinum and
Linaria with the nectar protected, pollinated by large bees.85
In Pedicularis the tubes are narrow; the upper lip pro-
tects the anthers while the lower lip serves as a landing place.
As to colors the flowers are various, even in closely related
species of the same genus, as in Pedicularis and especially
in Castilleia.
Scrophularia nodosa L. var. Md‘ ilandica Gray. Prof.
Trelease has given us an interesting account of the pollination
of this plant. It is especially adapted to wasps. Mueller re-
cords 6 Vetpidae. He says:	“The fact that they hold a pro-
portion of over one-third in the list of Scrophularia is suffi-
cient evidence that the flower especially favors wasps. I
know of no bee-flower on which so many wasps occur as in-
truders.” It is frequently visited by hive-bees.
The small, greenish-purple, irregular flowers are proter-
ogynous. In its earlier stages the stigma only protrudes, it
FIG. 34.
Fie. 34. Scrophularia nodosa var Marilandica.	420, 421, early flower pistil
mature. 422, flower a day or two later, pistil flabby, stamens mature. (After
Gray).
is inclined over the lobe. Honey bees and wasps which
largely pollinate the flowers, approach them from the front,
come in contact with the stigma leaving some of the pollen
on it. The following day the stamens come in view and the
style becomes flabby and rests on the lower lip. An insect86
in going to the flower for the nectar is dusted witli pollen
from the later flowers. Self-pollination cannot occur.
Snap dragon (Antirrhinum majus). The flowers are
borne in a raceme and the purple, brown and yellow corollas
are very conspicuous. It is pollinated by bumble bees that
are sufficiently strong to force the upper lip back. The
honey is secreted at the base of the ovary.
This plant differs from common Toadflax in its much
larger flowers into which bumble bees can enter bodily, and
also by its firmly closed corolla which excludes the smaller
bees. The nectar is secreted by the smooth, green fleshy
base of the ovary.
The Yellow Rattle (Rhinanthus. crista galli, L ) which oc-
curs along the New England coast, in the mountains of New
Hampshire, Lake Superior region and northward sheds its
KIG, 35.
Fig, 35. Dehiscence of anthers. 4, anthers not separated; 5, single anther; T.
and 8, Pyrnla necunda showing position of stamens and in the latter how pollen
is shed. The dagger in each case indicates how the insect enters the flower.
(After Kerner von Marilaun.)
pollen in an interesting way on the insect’s head. ‘'Each87
anther lies so close to its opposite neighbor and they dehisce
so widely on their opposed faces that both together form one
pollen reservoir.” They are closed together by the hairs on
the edges of the anthers. The filaments are rigid. At their
bases the anterior pair is set close together and provided with
sharp points on their inner sides but a short distance below
the anthers they are smooth and wide enough apart to admit
the head of an insect. When the bee’s tongue is pushed in,
the filaments are forced apart, the anther cells are tom and
the pollen falls on the insect,.
Yellow Rattle produces two kinds of flowers, one con-
spicuous and unable to be self-fertilized, the other conspicu-
ous and regularly self-fertilized.
For a general synopsis of the Labiateae, a pa-
Labiateae. pgr by Robertson and Hermann Mueller’s Ferti-
lization of Flowers should be consulted Robertson says:
“In the case of the UmbeUi/erae, which have very uni-
form flowers, I have been able to show that the preponder-
ance of the bees, lower Hymenoptera or Diptera was deter-
mined mainly by the time of blooming, and the peculiarities
in the lists of visitors were best shown by a table arranging
species in the order of blooming A similar arrangement of
the Labiatae does not give very important results, since the
differences in the lists are mainly due to differences in struc-
ture, and the time of blooming has little influence. In the
case of the Pycnanthernums, there seems to be a plain case of
correlation between the form and arrangement of the flowers
and the time of flight of the lower Hymenoptera, which are
very important visitors. If the flowers bloomed in April the
lower Hymenoptera would be almost entirely wanting, and
the list would consist mainly of bees and flies.
Of the twenty-three species considered in the present88
paper nine show long-tongued bees—Bombus, Synhalonia,
Anthophora and Melissodes — as their principal visitors and
depend mainly upon them. Eight show special adaptation
to bees in general or to shorter-tongued species. Early
FIG. 36.
Fig-. 36. Sage (Salvia glutinnsa). 1 and 2, visited by bumble-beee. 2, style
touching thorax. 1, Anthers touching insect. 3, stamen with long connective,
which connects the sterile anther lying in front ot the opening of the tube of
the corolla, and the fertile anther lying in the arched upper lip. In 4 and 5, the
dagger indicates the point where the insect strikes the hinged sterile anther.
(After Kerner von Marilaun.)89
blooming species are visited by Bombus females, Anthophora,
Synhalonia, Osmia and Alcidamea. Later blooming species
are visited by Bombus males and workers and Melissodes,
while bees of the other genera are wanting.”
Sage. As previously stated, irregularity is one of
the causes that leads to cross-pollination by insects.
One of the most interesting is the pollination in meadow
sage (Salvia pratensis) which was accurately described and
figured by Sprengel. The flowers in this species, as Hilde-
brand has shown, are proterandrous. This pretty blue sage
is common in the meadows of Europe. The blue labiate
flowers are arranged in a raceme. The upper lip is arched.
In their first stage the stigmas are folded together and pro-
trude from the upper lip but later they unfold and point
downward. The opening of the tube of the corolla is guard-
ed by two oblique processes which are the sterile, transform-
ed anthers. Attached to these are extremely long connec-
tives. (In most flowers the connective between anther
cells is short)' The other anther cell is under the arched lip
of the corolla. Now, when a bumble-bee lights on the under
lip and thrusts its proboscis downward into the nectary
which is indicated by the purplish spot, it comes in contact
with the processes which close the throat of the corolla.
When they are touched they lift upward and backward and
the fertil anthers concealed under the arched upper lip come
forward and downward, and in this way the pollen is brushed
off on the bee’s back. The bee gets an abundance of nectar
which is found in the lower part of the tube, and secreted by
the yellow, fleshy portion underneath the ovary.
In 8. lanceolata, which has become not uncommon in
some parts of Iowa, the blue flowers are conspicuous. The
lip forms a landing place for insects. The style extends be-90
yond the upper lip and is curved up and the anthers have
the same adaptation as in other species. The connective blocks
the passage way and as the insect thrusts its proboscis into
the flower the other anther comes over its back.
Salvia sclarea, S. aethiopica, and S. glutinosa have a simi-
lar arrangement for pollination. When the insect visits an
older salvia flower and is about to enter, some of the pol-
1 m is left on the stigma. Figure 33 pg. 88 shows an excellent
likeness of Salvia glntinosa. In lopezias (Lopezia coronata, etc.)
the pollen comes to the insect from the lower side. While
some of the salvias are adapted to bumble-bees for pollina-
tion, Prof. Trelease has shown that Salvia splendens and
others are pollinated by humming-birds. The color of
Salvia gesnerifolia is brilliant. Bees cannot get nectar in
the normal way. Lepidoptera, though having a tongue
sufficiently long to get the nectar cannot do so, owing to the
lower ends of the connective, which are dilated. The levers
are stiff enough to prevent butterflies from working it.
Nepeta Cataria. In catnip the flowers are born in
glomerate cymes and are proterandrous. The short corollas
are whitish and spotted. The nectar is accessible to many
short-tongued insects. It is commonly visited by the honey
bee and some species of Bombus as well as some Diptera
and Lepidoptera.
Monarda fistulosa. Horse Mint is a common plant,
growing in our woods and along railroads. It is quite con-
spicuous with numerous branches and flowers in glomerate
heads. The bilabiate corolla is pubescent; the upper lip is
narrow and extends obliquely upwards, containing the
stamens and pistil, the former being attached to the lower lip
of the corolla. Since the anthers and stigma are so far apart
the largest bees are likely only to touch them when landing91
upon it. The nectar is secreted by the fleshy disc below the
ovary and is protected from unbidden guests by small pro-
jections. Mr. Robertson, in speaking of the flower, says.
“The tubes measure 18 to 19 mm., which indicates an
adaptation to long tongues. The form of the tube, the bil-
abiate corolla, and the position of the stamens and style indi-
cate that the flower is a modification of a nototribe flower
originally adapted to bumble-bees. The level-topped heads,
the erect corollas, the exposed organs and the rose color in-
dicate a tendency to suit butterflies, which in fact are the
principal guests.”
Among the insect visitors here at Ames are:	Bymenop-
tera Bombus virginicus, B, pennsylvanicus, Odynerus
foraminatus and Lasius brunneus; Diptera, two species
of the family Bomyplidae; Hemiptera, Phymatus wolfii,
Lygus pratensis, and Calcoris rapidus. In Colorado it is
much visited by several species of the Genus Bombus,
also some Lepidoptera■ In Wyoming where I observed
this species this summer Bombus is also a frequent visitor.
The flowers have a much deeper color especially at an atti-
tude of 5000 feet.
Lamium amplexicaule L. Species of the genus
Lamium are adapted to bumble-bees. Mueller never suc-
ceeded in finding bees in the species here considered. He
says; “But I have found immediately after the opening of
the flower, the tip of the lower stigma standing not above
but below and between the anthers, and dusted with pollen,
no doubt from the same flower.” The purpose of calling
attention to the species here is that the plant has in addition
to the ordinary also clesistogamous flowers. Axell was of
the opinion that the existence of such flowers in this species
was due to a lower tempature which checked the develop-92
ment of the conspicuous flowers and also because insects
failed to pollinate the flowers during bad weather.
FIG. 37.
Fig. 37. CJeistogamou.s flower of
Lamium amplexicaule. (After Lub-
buck).
FIG. 37 A.
Fig. 37 A. Section of cleistogamous
flower of dead nettle (Lamium amplezi-
caule). (After Lubbuck.)
Aristolochiaceae.
Birthwort (Aristolochia clematitis) is an
example of flowers pollinated by small
flies; the arrangement is quite unique. The yellow flowers
are arranged in whorls. The long, tubular flowers consist of
a wide, funnel-shaped throat and a long and narrow tube
which is lined with stiff hairs. The lower part is enlarged
and contains the stamens and part of the pistil. In Aristolo-
chia ringens the calyx has developed a lower and upper lip.
In the birthwort there is a flattened expansion which serves
as a resting place for insects. The colors as well as the disa-
greeable odor make these flowers attractive to certain kinds
of insects. Flies find no difficulty in going into the flower,
since the hairs all point in an oblique direction away from
the opening. When the insect reaches the expansion it is
comfortably housed. The temperature is several degrees
warmer than the surrounding air. They now try to escape,
and in doing so come in contact with the stigma where they
leave some pollen from other flowers, but they cannot es-93
cape since the hairs all point in one direction. The flower
is a trap and the insects are prisoners for one or more days.
Some nourishment is found, but in the course of time the
stamens mature and the anthers dehisce and a large amount
of the pollen drops on the floor of the cavity. This food is
FIG. 38.
Pig-. 38. Bitrhwort (Aristolochia dermatitis). I. Infloresance. II. Transverse
Bection before pollination. III. After pollination, s, throat, r, tube h,
hairs, r, expansion of tube of calyx, u, stigma, a, anthers, b, ovary. (Aft-
er Behrens.)
welcomed by the insects but they soon become restless and
in their endeavor to escape become dusted with pollen. The
time has about arrived for the insects to be liberated. The
hairs wither and now the insects can escape; at the same time
the peduncle bends over so that the flowers drop. The
prisoners escape, go to the younger flower, leave some pol-
len on the stigma and when the stamens dehisce, after im-
prisonment, are liberated again.
Elaeagnus angustifolia. This beautiful
Elaeagaaceae. European shrub is related to our north-
western Buffalo Berry (Elaeagnus argmtea Pursh.) It has94
perfect flowers. The calyx gamosepalus; the outer part of
the tube and the lobes are silvery scurfy, the inner at first
greenish yellow, later becoming lemon yellow. The flowers
are not conspicuous though the odor is decidedly attractive
and pleasant, the air being scented for some distance. Stam-
ens four, somewhat shorter than the pistil, both maturing at
the same time. The nectar is secreted from a large fleshy
gland at the lower end of the style in the bottom of the cal-
yx tube. It is much visited by the honey-bee and Bombus.
The pollination of fig (Ficus carica) is just
Urticaceae. ag remarkable as that of the Yucca.	Since
ancient times artificial pollination or caprification was affect-
ed by the Caprifieus. This was done by hanging ripe fruit
of the Caprifieus to the branches of the fig tree “whose figs
are then in their female stage with open ostiola.” The wasps
issue from the Caprifieus, enter the fig and bring pollen of
the former. In order to fully understand the method of
pollination we should study the structure of the flowers. A
fig is not a single ripened fruit, but a branch in which there
are a large number of fruits. In some species as Ficus
pumila female flowers only occur in the bottom of the urn,
while the pollen bearing flowers occur around the opening.
In Ficus carica two kinds of plants occur; Caprifieus
which bear on the inner wall a large number of female
flowers, which are later formed into galls. The male flowers
which line the opening do not mature till the insects are
hatched. The second kind only bear figs, Ficus■ The galls
in the caprifieus are formed in this way. A small chalcid
wasp (Blastophaga grossorum) enters the urn through the
ostiolum and its ovipositor is thrust vertically in the style of
the flower. It deposits its eggs in the ovary of the female
flowers between the nucleus and the integuments placing one95
FIG. 39.
Fig. 39. Transport of pollen by insects laying eggs in ovary. 1, Yucca (Y.
Whipplti). 2, A single opened flower with iesect Pronuba yuccasella, 3, Stigma
of the same. 4. The insect flying to the flower. 5, Head of the Pronuba with a
ball of pollen from the flower. 6, Ficus pumUa. 7, A single flower taken from
lower part of the urn of the same species. 8-9, Stamens, upper part of the urn.
10. Ficus carica (common fig) with galls of Blast*iphaga. 11. Same with fertile
flowers showing wasps. 12, Staminateflowers. 13. Pistillate flower with long
style 14, One of the pistils developed into gall. 15, Inject coming from gall.
(After Kerner von Marilaun.).96
egg, only, in each. The small white larvae grow rapidly
and cause the wall of the ovary to develop, and in conse-
quence the seed does not form, but the fruit develops into a
gall. When the insects are mature they leave the galls, the
wingless male first; the females remain somewhat longer.
After leaving the ovary they are fertilized by the male. They
do not tarry long in the urn. In going out by way of the
ostiolum they come in contact with the pollen which is dust-
ed over their whole body. They allow their wings to dry,
and then run to another urn, either on the same plant or
another. In entering a new urn their wings are injured or
broken off. They leave some of the pollen on the stigmas
and when these are in the perfect flowers, seed is developed;
but when imperfect, as in those which produce galls, fertili-
zation does not occur. It has been observed that although
the insect deposits its eggs in the perfect flowers, in Ficus
carica they will not develop, since the ovipositor is so short
that it cannot reach the ovule. The caprificus becomes hard
and withers on the tree, its only use being to produce pollen.
The fruit of the fig tree Ficus becomes sweet and juicy
when the seed ripens. The pollination of all species of
Ficus have not been studied although for the 600 species de-
scribed there are at least fifty species of small wasps belong-
in to the genera Blastophoga, Crossogaster, Sycophaga
and Tetrapus, which carry pollen from one urn to another.
One species, Blastophaga brasiliensis, has been found on
seven different species of fig tree. Figs will also develop
without caprification.
The willow flower is simple in its structure
Saiicaceae. aD(j .g u8ua]]y dioecious. The anthers of
the staminate flowers usually have some decided color The
flowers are massed in catkins and open out before the leaves97
appear, as is usual with anemophilous plants. They have
an abundance of nectar, which, in the early flowering
periods, leads many insects to go to it. They also have a
decided odor. The staminate flowers are more conspicuous
than the pistillate, especially in Salix nigra.
Each flower consists of a small bract, with the sta-
mens. one or more, to the inside. These are accompanied
by one or two small nectar glands. In the pistillate flower
the stamens are replaced by the pistil and a nectar gland.
The willow is one of the lowest of the entomophilous plants.
It is visited by a variety of insects. The honey bee, bumble
bee Andrena, and other Hymenoptera visit it, as also do
flies (.Bombylius), butterflies ( Vanessa), and beetles. The
Andrnas are common visitors; the head and thorax of
these insects are provided with hairs and as the insects take
the nectar from the staminate flowers the pollen grains ad-
here to the bristles and then as they go to the pistillate
flowers for nectar some of the pollen is left on the stigma.
The petioles of some of our willows are provided with
glands. Salix laurifolia has so many of these glands
that the tree has a decided odor. These glands are no doubt
for protection.
Darwin, in the introduction to his classic
Orcliidaceae.
work, t;On the Fertilization of Orchids by
Insects” says:	“As orchards are universally acknowledged
to rank amongst the most singular and most modified forms
in the vegetable kingdom, I have thought that the facts to
be given might lead some observers to look more curiously
into the hadits of our several native species. An examina-
tion of their many beautiful contrivances will exalt the
whole vegetable kingdom in most persons’ estimation.”
Earlier Sprengel observed that insects were necessary to98
remove the pollen masses, and Waetcher, who seems not to
have been acquainted with Sprengel's work, stated that in-
sects are necessary for the pollination of orchids. Orchids
have been the objects of a large number of interesting pa-
pers. The order is represented by more than three thousand
species. Few of our native species compare in beauty with
those of the tropics. In habit they are extremely diverse.
Hermann Mueller says:	“I do not doubt that orchids owe
their extraodinarily perfect adaptation to particular insects
not only to the tendency of the parts of their flowers to vari-
ation, but also to the separation in time of the two stages in
the act of impregnation. The extremely complete adapta-
tion to cross-fertilization have in their turn resulted, in many
cases, in the flowers becoming absolutely sterile to their own
pollen.”
It may take days, weeks, or even months for the pollen-
tube to reach the ovule and cause impregnation. It may be
interesting to observe that the period of flowering as in many
cases extended over a considerable length of time.
Orchids differ in regard to their capacity for self fertil-
ization; some have cleistogamous flowers, as in Cattleya
and Epidendrum'i some are self-pollinated, or at least oc-
casionally so, frequently in Neottia nidus-avis', others are
never self pollinated although when their own pollen is ap-
plied artificially it is fertile, while some are absolutely ster-
ile to their own pollen though fertile to pollen from another
plant of the same species or to the pollen from a plant of
another species. In some cases the pollen of a plant acts as
a poison when applied to its own stigma.
In older to fully understand the mechanism for the
pollination it will be necessary to give the parts of an orchid
flower. The perianth consists of six parts in two sets; the99
three outer, known ns the sepals, are generally colored.
The petals consist of the three parts one of which the
upper is larger than the others and occurs on the lower side,
this is known as the labellum and is often produced into a
spur-like nectary. In front of the labellum occurs the
stamen which is united with the pistil. In Cypripedium
there are two stamens with the rudiment of a third. The
anther has two very distinct cells; the pollen coheres in
masses, each of which has a stalk; these masses with their
stalks are known as the pollinia. In the genus Cypripe-
dium, the pollen is granular. The ovary is produced above
the perianth and rises up in the middle of the flower as a
column. The stigma is broad and lutingous. The rostel-
lum is a mortified stigma; a part of this is removed with the
pollen masses and is called the viscid disc.
^,In Cypripedium pubescens, which occurs in rich
woods, is offered an interesting object for study. Lady’s
slipper or moccasin flower, of which there are several
species in Iowa, has three spreading sepals; two of them are
usually united into one under the lip. The labellum is ar-
ranged into a kind of moccasin, hence the common name,
Lady'’s Slipper or Moccasin Flower. The edges are recurv-
ed or over-arched. The stamens and pistil are united. We
have a peculiar shield-like body which is notched or hollow-
ed out, and two fertile anthers. The pollen is not united in
pollina. The surface of the stigma is beset with numerous
sharp pointed papillae wrhich are for the purpose of holding
the pollen.
Insects are attracted by the color and strong odor and
find it an easy matter to get into the flower, but they ex-
perience some trouble in getting out the way they entered,
since the margin of the lip is rolled in. Prof. Trelease was100
the first to call attention to the fact that in some of our
Oypripediums a portion near the upper end of the inflated
sac in transparent, serving as a window. An insect would
naturally make for the light, and since this window is near
the small opening the insect goes out. It gets some of the
pollen on its head as it comes in contact with the varnished
FIG. 40.
Fig 40. 1, European lady’s slipper (Cypripedium calceolus); on the left hand
side an insect, Andrena going out of the flower with pollen adhering to its
back; 2, sectional side view of same; 3, an Andrena. (Kerner von Mirilaun).
film of the pollen. Some nectar is found on the hairs
in bottom of labellum. Now, when the insect flies to an-
other flower and enters by the large opening, it cannot fail
to get some of the pollen from its head, against the large
stigma which partially blocks the passage way. Dr. Gray-
says:	“The stigma of every other orchid is smooth and
glutinous; this is merely moist and finely roughened; the
roughness comes from very minute projections all pointing
forward so that the surface may be likened to a wool-card101
or rasp.” I have observed these windows in several of our
species—small white lady’s slipper (Cypripedium candi-
dum) large yellow (C- pubescens) and perhaps also occur-
ring in other species.
Mueller thus describes the insect’s method of going out
and in:	“These bees, attracted bv the color and perfume
of the flower, fly into the slipper shaped lip and lick and
bite the hairs lining its floor, which are sometimes covered
with small drops of honey. They try for some time to es-
cape by climbing up the vaulted sides of their prison toward
the orifice that they entered by; at last, after creeping be-
neath the stigma; they manage with a great offort to escape
by one of two small lateral openings at the base of the lip;
in doing so they smear one shoulder with a sticky pollen
from the anther immediately above. In the next flower, the
bee, as it creeps under the stigma, leaves some pollen on its
papillae, which are long and point obliquely forwards; then,
squeezing itself again through one of the small orifices, it
acquires another load of pollen; cross-fertilization is thus ef-
fected regularly.” He found chiefly Andrena.
Delpino believes the C. barbatum is pollinated by flies
and that C. caudatum is pollinated by snails. Weed states
that he found Halictm pollinating flowers of C. acaule, the
Pink Lady’s slipper. The pollination of this species is de-
scribed by him as follows:	“The most striking part of the
latter (the blossom) is the pouch-shaped labellum, projecting
forwards and downwards. This curiously shaped organ con-
sists of a large inflated sac, with the front edges inflected in
such a way as to form a slit-like opening.”
“The inside of the bottom of the labellum is furnished
with hairs projecting upward and backward. Many of them
are tipped with a glutinous secretion, which is believed to be102
eaten by the insect visitors. No other signs of nectar are to
be seen.”
“Sometimes one will fine a dead bumble bee in the Moc-
casin flower. It has gone in through the large opening of
the labellmn, has been unable to escape the way it came, and
crawling upward, becomes imprisoned beneath the stigma,
where it finally dies.”
Greater Green Orchis (Habenaria orbiculata).—Dr.
Gray gives the following account of the pollination in this
species:	The three external parts of the perianth, the sepals,
are much broader than the three internal, the petals. The
FIG. 41.
Fig. 41. Hawk moth (Sphynix drupiferarvm) with two pollinia, one attached
to each eye from Habenaria orbiculata, as it comes from the flower. The long
tongue partially uncoiled. The figure to the right shows the deflexed pollinia
and the coiled tongue in the center. (After Gray.)
base of the long and narrow petal is turned downward and
hollowed out into a long tube, which is closed at the bottom
and open at the top. This is the spur or nectary, and con-
tains the nectar which is secreted in it. The single anther
and stigma are united and lie just beyond the opening of the
nectary. The anther cells open by a long chink, approach-103
ingeach others at the upper end, while the lower is widely
separated and the space between is very glutinous. The
PIG. 43 A.
Fig. 42 A. Polliiiia and pollen
grains of orchid (Habenaria or-
biculata). 464, five separate pollen
packets; the figure below more
magnified, showing pollen grains;
the figure to the left shows a pol-
len mass and stalk, at the base a
gland. (After Gray.)
FIG. 42.
Fig. 42. Flower of Habenaria orbiculata,
46 , stamen and stigma more magnified; 462,
one of the two pollen masses. (After Gray.)104
pollen grains are united by fine threads, then into larger,
finally forming pellets, and having a stalk attacked to a cen-
tral stalk. At the lower end of this stalk is attached a but-
ton-shaped disc, the face of which is exposed and is on a line
with the surface of the anther, so that these two discs look
toward each other across the broad, intervening stigmatic
space. When a finger or any small body touches these discs
they adhere so firmly that the attached pollinia or pollen
masses are dragged out of the cell and carried away entire.
When a hawk-moth like Sphynx drupifearum visits these
flowers and presses its head into the center of the flower to
get the nectar out of the nectary a pollen mass will be fixed
to each eye, and on withdrawal these will stand as shown in
figure.
But they are soon turned downward as shown to the right.
This is due not to their own weight but to a contraction in
the drying of one side of the fleshy piece which connects the
disc with the stalk. When the moth passes from one flower
to that of another plant, and thrusts its proboscis down to
get the nectar the pollen masses on the insect will be brought
in contact with the large viscid stigma; either some of the
pellets will be left on the stigma or a whole pollen mass.”
Cata setum- This is interesting as regards its pollina-
tion. It is hot uncommon now in greenhouses. Its remark-
able adoption was first pointed out by Darwin. In this
orchid the pollina and stigmas are in different flowers. Like
Habenaria the pollinun is furnished with a viscid disc, but
in this case the insect does not touch the viscid disc. The
flower is sensitive and throws the pollinium at the insect. Sir
John Lubbock says that Darwin irritated one of the flowers
in his presence and the pollinium was thrown nearly three
feet In a staminate flower the pollinum, which is in a state of105
FIG. 43.
Fig. 43, Cata8etum\ an, antennae; 1, labellum; po, pollinium. (After Darwin.)106
tenison, is curved, and held in a position by a delicate mem-
brane. Insects light on the lower lip of the flower. In front
of this lip are two processes known as antennae. In Cata-
setum saccatum only one arm is sensitive; in some species
both are sensitive. When the insect touches the left hand
one, the excitement is conveyed along it, the membrane re
taining the pollinium is ruptured, the latter released and
thrown with considerable force with the viscid disc foremost,
and in such a direction as to come in contact with the head of
the insect. When the insect visits another plant containing
the pistil it leaves some of the pollen on the stigma.
The Angraecum sesquipedale is a native of Madagas-
car. The spur in this species is longer than of any other orchid.
It varies from 10 to over 14 inches in length. It is said, ac-
cording to Darwin, than an insect must have a tongue 11 to
12 inches long in order to reach the nectar.
Darwin, in the following words, says:	“It is, however,
surprising that any insect should be able to reach the nectar.
Our English Sphinxes have proboscides as long as their
bodies; but in Madagascar their must be moths with probo-
scides capable of extension to a length of between 10 and 11
inches. This belief of mine has been ridiculed by some ento-
mologists, but we now know from Fritz Mueller that there is
a sphinx-moth in South Brazil which has a procoscis of nearly
sufficient length, for when dried it was between ten and
eleven inches long. When not protruded it is coiled up into
a spiral of at least twenty windings-”
Mr. Forbes has found a moth in Madagascar with a
tongue Tong enough to reach the nectar.
A green, whip-like nectary hangs down beneath the la-
bellum. According to Darwin only the lower one and one-
half inches, in the species he examined, as filled with nectar.107
I have seen some that were between 12 and 14 inches in
length.
Spiranthes■ Flowers white and very fragrant. The
parts of the perianth are so disposed as to limit insects from
obtaining the nectar. Mr. Robertson describes it for Spir-
anihes gracilis as follows:	“The upper sepal is connivent
with the two upper petals, forming the upper wall of the tube.
At the free end these part from a three-toothed upper lip.
This is too small to form a landing place for insects, but
makes the flower a little more conspicuous. A proboscis
about four millimeters long can drain the nectar with ease.
At Orlando, Florida, I saw them visited bv a bee which I
failed to capture, but which I supposod was Anthidium not-
atum, Latr., and by Megachile brevis Say.
The last mentioned insects had two discs with attached
pollinia fastened to the maxillary laminae, and I think this
is the particular part of a bee to which the flower is adapted
to fasten its pollinia.
But the most important consideration is that when the
bee's proboscis is folded up under the head, the maxillary
laminae fall into such a position that the pollinia retain their
hold without danger of being disturbed.”
In the Flower-de-Luce (Iris versicolor, L ) the
Iridacae. perjanth is made up of six parts of violet blue
color and purple-veined. The three outer divisions are re-
flexed; the three inner are smaller and erect. There are
three stamens, one on each side of the stigma; back of each
stamen and partly overhanging it is a peculiar petal-like body
—the style, the stigma occurs as a thin lip under the apex.
Stigma and stamens are protected; the former is larger than
the latter; the anther discharges its pollen through a long
opening away from the stigma An insect alights on the ex-108
paneled petal and, guided by the hairs, obtains the nect&r,
and in doing so brushes against the stigma where it leaves
some of the pollen, from another flower. It is visited by
bumble bees, Syrphus flies, also butterflies, which, however
are not normal pollinators.
The order is separated into several very diatlnct
Li 1
groups; in some the nectar is easily accessible,
others, as the tulips, are without nectar. Species of Allium
are visited by a miscellaneous lot of visitors Lilium With a
FIG. 45.
Fig-. 45. Pronuba, from larva to adult. (After Riley),
narrow groove is adapted to Lepidoptera, nocturnal and
diurnal.
Wild Yellow Lily. The Lilium Canadensis, L., is com-
mon in our northern swamps. The flowers are pendulous,
the perianth consists of six parts, yelloWish-orange With
brown spots. The nectary occurs in the form of a groove in
the middle of each division of the perianth. The six stamens
have their linear anthers extrorsely attached near the middle
finally becoming versatile. The style is elongated and some-
what club shaped; the stigma three lobed. It is pollinated
by Hymenoptera. Mr. Weed records Megachile, but I have
observed Trochilus. The Lilium Mortagon is pollinated by
Sphingidae.109
Yucca■ The glorious yuccas are native American plants
occurring most commonly in the dry, sandy regions of the
southwest. Spanish dagger or Spanish bayonet (.Yucca
ungustifolia) occurs in the loess region on the Missouri river
in the western part of Iowa. Drs. C. V. Riley and George
Engleman have made some interesting and valuable observa-
tions on the method of pollination in this species. Prof
Trelease and Mr. Webber have substantiated their work. In
Yuccas the relation between the flower and a yucca moth is
very close. The pendant, more or less bell shaped flowers
are borne in mostly simple racemes having a perianth of three
sepals and three petals, yellowish white in color and very
fragrant. Both color and odor make them conspicuous for
FIG. 48.
Pig. 46. Moth collecting pollen. (After Riley).
night-flying insects. The viscid pollen is contained in small
anthers which arise from the papillose, curved filaments. A110
flower remains open for a single day, on the second day the
ends of the six stamens begin to close up and the flower has
the shape of a balloon with six small openings. At twilight
and during the night, there is flying about the flowers of the
yucca a yellowish white moth with a metallic luster, the
Pronuba yuccasella. The first joint of the maxillae is extraor-
dinarily lengthened, and on the inner side it is provided with
8tift bristles. It can be rolled up as a proboscis. This struc-
ture is for the purpose of collecting, rolling up and holding
FIG. 48.
Fig, 48. Moth with a ball of pollen* (After Riley).
the pollen. The females of the moth enter the open flower
and obtain the pollen, not however to eat, but to carry
it to another flower. In a short time the moth has col-Ill
lected a ball of pollen which it holds on the under side of
the head by the maxillae. It appears like a large craw. It
is sometimes three times as large as the head of the insect. It
immediately leaves the flower to search another. It now de-
posits its eggs in the side of the ovary. The ovipositor con-
sists of four horny bristles pressed together which is well
adapted for boring the tissues of the ovary. After the
eggs are deposited the moth runs to the hollow funnel shap-
ed stigma, she then rolls up her proboscis-like mandibles and
places the pollen on the stigmas. The eggs hatch on the
fourth or fifth day Each larva requires from 18 to 20 seeds
for its development. When mature it bites a hole through
the fleshy wall and reaches the ground by means of a thread,
enters the soil and forms an egg shaped cocoon. It remains
in this stage till the following summer. About fourteen days
before the flowering time of yucca it pupates and when the
flowers open, tiny moths issue from the pupa. The pollina-
tion of yucca is an extraordinary case. Without the yucca
moth the viscid pollen could not reach the stigma. If the
yucca moth is excluded seed will not develop Yucca angust-
folia and Y. Whipplei, when grown in Europe have never de-
veloped a single seed.
Dr. Riley says:	“Upon a superficial view this little
moth shows nothing very peculiar. The general coloration
is white, the primaries being purely white on the upper sur-
face, so that when at rest in the half-open flowers of the
Yucca it is not easily detected. The under surfaces, how-
ever, are dusky and oflset in flight the whiteness of the rest
of the body, so as to render the species somewhat difficult
of detection while flitting from plant to plant. The male
shows no very marked peculiarities to distinguish it from the
other members of the family, the most noticeable being,112
perhaps, the prominence of the exposed portions of the
genitalia. The female, however, shows some remarkable
structural peculiarities, which admirably adapt her for the
functions she has to perform, for she must fertilize the plant,
for her larvae feed upon the seeds.”
“Her activity begins soon after dark, but consists, at
first, in assiduouslv collecting a load of pollen. She may be
seen running up to the top of one of the stamens and bend-
ing her head down over the anther, stretching the maxillary
tentacles, so wonderfully modified for the purpose, to their
fullest extent, the tongue uncoiled and reaching to the
opposite side of the stamen, while the head is kept close to
the anther and moved peculiarly back and forth something
as in the motion of a caterpillar when feeding. The maxil-
lary palpi are used in this act very much as the ordinary
mandibles are used in other insects, removing or scraping
the pollen toward the tentacles. After thus gathering the
pollen she raises her head and commences to shape into a
little mass or pellet by using her front legs, very much as a
cat does when cleansing her mouth, some times using only
one leg, at another time both, smoothing and pressing the
gathered pollen, the tentacles meanwhile stretching and
curving. After collecting all the pollen from one anther
she proceeds to another and repeats the operation, then to a
third and fourth, after which, with her relatively large load
—often twice as large as the head—held firmly against the
neck and front trochanters, she usually runs about or flies to
another plant; for I have often noticed that oviposition, as a
rule, is accomplished in some other flower than that from
which the pollen was gathered, and that cross fertilization is
thus secured.”113
The Aroids have some interesting points in their
i4raceae. p0]ljnatj0n. Some of the species are dull in
color as our Jack-in the Pulpit.
Avoids. In Arum maoulation The “ flower” con-
sists of a green leaf called the spathe which contains a central
portion, the spadix, that bears the flowers. The pistils are
near the base, while the stamens are higher up. Lubbock
says:	“Now in this case nothing would at first sight seem
easier or more natural than that the pollen from the anthers
should fall on and fertilize the pistils.” In this case the
stigmas mature before the pistil — proterogynous. Small
flies (several hundred have been found in a single flower),
which are attracted by the showy spad/fxTenter the flower and
and are imprisoned by the stiff hairs which line the spathe.
They have, however, left some pollen on the ripe stigmas.
After the period of maturity has passed, each stigma secretes
some nectar which repays the insect. The stamens then
dehisce, the pollen drops to the bottom of the cavity, and the
insects become covered with pollen. The hairs on the spathe
now shrivel up and the insects are released. In Arum
concephaloides the structure of the inflorescence is some-
what similar. The insects seek shelter in the “flowers,”
whieh are somewhat warmer than the surrounding atmos-
phere —30_2_to36 ° Cent., while in Arum Italicum the
temperature has been observed at 44 ° Cent. The flowers of
this and other aroids have a disagreeable odor, not unlike
that of decomposing urine. It therefore attracts insects that
seek such odors, which find the flattened expansion of the
spathe a convenient landing place. In the narrow portion of
the spathe a ring of stiff hairs projects horizontally except the
tips, which bend downward, making a perfect ring. A
second ring occurs just above the pistils. These shrivel up114
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before the upper. When
the lower row is relaxed
the insects remain for a
time on the staminate
flowers and get covered
with pollen. The hairs of
the upper ring also soon
relaxes and the insects es-
cape, and go to a second
plant. Kerner von Mari-
laun records several thous-
and gnats belonging to
the genus Ceratpogon in
one “flower.” In all six.
teen species belonging to
the genera Chironomus,
IAmosina and Sciara■ In
another aroid, Dracuncu-
lus creticus, flies like
Lucilia and common
beetles like Aleochara
fuscipes, etc., occur. More
than 250 common beetles
have been found in a single
flower of the Italian Dra-
cunculus vulgaris-
Jack - in ■ the -Pulpit.
The large spathe is
arched over the central
column, the spadix; below
the edges overlap. The
spadix contains the flow-
ers, mostly one kind, but
also monoecious. It is115
visited by small insects, the fungus gnats. The insects find
their way in between spadix and spathe, the projection on
the spadix prevents the insect from getting out above. In-
sects can find their way out where the edges of the spathe
overlap, and Weed thinks that in older flowers the walls open
wider, at any rate, in many cases gnats perish in the prison
chamber.
The Skunk Cabbage (Symplocarpus foetidus) has not
only a disagreeable odor, but also color. It grows in
swampy places and is visited by numerous flies that breed
in these marshy places.
Colocasia odora• Some of the aroids are pollinated
by snails. Delpino states that this species is pollinated
in this way. Mueller says:	“The spadix is covered
in its whole length with normal and abortive stamens
and pistils; only female flowers occur in the lower, wider
part of the spathe, and they only are mature in the
first period. From this chamber an attractive odor
issues, and the snails are admitted by a narrow en-
trance. In the second stage this entrance closes, and the
anthers dehisce. Snails which creep onto the flower in this
stage seek vainly for the entrance, and dust themselves with
pollen, which they afterwards carry to the stigmas of
younger plants. Delpino supposes that the snails after
affecting cross fertilization, are poisoned by an irritant
secretion within the chamber of tde spathe, and are so pre-
vented from devouring the flowers.”CHAPTER VI.
FLOWERS AND THEIR UNBIDDEN GUESTS.
It is a matter of very common
Perforation of Flowers. ,	,.	*.	„
observation that many of our flow-
ers are perforated, and that insects obtain nectar without
going to the proper sources. The beautiful colors and ex-
quisite contrivanceSuire-reademPmbperative because ofThese"
perforations. The subject has been treated by Darwin 1
and others2. Mr. Jack3 has also recently contributed a
short note on this subject in which he cites a number of
interesting cases. The chief perforators are bumble bees
(Bombus), carpenter bees (Xylocopa) and wasps ( Vespa-)
Hive bees and birds have also been observed. Why should
insects perforate flowers ? Darwin believes that, as a gen-
eral rule, flowers are only perforated when they grow in
large quantities close together; for he found in a gardeu
where Stachys cocdnea and Pentstemon argutus were
growing in large numbers, every flower was perforated, but
at some distance from these was a small stock of Stachys
cocdnea the flowers of which were much scratched, show-
ing that they had been visited by bees, although not a single
flower was perforated. The same thing was noticed on a
small stock of Pentstemon, growing in the same garden.
1	Cross aud self-fertilization. Mueller, L. C., etc.
2	L. H. Pammel; Trans., St. Louis Academy of Science, vol. X, pp. 246-277*
A biblography is given in this paper.
3	Garden and Forest. Vol. V; p. 29.117
The same fact holds true in Trifolium pratense when grow-
ing in fields, and Phaseolus multiform when grown in
large and conspicuous clusters in gardens. It is a well-
known fact that alpine flowers grow in much larger masses
than plants of lower regions. Familiar examples of our
flora are afforded by Silene acaulis, Arenaria, Groelan-
dica, Bryanthus taxifolius, Trifolium sp., Ledum, etc.
Mueller has shown of alpine and'subalpine plants that more
were visited in the Alps than in the lowlands and also that
more species were perforated as is well shown by the list of
flowers which Bombus mastrucatus visits.
Flowers grown in large masses are conspicuous, and
therefore attract many insects ; and, as the perforated flowers
usually contain considerable nectar, the number of insects
visiting the flowers at any one time is very large, and, as
Darwin has shown. Some of the nectaries are sucked dry;
now, in order to save time, for the flowers would have to be
probed for their nectar, the insect makes perforations. To
this rule there are exceptions, as has been shown in some of
the cases cited, where an insect, unable to get a nectar in a
normal way, takes to perforating flowers. Mueller and
others have shown that there is a certain correlation between
the length of the tongues of Rymenoptera and the flowers
they perforate, as can be seen by consulting their tables on
\tiowers and their visitors.
How Flowers are Protected. We have briefly called
attention to a few of the agents which destroy flowers. It is
equally interesting to study the contrivances which protect
the flowers from unbidden guests. Darwin has well said in
a prefatory letter to Dr. Wm. Ogle’s translation of Kerner’s
admirable book on “flowers and their unbidden guests:”
“ The beauty and poet$|y of flowers will not be at all lessened118
to tiie general observer by bis being led through Kerner’s
investigation to notice various small and apparently quite
unimportant details of structure, such as the presence of
FIG. 60.
Fig. 50. Serratula lyc>pif- lia protected by the gummy involucre against a beetle
(Uzythyrea funesta) and ants (Formica). (.After Keruer von Marilaun).
differently directed hairs, viscid glands, etc . which prevent
the access of certain insects and not of others.’’1 s.
119
Were it not for the connivances in many flowers, very
unwelcome guests would often enter the flower and utilize for
themselves what legitimate visitors should have. Flowers
are protected from unbidden guests in various wavs.
1.	Aquatic plants are protected by their isolation in
water. Land plants have occasionally secured for themselves
the same advantages in that certain leaves form cups around
the stem. In others there is a leaf-cup at each joint, while in
some there is a single basin formed of the rosette of leaves at
the base. In these rain and dew not only collect, but are
retained for a considerable time, as in Dipsacus sylvestris,
D laciniatus and Silphium perfoliatum,
2.	By means of slippery leaves, which often have a
curved surface, over which it is impossible for ants to climb,
e■ g., in Gentiana firma. In Cyclamen the reflexed lobes
of the corolla are turned upwards, so that ants cannot crawl
over them.
3.	Plants, and especially parts near the corolla, are
covered with hairs and spines ; these often point downwards,
as in flowers of Salvia, Verbena, Linnea and Stachys-
4.	Some plants are especially distinguished by viscid
and glutinous secretions. These occur on the stem in Silene
antirrhina, on the involucral bracts of Grindelia squar-
rosa, on the calyx and stem of Silene noctiflora and on
the young branches of Robinia viscosa, the secreting glands
shriveling up when the flowers are pollinated.
5.	Kerner believes that the milky juices of some plants,
e. g. Lactuca, Asclepias, Euphorbia, Apocynum, Cheli-
donium, etc., serve to keep ants away. In an experiment
he found that an ant, placed on a lettuce leaf, cut the
epidermal tissue with its sharp claws so that the milky juice
exuded, and, hardening, held the ant to the leaf.120
FIG 51.
Fig. 51. Hairs acting against unbidden guests. 1, Arctostaphylos uva-ursl;
2, section of flower of Centranthus ruber, cut lengthwise; 3, cross-section of
flower; 4, part of flower of tulip (T 8ylvestris)-, 5, Cobaea scandens, showing
hairs near base; 6, hairs on pistil of Daphne blagayana; 7, Lonicera alpigend;
8, Vinca herbacea\ 9-10, stamen and pistil of the same. (After Kerner von
Marilaun.)CHAPTER VII.
CROSS AND SELF-FERTILIZATION IN PI.ANTS.
Dr. Gray, in that charming little book,
Cross Fertilization-	™	,	»	u^,
‘ How Plants Behave,” says:	‘Close
fertilization, that is, the fertilization of the seeds by pollen
from the same flower is very close breeding indeed. It is
the next thing to no fertilization at all in plants, that is to
propagation by buds.” From an elaborate series of experi-
ments made by Darwin \ supplemented by the work of
others a, there can no longer be any doubt that cross-fertiliza-
tion is an advantage. Darwin has aptly said, “Nature abhors
perpetual self-fertilization.” l^Since the appearance of Dar-
win’s Fertilization of Orchids manv contributions have been
made to show the exquisite relations between flowers and
insects]/ Most observers agree that the structure of many
flowers is for the purpose of securing cross-fertilization and
to avoid self-fertilization, although there are those who are
unwilling to see the utility in cross-fertilization. Thomas
Meehan 1 2 3, says. “It has never been clear to my mind that
insects are any material aid to plants by the pollination
which they often undoubtedly accomplish. There has been
little to prove that in-an-in, or close breeding, is an injury;
1	Cross and self-fertilization in plants. See also different forms of flowers
in the same species. Fertilization or orchids.
2	Hildebrand: Die geschlechter vertheilung bei den pflanzen, etc.
Mueller: Fertilization of flowers, English translation.
Lubbuck: British wild flowers in relation to insects, etc.
3	On the fertilization^of Cassia marylandica, Proc. Academy of Natural
Sciences. Philadelphia, Aug. 31, 1886, p. 314.122
and it has been asuuined that cross breeding among plants
mustbe a benefit soelly because arrangements for its accom-
plishments exist.”
Long before Darwin’s admirable researches appeared in
print, some observers surmised that cross-fertilization is an
advantage to the plant. Dean Herbert wrote in 1836 4 5:
“I am inclined to think that I have derived advantage from
impregnating the flowers from which I wished to obtain
seeds with pollen from another individual of the same
variety, or at least from another flower rather than its own,
and especially from an individual grown in a different soil
or aspect.”
Koelreuter, Sprengel and Knight had also observed
many facts with reference to cross-fertilization, though they
failed to see the full import of this question in its relation to
plant life.
Dr. Gray 6 says:	-‘When Mr. Darwin announced the
principle that cross-fertilization between the individuals of a
species is the plan of Nature, and is practically so universal
that it fairly sustains his inference that no hermaphrodite
species continually self-fertilized would continue to exist, he
made it clear to all who apprehend and receive the principle
that a series of plants propagated by buds only must have a
weaker hold of life than a series reproduced by seed.”
Darwin6 was the first to place the subject on a scientific
basis by means of a large number of experiments. He says,
“That the injury from the close breeding of animals and
from self-fertilization of plants does not necessarily depend
on any tendency to disease or weakness of constitution, as
4	Henslow: Origin of floral structures.
5	Darwiniana, p 345.
6	Cross and self-fertilization, etc.123
common to the related parents, and only indirectly on their
relationship in so far as they are apt to resemble each other
in all respects, including their sexual nature.” Secondly, it
will depend on a sexual element of the parents. The pro-
genitors having been in some way exposed to different
conditions, having been intercrossed. Thirdly, what Darwin
calls spontaneous variation. Everyone is familiar with the
practice of gardeners to obtain seed from different localities.
The product is undoubtedly better, since the seeds were
grown in soils of very different nature as well as climatic
conditions. It would no doubt be better, as Darwin7 sug-
gests, to sow the seeds raised in different localities in
alternate rows. By crossing there would be a blending of
the whole organization without in any way affecting the
purity of the variety. Darwin made many experiments to
determine the superiority of cross-fertilized plants over self-
fertilized plants. I will give a few illustrations: A plant of
cultivated morning glory {lpomoea purpurea), grown from
carefully selected seed, when ready to flower was protected
with meshes one-tenth of an inch in diameter so that insects
carrying pollen might be excluded. Ten flowers were fer-
tilized with pollen from the same flower (self fertilized).
Ten other flowers on the same plant were crossed (cross-
fertilized) with pollen from a distinct plant. The cross and
self-fertilized plants were placed in damp sand and allowed
to germinate. The two kinds were then placed under the
same conditions. This was done during ten generations.
At the end of the experiment the product of the cross was
superior to the self-fertilized in every respect. In produc-
tiveness of capsules, the ratio of crossed to self-fertilized in
the third generation was at 100-38. It is also noteworthy
7 Cross-fertilization, etc,, p. 28, p. 58, etc.124
that the seeds were as 100-94. In one of the latter genera-
tions of the fifteen first flowers pollinated from their own
pollen, eight dropped off. While out of the fifteen of the
self-pollinated of the cross-feitilized plants, only one dropped
off. The impaired fertility of self-fertilized manifested itself
in producing smaller anthers.
Darwin gives the following very apt illustration as to
the height of self-fertilized plants8 :
“If all men in a country were on an average six feet
high, and there were some families which had been long and
closely interbred, these would be almost dwarfs, their aver-
age height during ten generations being only four feet eight
and one-fourth inches.”
In the case of cabbage Darwin found that cross-
fertilized plants were to the self-fertilized plants in weight
as 100 to 37. When fresh stock was crossed the difference
in weight in offspring was as 1,000 is to 22, showing a gain
of over 350 per cent. Prof. Bailey also records marked
superiority in crossed plants of cabbage. In regard to egg-
plants Bailey says:
“In 1889 several hand crosses were made among egg-
plants. Three fruits matured, and the seeds from them
were grown in 1890. Some two hundred plants were grown,
and they were characterized throughout the season by great
sturdiness aad vigor of growth. They grew more erect and
taller than other plants near by grown from commercial
seeds. They were the finest plants which I had ever seen.
Prof. Munson, of the Maine Agricultural College, grew
some of this crossed stock in 1891, and he told me that it
was better than any commercial stock in his gardens.”
“In extended experiments in the crossing of pumpkins,
squashes and gourds, carried on during several years, in-125
crease in productiveness due to crossing has been marked in
many instances. Marked increase in productiveness has
been obtained from tomato crosses, even when no other re-
sults of crossing could be seen.”
Darwin’s experiments made with tobacco gave equally
positive results. The crossed and self-fertilized plants were
treated in different ways: Firstly, under very close competi-
tion; secondly, greatly crowded in large pots; thirdly, sown
in poor and good ground so as not to he crowded. In each
case the crossed plants were superior in every way. The
crossed seed germinated easier, more rapid growth of the
seedlings while young, and earlier flowering of mature
plants. Ultimately they exceed in height also. The
superiority of the crossed plants was plainly shown when
they were weighed,—cross to self-fertilized was as 100-37.
Hildebrand had similar results with a species of Corydalis-
He cross-fertilized sixty-three flowers. Of these sixty-eight
set fruit with 4.5 seeds per plant. He then self fertilized
sixteen flowers of these; only three set fruit. He then self-
fertilized twenty-seven flowers; none set fruit.
Behrens cites the following case: “Two tulips in separate
pots were brought into the house shortly before the flowers
opened. Gauze bags were tied over each of the flowers.
When full grown the gauze was removed. One was self-
fertilized and the other cross-fertilized. Both were again
covered with gauze and left undisturbed. The result was
that the cross-fertilized developed perfect fruit containing
seeds capable of germinating. The close fertilized produced
a stunted capsule with seeds incapable of germination.”
Change of Seed. It may be well to refer here to the
well-known belief that change of seed is advantageous.
There can be no question that small changes will be benefi-126
cial, but they may be also fraught with danger. The question
of climate must always be taken into consideration. Bailey 8,
who has given this question much attentions, says:	‘‘Even a
slight change, as between farms or neighboring villages,
sometimes produces marked results, such as more vigorous
plants and often more fruitful ones. We must not suppose,
however, that because a small change gives a good result, a
violent or very pronounced change, gives a better one.
There are many facts on record to show that great changes
often profoundly influence plants, and when such influence
results in lessened vigor or lessened productiveness we call it
an injurious one Now, this injurious influence may result
even when all the conditions in the new place are favorable
to the health and development of the plant; it is an influence
which is wholly independent, so far as we can see, of any
condition which interferes injuriously with the simple pro-
cesses of growth. Seeds of native physalis or husk-tomato,
were sent to me from Paraguay in 1889 by Thomas Morong,
then traveling in that country. I grew it both in the house
and out of doors, and for two generations was unable to
make it set fruit, even though the flowers were hand-
pollinated; yet the plants were healthy and grew vigorously.
The third generation grown out of doors set fruit freely.”
The husk-tomato experiment certainly shows that it is
not advantageous to have very great changes. The plant
must become accustomed to its new conditions before it will
succeed.
Bolley,Sa speaking of wheat seed, says: “Those who
grew the samples associated with like varieties of home-grown
seed have quite unanimously reported that there was no
marked difference in growth and development.”
8 Plant breeding.
8a North Dakota Agricultural Bxperimental Station, Bull. No. 17, p 86.127
“These tests and those recorded in Bulletin No. 1.3 are
indicative of the same conclusion, viz. That our best varieties
of wheat, as Blue Stem and Scotch Fife, are quite stable as
to the characters which they maintain and transmit to the
progeny under general methods of culture ” Across is good
because new combinations enter. If these are desirable and
strongly manifested, the plant is better fitted for the battle
of life.
Bailey says: “For the purposes of this discussion it is
enough to know that crossing within the variety and change
of stock within ordinary bounds are beneficial, that the re-
sults in the two cases seem to flow from essentially the same
causes, and that crossing and change of stock combined give
much better results than either one alone, and this benefit is
expressed more in increased yield and vigor than in novel
and striking variations.”
Darwin says on this point. “It is a common practice
with horticulturists to obtain seeds from another place having
a very different soil, so as to avoid raising plants for a long
succession of generations under the same conditions; but
with all the species which freely intercross by the aid of
insects or the wind, it would be an incomparably better plan
to. obtain seeds of the required variety, which had been raised
for some generations under as different conditions as possible,
and sow them in alternate rows with seeds matured in the old
garden. The two stocks would then intercross, with a
thorough blending of their whole organizations, and with no
loss of purity to the variety, and this would yield far more
favorable results than a mere change of seed.”
Impotency. John Scott10 observed that in a species of
Primula (Primula vertitilatla), although the stamens and
10 See Hildebrand, geschlechter vertheilung bel den pflanzen, p. 68.128
pistils are so arranged that self-pollination can take place
readily, seed did not set unless pollen was brought from
another plant.
Gaertner was unable to self-fertilize Lobelia fulgens,
although fertile seeds were produced when the pollen of
other species was used. The same state was found to exist
in Veibascum nigrum, and according to Tinzmann in the
potato (Salanum tuberosum).
Darwin,11 Fritz Mueller and others, made observations
to show that the pollen has no effect unless it comes from a
different plant. It has been shown that the pollen from
another flower of the same plant is scarcely more potent
than pollen from the same flower. Now, the greater differ-
ence in the individual, the greater the potency. In some
cases the potency is greater from a different variety. Fritz
Mueller has made the interesting observation that in some
plants when the pollen is placed on the stigma of the same
flower, it has no more effect than. dust. In other cases when
the pollen of the same flower was placed on the stigma, it
acted on it like poison. The flower faded and fell oft.
Flowers not so treated on the same branch remained fresh.
Darwin has shown that in plants known as heterostyled the
number of seed produced in illegitimate unions was small
indeed and full fertility only resulted when the pollen from
stamens was brought to styles of the same length.
It is well know that in Australia there was much difficul-
ty in getting clover to seed until the introduction of the
bumble bee. Experiments12 have been made in this country
as well as Europe to show that clover must be cross-pollin-
11	Different forms of flowers. Cross-feRtilization, p. 219.
12	Darwin, cross-fertilization, p.261, etc., etc.
Sirrine; Bull, 13, Iowa Agrl. Exp. Sta.129
ated in order that it may set seed. The following experi-
ment made by F. A. Sirrine on the college grounds, indicates
clearly that self-fertilization does not occur in red clover.
Two plants were covered with cheese cloth to prevent insects
from getting in. In one plant nothing was done to see if
self-pollination could take place. In the second case, which
was a white spur of red clover, artificial pollination was
effect with its own pollen. In neither case was seed obtained.
Whenever pollen from another variety was used seed set.
Many grasses are cross-fertilized. Hackel13 says:	“In
some hermaphrodite flowers, cross-fertilization is so much
the rule that they have lost the power of effectual selt-fertili-
zation, as in rye.”
Cucurbits. Some years ago the writer made some ex-
periments in crossing cucurbits. It was difficult to get
seed when pollen from the same vine was used. Frof.
Bailey had previously shown this to be true He says:
“The species are so exceedingly variable that all the hybrid
individuals may be unlike, so that there can be no crossing
between identical stock; and, if in-breeding is attempted, it
may be found that the flowers will not in-breed. And the
refusal to in-breed is all the more strange because the sexes
are separated in different flowers upon the same plant. In
other words, in my own experience, it is very difficult to get
good seeds from squashes which are fertilized by a flower
upon the same vine. The squashes may grow normally to
full maturity, but be entirely hollow, or contain only empty
seeds. In some instances the seeds may appear to be good,
but may refuse to grow under the best conditions. Finally,
a small number of flowers may give good seeds. I have
13 The true grasses. English translation, Scribner and Southworth, p. 18.130
many times observed this refusal of squashes (Cucurbita
maxima to in-breed.”
Pears:	Waite,13a in his well known experiments, has
shown that certain varieties of pear are self-impotent. His
conclusions are as follows:	“The results under those vary-
ing conditions have substantially agreed, in most cases being
remarkably uniform. The fruits resulting from the differnt
kinds of pollen showed interesting differences, which tend to
corroborate the conclusions.”
“It should also be noted that similar experiments were
tried on the apple and the quice along with the pear work.
The varieties of apples are more inclined to be sterile to their
own pollen than the pears. With the former in the great
majority of cases no fruit resulted from self-pollination ”
“(1) Many of the common varieties of pears require
cross-pollination, being partially or wholly incapable of
setting fruit when limited to their own pollen.”
“(2) Some varieties are capable of self-fertilization.”
“(3) Cross-pollination is not accomplished by applying
pollen from another tree of the same grafted variety, but is
secured by using pollen from a tree of a distinct horticul-
tural variety, i. e., which has grown from a distinct seed.
Pollen from another tree of another variety is no better than
from the same tree. This failure to fruit is due to the steril-
ity of the pollen and not to mechanical causes.”
“(4) The impotency of the pollen is not due to any
deficiency of its own, but to the lack of affinity between the
pollen and the ovules of the same variety.”
“(5) The pollen of two varieties may be absolutely self-
sterile and at the same time perfectly cross-fertile.”
13a The pollination of Pear Flowers. U. S. Dept. Agric., Div. of Veg.
Pathology, Bulletin No. 5, pp. 81-82.131
“(9) Pears produced by self-fertilization are very uni
form in shape. They differ with crosses not only in size and
shape, but also in some cases in time of maturity and in
flavor.”
“(11) Self-fecunded pears are deficient in seeds, usually
having only abortive seeds, while the crosses are well sup-
plied with sound seeds.”
These same facts may be extended to many other plants,
but space will not permit us to dwell on this at greater
length.
Superiority of Grossed Plants. Behrens says: “Cross-
fertilization produces the greatest number of seeds capable of
germinating, while self-fertilization tends to produce few or no
seeds capable of germinating. Self fertilized ovaries, on the
whole, produce fewer seeds than cross-fertilized. The seeds
produced by self-fertilization are on the average smaller and
lighter than those produced by cross-fertilization. The plants
from self-fertilized are on the average smaller and weaker
^than those from cross-fertilized.”
^ Hermann Mueller14 comes to essentially the same con-
clusion, and adds, “that the product of self-fertilized can
resist unfavorable conditions, such as sudden changes of
temperature, much better. The superiority of crossed plants
does not depend on the mere separation of the plants, but it
brings together the properties of two individuals which have
a slightly different constitution.” Gray16 says:	“It is seen
to be a part of the general ‘economy of nature,’ a phrase
which has a real meaning. One good illustration of it is
furnished by the pollen of flowers. The seeming waste in a
14	Die Wechselbeziehungen zwischen den blumen und den ihre kreuzung
vermittelden insekten.
15	Darwiuiana, p. 375.132
pine forest is enormous. It gives rise to the so-called
‘showers of sulphur’ which everyone has heard of.” Myriads
of the pollen grains are scattered by the winds to one which
reaches the stigma to fertilize the ovule. In close fertilized
flowers a small amount of pollen is produced. Now in the
contrasted case, that of pine trees, the vast superabundance
of pollen would be sheer waste if the intention was to fertilize
the seeds of the same tree..
' Wallace says.16 “The facts as to the cross-fertilization of
flowers which have been briefly summarized, taken in con-
nection with Darwin’s experiments proving the increased
vigor and fertility given by cross-fertilization, seem amply to
justify his aphorism, ‘Nature abhors self fertilization,’ and
his more precise statement, ‘No plant is perpetually self-
fertilized.' ”
' c „ ...	In the flowers considered so far the in-
Silf-Pollmation.
tent appears to be to secure cross
pollination, but there are many plants in which self-pollina-
tion is the rule. This is unknown in autogamy. Autogamy
cannot, of course occur in any other but perfect flowers.
In Adoxa moschatteliina the flowers are proterogynous.
When the stigmas are receptive the anthers are short; they
lengthen out and finally leave some of the pollen on the
stigma. If cross-pollination has not occurred, there are still
chances for self-pollination. In the early flowers of some
species of Geranium the five stigmas are receptive. The
anthers, of which there are ten, have not dehisced. In a day,
or less in some cases, the anthers discharge their pollen on
the stigmas. The flowers close at night, and the following
morning the five stamens next to the corolla lengthen,
straighten out and deposit their pollen on the stigmas.
16 Darwinism, see page 221.133
Hermann Mueller, in giving- a general retrospect on the
subject of cross-pollination, says in regard to self-pollination;
“Where cross fertilization that had once been insured be-
comes uncertain owing to the competition of other flowers,
(e g. Malva rotundifolia, species of Geranium), or owing to
the unfavorable locality (as Lysimachia nemorum) or unfavor-
able weather (as Veronica beccabunga), the mechanisms of the
flowers have in many cases undergone a change such as to
render self-fertilization again possible; in a few cases rever-
sion toanemophily has taken place (Artemisiaceae, Thalictrum).
As examples of the countless ways in which plants revert to
self-fertilization in default of sufficient insect-visits, I may
mention the following:	In some dichogamic flowers the
stigmas curl back upon the anthers or other parts which still
retain some pollen (Stellaria graminea, Malva rotundifolia,
species of Geranium, Compositae)) the stigmas sometimes curl
back till they come in the line of fall of the pollen (Melam-
pyrum pratense) or even place themselves between the anthers
(Rhinanthus minor)-, anthers which stand in a ring around the
stigma, may, in default of sufficient insect-visits, converge
above the stigma, applying their pollen to it (Myosotis,
Lithospermnm, Cruciferae); even mechanisms which eflect
cross-fertilization with astonishing precision in case of insect-
visits are not [infrequently transformed so as to render self-
fertilization inevitable when insect-visits are few (certain
Orchidaceae, Fumariaceae, Salvia); or the production of
cleistogamic, self-fertilized flowers may compensate for the
loss of the power of self-fertilization in the ordinary flowers
(Viola)."
Oleistogamous Flowers. The intent in these is cer-
tainly to have self-fertilization, and it is remarkable that the
closed flowers are very productive of seed, more so than many134
open flowers. Some of our violets and polygalas produce
two kinds of flowers. The early ones are irregular and
adapted to insect pollination. In the late flowers, which are
closed, the pollen has been reduced to a minimum.
In a large number of plants self-fertilization is the rule.
But many of these are occasionally self-fertilized so that the
rule is not invalidated. But there are plants which have
have special arrangements for securing self fertilization,
as in some buttercups (Ranunculus) sandwort (Spergula),
willow herb (hpilobium), but these may also be cross
fertilized occasionally. But there are cases in which there
are no chances for cross-fertilization. Such are plants which
produce cleistogamous or closed flowers. These, according
to Darwin17, occur in twenty-four natural orders. But
additions are constantly made, and Hemsley believes that
they occur in nearly all the natural orders. In many plants
which produce these closed flow'ers, irregular insect pollin-
ated flowers are produced. These closed flowers produce a
minimum of pollen, but an abundance of seed; much more
so than do the flowers of the same plant pollinated by insects
and therefore possibly cross-fertilized, some of our violets
Viola palmata var. cucullata) often have these cleisto-
gamous flowers, and although my observations are not
crucial, I have seen the seeds in their pods much more
abundant than in the irregular flowers produced early in the
season. This is certainly the case in the dog violet ( Viola
canina)• All of the plants that produce cleistogamous
flowers also have those of other kinds; not always in the
same locality, as in a small rush (Juncus bufonius)- In
some places this plant produces closed only, while in other
parts perfect flowers are produced.
17 Different forms of flowers.135
Autogamy and Alpine Plants■ Loew. in his “Bine-
ten biologische Flotistik,’’ has collected statistics of the obser-
vations made upon flowers with reference to insect visitors and
autogamy, from which it appears that self-fertilized plants
are more numerous among alpine species than among those
of a lower level. Observations are not at hand to indicate
whether the same state of affairs exist in this country, but I
am inclined to doubt that this is true for Rocky Mountain
species. Kerner accounts for autogamous flowers in these
regions because of the shortness of the season and the broken
condition of the weather. While the climate above timber
line in the Rocky Mountains is rigorous and at times un-
favorable, the mornings are usually bright and sunny. A
few hours spent in collecting the insect fauna on such alpine
plants as Mertemia, Primula, Omphalodes, Silene,
Actinella, Trifolium and Astragalus leaves some doubt
in my mind in regard to autogamy.
Autogamy in Grasses Hackel says in regard to
barley: “ Cross-fertilization is much more rare and difficult
in barley, and in certain races like the six:ranked, the short-
spiked, two ranked and the peacock barley. The flowers,
especially in our climate, never open and consequently cross-
fertilization is made impossible.”
Two of our native grasses (Leersia oryzoides and Am-
phicarpum Purshii) produce cliestogamous as well as the
ordinary flowers. The closed flowers are abundantly fertile,
while the others are not. Meehan says:18 “All plants that
are arranged for self-pollination are abundantly fertile and
have a great advantage of numbers in the struggle for life.
18 Proceedings Academy of Natural Sciences, Aug. 26,1890. See p. 271. Also
May 26, 1890, Proceedings American Association for the Advancement of
Science, Detroit meeting, etc.136
While those that have to depend on external agencies are
usually less productive, and even though the progeny may
be found to have greater vegetative vigor, or some other
element of strength.
Mr. Henslow says: “Thus orders of plants with easy
access to the honey are some of the most abundant, as
Ranunculaceae, Compositae and Umbelliferae, as well
well as are those dependent upon the wind which never fails,
such as willows, Cyperacae, and grasses. On the other
hand all regularly self-fertilizing plants are abundant, and,
together with certain wind-fertilizing plants, are cosmo-
politan. ”
Cause for Cleistogamy■ Kerner makes the follow-
ing suggestion in regard to the conditions affecting cleistog-
amous flowers:	“No open, aerial flowers were produced
by Viola sepincola so long as it grew in the cool shade
of a dense wood, but when transferred to open ground,
accessible to sunlight, such flowers were developed. One
can hardly err in ascribing to the sun’s rays a very import-
ant influence in stimulating plants to the inception of flower
ing shoots, especially such as bear blossoms possessing
bright-colored petals. Indirectly, however, this advantage
accrues to the plants in question, that, living as they do in
the deep shade, where no bees would, in any case, visit them
if they had open flowers, they can confine their constructive
energy to the inception and development of cliestogamous
flowers and save themselves the trouble of producing open
flowers adapted to cross-pollination (but useless in the place
in question). If the spot where the violet grows becomes
exposed to the sunlight thiough the trees shading it being
blown down or felled, bumble and hive bees make their
appearance in search of honey, and buzzing from flower to137
flower, crosses one with another.” Climate is no doubt an
important factor.
Now, everyone knows how vigorous are plants like
knot-weed, horse-weed, buttercups, thistle, plantains, etc.
They are world wide and it is equally true that they are self-
fei'filized. Wallace says: “That self-fertilization has some
great advantages is shown by the fact that it is usually the
species which have the smallest and least conspicuous flowers
which have spread widely, while the large and showy
flowered species of the same genera or families, which re-
quire insects to fertilize them have a much more limited dis-
tribution.”
It must be admitted that inter-crossing is not necessarily
good, but also that close inter-breeding is not necessarily
bad. Says Wallace: “The rabbits on the Island of Porto
Santo have originated from a single female. They have
lived there for 170 years and are still vigorous.” But close
inter breeding does produce bad results, especially if care in
selection is not used. The inter breeding is not injurious if
there is a change of conditions and proper selection.
Wallace concludes:	“From a consideration of these
varied facts we conclude that an occasional disturbance of
the organic equilibrium is what is essential to keep up the
vigor and fertility of any organism, and that this disturb-
ance may be equally well produced, either by a cross between
individuals of somewThat different constitutions, or by occa-
sional slight changes in the condition of life.” In plants of
wide dispersion there is a constant change of conditions;
these can exist for a long time without inter-crossing, but
in plants not so widely distributed a cross is needed to
keep up the fertility. Why the production of an enormous
quantity of pollen in case of the pine and other wind138
pollinated flowers if self-fertilization is more advantageous?
Pollen is rich in nitrogen, and this is a costly element. Why
the exquisite adaptations in orchids and other flowers if self-
fertilization is preferable ? We are justified in concluding
that cross fertilization is advantageous.CHAPTER VIII.
THE EFFECTS OF CBOSS-FERTILIZATION IN PLANTS.
There has been much discussion, both popular and
scientific, on the question of the effects of cross-fertilization
in plants. It is conceded by all authorities that there is an
effect, the point at issue is mainly whether it is immediate or
manifests itself later. Most authorities now agree that it is
immediate in some cases at least. It is well known that in
some cases pollen has an immediate influence on the fruit or
seed. This has long been known to be the case in corn. As
long ago as 18581 2 it was observed that when differently
colored varieties grew near each other they affected each
other’s seed. Later experiments were tried by Dr. Savi and
Hildebrand. Both have come to the same conclusion.
P. Dudley3 writes as follows:	“Indian corn is of several
colors, as blue, white, red and yellow. If these sorts are
planted by themselves, so that no other be near them they
will produce their own color; but if you plant the blue corn
in one row of hills as we term them, aud the white or yellow
in the next row, they will mix and interchange color.” Dr.
Sturtevant3 says: “ Corn, the maize plant, shows in its
kernels the influence of cross-fertilization of the same year.
Some varieties seem to possess the power of resisting either
1	Darwin: Animals and plants under domestication, Yol. I, p. 430.
2	Philosophical Transactions Abridgement, Vol. VI, Pt. II, p. 204-205.
Kellerman and Swingle, Second Annual Rep. Kansas Agrl.Exp. Station, 1889,p. 345
3	Second Annual Rep. New York Agrl. Exp. Station p. 37-56,1	Leaves of New Prolific Marrow, (Cucurbita maxima).
2	Cucurbita pepo to the right vegetable marrow, to the left the product of
a cross between vegetable marrow and long warted.141
3	C. maxima, from seed grown in with c. pepo mixed with prolific marrow.
4	Variations of perfect gem (C. pepo), the type shown to the left; in color
all were perfect gem, but in form variable, showing effect of pumpkin, long
warted, &c.
5. Common pumpkin (C. pepo) on nest-egg gourd, C. pepo; all photographed
by F. A. Sirrine.142
cross-fertilization or the changes induced thereby. Crozier *
writes (Cross between StowelPs Evergreen and Yellow Hath-
away): “These observations show that foreign pollen effects
the appearance of the crossed kernels the first season, but
also that an unusual appearance may be due to a cross of the
pievious year. Prof. Beal4 5 says: “During the year past I
planted near each other three hills of the following kinds of
corn, well mixed together, viz.: Waukashum, White Flint,
Black Pop Corn, Early Minnesota Sweet, King Phillip and
Black Sugar. Every ear showed a mixture produced by
pollen from one or more of the varieties except those of the
King Phillip variety.”
But flint corn6 did not show the effect of pollen from
dent corn in the first year. Kellerman and Swingle7 who
crossed a large number of varieties have come to the same
conclusion that other observers have; namely, that the so-
called varieties of maize cross more or less freely, and the
effects may or may not be visible the first year. As a result
of some work done on the college grounds Professors Crozier
and Rolfs8 write concerning the immediate influence of cross-
fertilization upon the fruit: “In all cases some, and in some
cases all of the ears changed in appearance in the direction
of the variety furnishing the pollen.” A practical gardener,
Mr. F. S. White,9 writes as follows: “The past season I had
sixteen varieties of white sweet corn, and also a small lot of
Black Mexican. When I came to save my seed corn I found
grains of this black corn stuck in every variety.”
4	Proceeding’s Soc. Prom. Agrl. Science 1887, p. 1.
5	Report State Board of Agriculture, Michigan, 1879, p. 198.
6	Beal: Report State Board of Agriculture, Michigan, 1878, p. 450.
7	Second Annual Report Kas. Agrl. Exp. Station, 1889, p. 288. Seealse First
Annual Report, p. 316.
8	Agricultural Science, Vol. IV. p. 23.
9	Iowa State Register, December 11,1891.143
In 1896 a neighbor planted some popcorn in close
proximity to sweet corn. In every case there was an imme-
diate effect. Oases of this kind are numerous.
I have given enough evidence to show the immediate in-
fluence of pollen on corn. It is only necessary to add that in
some cases it would seem that the varieties of corn are not
sufficiently fixed, and that a change from the type may be
due to a previous cross.
The opinions in regard to other plants are very diverse.
Crozier10 says. ‘‘The writer is disposed to think that the
evidence is still insufficient to show that there is an observ-
able effect of cross upon the ovary the first year except in
Indian corn.”
Darwin observes that when white and blue varieties of
the pea are planted near each other, they mutually cross, and
in the autumn, blue and white peas were found in the
same pod. There has been much discussion concerning the
immediate effects of the pollen of certain varieties of the
orange. Budd assures me he has made personal observa-
tions in California, and thinks there can be no question as to
its immediate efiects. Darwin cites a case in which Gallesio* 11
fertilized the flowers of an orange with pollen from the lemon;
and one fruit thus produced bore a longitudinal stripe of
peel having the color and flavor of a lemon.
California orange-growers are convinced that the naval
orange shows itself where this pollen is used. In several
hybrid plums and grapes that I have seen, no immediate
effects was visible, although there is said to be an immediate
effect in some pears, and Waite found this notably true in his
experiments.
10	Department of Agriculture Report, 1887, p. 213.
11	Darwin; animals and plants, etc,, p. 430.144
In regard to the apple there is some difference of opinion.
There are many who believe the action is immediate. Crozier
and Rolfs in experiments made a few years ago on the col-
lege grounds found no difference when the Oldenburg apple
was crossed, although the pollen was obtained from ten
different varieties, using it as a female plant. The fruits
were all alike and resembled uncrossed specimens of the
Oldenburg. The Iowa State Horticultural Society has at its
trial stations done much crossing and hybridizing. Numerous
varieties were crossed on the Soulard and other forms of the
wild crab (Pyrus coronariu). Oollman, Fluke and Watrous
all inform me that they could see no immediate effect of the
pollen on ihe wild crab. It was in all essentials a wild crab.
Darwin, however, gives evidences to show that the effect
may be immediate in some cases. In another case a smooth
apple affected a rough coated kind. The remarkable St.
Vallery apple, in which the stamens are abortive and do not
produce pollen, is of interest in this connection.
When artificially pollinated the fruit differs in size, flavor
and color, but resembling in character the perfect kinds with
which they have been fertilized. This case may not be so
strong as started by Darwin. Crozier, who looked up the
original French reference, think there is some doubt in regard
to it. I have several times had my attention called to apples
which plainly showed two varieties; in one case an apple
was half Baldwin, the other half was a greening. Some
years ago I saw some apples, one-half of which were gros
poinier, the other half was unknown to me. It was thought
that these showed an immediate effect, but I was unable to
get a further history of the case.
It is a very common belief that there is an immediate
effect in the crossing of cucurbits. Such is, however, not145
the case. Prof. Bailey, who lias made more than a thousand
careful hand pollinations and has obtained more than a
thousand types of pumpkins and squashes, has never seen
any immediate influence, except such as was due to imperfect
development, caused by insufficient or impotent pollen.
Several years ago, in conjunction with Mr F. C. Stewart,
some experiments were made in crossing cucurbits. Many
careful hand pollinations were made, but in not a single case
was any immediate effect observed. When this seed was
planted the following year hundreds of new forms made
their appearance. We are justified in concluding that there
is no immediate effect.
Charles Darwin: Animals and plants under domestication. Vol I, p. 430.
P. Dudley: Philosophical Transactions Abridgement, Vol. VI, Pt. II., p.
304-205.
Kellerman and Swingle, Second Annual Rep. Kansas Exp. Sta., 1889. p. 346.
Lewis Sturtevant: Second Annual Rep. New York Agrl. Exp. Sta, p. 37-56.
A. A. Crozier: Proceedings Soc Prom Agrl. Science 1887, p. 1.
W. J. Heal: Report State Board of Agriculture, Michigan, 1879, p. 198.
Beal: Report State Board of Agriculture, Michigan, 18<8, p. 450.
Kellerman and Swingle: Second Annual R.epnrt, Kas^A^r!. Exp. Station,
1889, p.288. See also First A unuaT Report, p. 316.	"	_____
Crozier and Rolfs: Agricultural Science, Vol. IV, p. 23.
F. S. White: Iowa State Register, December 11, 1891.
A, A. Crozier: Department of Agriculture Report, 1887, p. 312.
Focke: Pflanzenmischlinge. p 475.
P. H. Pammel: On the Crossiug of Cucurbits, bulletin No. 19, Iowa Agricul-
tural Experiment Station, pp. 595-600, November, 1892.
The Crossing of Cucurbits, proceedings of the sixth annual convention of
the Association of Agricultural Colleges and Experiment Stations, New Orleans
meeting, November 15-19, 1893, pp. 94-97.
On the Crossing of Cucurbits, transactions Iowa Horticultural Society, 1892,
volume xxvii, pp, 327-332.
Brandza, Rev. Gen de Bot. 1890, pp. 301-305. Bot. Centralblatt, XLV1, p. 124
and p. 40. Hildebrand, Bot. Centralblatt Vol. XL, p. 46.
Macfarland: Botanical Gazette Vol. PVI, p. 255. A Comparison of the
Minute Structure of Plant Hybrids with that of our Parents and its bearings
on Biological Problems. Transactions of the Roy. Soc, Edinburgh XXXVII, pp.
203-208. Bot. Centralblatt LIII, p. 379.
L. P. Pammel: Cross Breeding of Plants and Hereditary, Rural Life, Oct.
19, 1893. p. 12.
Vilmarrin: Pedigree or Grade Races in Horticulture, Gardner’s Chronicle
Vol. XIV, 3d series p. 301, p. 332. See p. 332.CHAPTER IX.
HYBRIDS.
Camerarious, in 1694, thought, on certain grounds, that
hybrids could occur, and Gmelin found a new Delphinium
in his garden which he concluded was a hybrid. Linnaeus
appears to have been successful in the production of a hybrid
between Tragopogon pratensis and T. porrifolius; this flowered
in 1759, though as early as 1719 Thomas Fairchild produced
a hybrid of Dianthus Caryophyllus and D. barbatus.
As early as 1791 Koelreuter produced a large number of
hybrids. These early experiments in hybridization gave un-
doubted proof to those who doubted it, of the sexuality of
plants. Koelreuter produced his first hybrid between Nicot-
iana rustica and N. paniculala. Thomas Andrew Knight,
during the latter part of the Eighteenth Century, did a great
deal of work in hybridization.
Of the later workers, from 1826 to 1880, mention should
be made of Gaertner, Herbert, Naudin, Gadron, Focke and
a host of modern workers.
The term cross is used to designate the offspring from
the union of two different plants of the same species or
variety, the union of the variety being more violent than that
of the same species. The hybrid is the result of the union
between two species, as blackberry and raspberry. It is
difficult in some cases to say what constitutes a species, as
botanists do not always agree as to its limits. In some few
cases hybrids have been produced between two distinct147
genera, as in the case of wheat and rye hybrids, or those of
Brassica and Baphanus, also in Lychnis and Silene\ Aegilops
and Triticum. They are not uncommon in certain orders, as
in the pink, cactus and orchid families.
In a state of nature hybrids are not common. A full
list up to 1881, is given by Focke. They are most
numerous in willows, oaks and verbenas Prof. Bailey who
has given Carex much attention, states that out of one hun-
dred and eighty species in the Northeastern States, only
eleven hybrids are recorded. When we come to cultivate
plants, Prof. Bailey says:	“Hybrids have been produced
between the raspberry and blackberry by two or three per-
sons, but they possess uo promise of economic results.
Among the list of garden vegetables (plants which are propa-
gated by seeds) I do not know of a single important hybrid.”
“It is true that there are many grape hybrids like the
Agawam, Lindley, Wilder and Brilliant, and of pears like
the Kieffer. In ornamental plants hybrids are numerous and
in many of these they are carefully cultivated and nursed
If these plants are left to shift for themselves, they soon lose
their charm.”
Focke concluded that the parental
Parental Characters. ,	,	,	. .
characters may be variously inter-
mingled; (l)a mean between both parents is maintained in
all parts of the plant, (2) the characteristics of the father or
mother predominate, (3) certain parts of the hybrid exhibit
the maternal and others the paternal characters.
Weismann, in speaking of the control of parental char-
acters, says:	“In any inquiry with regard to the factors
which control the struggle of the parental characters, it must,
above all, be borne in mind that the cells are always the
determining agents. The determinants of the father and148
mother come together in the cell, and in the cell only; and
all characters, whether relating to a large part of the organ-
ism, or merely to a single cell, can only be determined by
processes taking place within the substance of one or of
many cells ”
Kerner says:	“Some of their attributes and external char-
acters are derived from the paternal, some from the maternal
stock. If the relative admixture of the two stocks were to be
determined in the case of the hybrid by summing up the
characteristics transmitted from each source, the share of
each parent would, in many cases be found to be half. In
such a case it is usual to say that the hybrid is a mean be-
tween its parents. Examples are afforded by Geum hybridum,
which originates from crossing Geum montanum and G.
rivals,."1
Hybrids are changed with reference to the production of
seed, so much so that hybrids seldom if ever produce seed,
and therefore do not propogate sexually. They show a
marked change with reference to variability. In closely
related species they flower earlier and longer with usually a
luxuriant growth.
Focke states that he is of the opinion that genera with
zygomorphic flowers, belonging to orders with actinomorphic
flowers, show especial prediliction for hybridization. Pelar-
gonium of Geraniaceae and Nicotiana of Solanaceae. It appears
to be difficult to hybridize plants growing in different
situations.
• “As a general thing, when species are closely related
hybrids are more easily produced, as in many Solanaceae,
Caryophyllaceae, Iridaceae Salicaceae. In other orders it is
difficult to obtain hybrids, as in Coniferae and Leguminosae.
Species of Vitis, Salix and Dianthus hybridize readily, but149
Si'ene with difficulty; Nicotiana, Verba scum and Geurn easily,
but Solannm, Linaria and Potentilla with difficulty. Some-
times hybridization will not occur in closely related species,
as the apple (Pyrus malus) and pear (P. communis).
Kroelreuter observed in his hybrids that in part they
partook more of the mother than of the father, or the re-
verse. In some cases where one parent had yellow flowers
and the other red, the hybrid had variegated flowers. When
a hybrid was produced between an early fllowering and a
late-flowering plant, the hybrid was between the two in time
of flowering.
Hybrids of species of closer relationship, or the crosses
are usually strong and productive. Such plants are char-
acterized by their greater size, rapid growth, early matura-
tion of the flowers, longer life, greater productiveness and
unusual size of the separate organs. In hybrids produced
from Rhododendron arboreum and Catawbiense the flow-
ers mature earlier. In some species of Rhododendron and
many other plants hybrids are sterile. Hybrid seedlings of
Nymphcea alba are difficult to grow.
Hybrids of Salix viminalis and S■ purpurea are
said to be much more sensitive to frost than the species. On
the other hand crosses of Nicotiana suaveolens and N
tabacum-lattissimum resist frost better than the species.
Focke adds, “That hybrids of different species contain
less pollen in their anthers than those of the mother plant,
and the fruit contains a smaller number of seeds. Frequently
they contain neither pollen nor seed.” It is also a well-
established fact that the closer the relationship between
species the easier it will be to obtain fertile hybiids.
Sachs says: “The characteristics of the parent-forms
are as a rule so transmitted to the hybrid that the influence150
of both is manifested in all its characters, producing a
fusion of the different peculiarities. This is more evident in
the species than in the variety hybrids; in the latter some of
non-essential characters of the parent sometimes present
themselves in the offspring uncombined side by side; e. Q.,
various kinds of streaks and blotches instead of a mixing of
the colors of the flowers. Thus a hybrid which Sagaret
obtained from Cucumis Chate (female) with C- Melo
Cantalupus (which had a reticulated flesh) had a yellow
flesh, a reticulated marking of the rind and moderately
prominent ribs like the male parent, but white seeds and an
acid flavor like the female parent. Another hybrid from
the same species had, on the contrary, the sweet flavor and
yellow flesh of the male, with the white seed* and smooth
rind of the female parent.
As a rule, hybrids may be produced reciprocally, but
sometimes this does not occur. Thus Koelreuter found that
when the pollen of Mirabilis longiflora was applied to
M. Jalapa, a hybrid was produced, but the reverse ex-
periment failed.
An extraordinary number of rose hybrids have
Rose Hybrids.	1 t* ■ ■ -j
been produced. It is said that on the average
sixty new rose hybrids come on the market every year.
The statement has been made that more than 6,400 roses
have been produced up to the present time by crossing and
hybridization.
Quite a large number of hybrids have been produced at
the Iowa Agricultural College between Rosa ruffosa, Rosa
Arkansana and cultivated roses.
Rosa rugosa and General Jacqueminot■ They pre-
sent some remarkable variations. In color of flower, leaf
and seed the hybrids indicate weaker germinating capacity.151
J. L. Budd and N. E. Hansen state that “The tallest hybrids
showed the most marked modification in foliage. One hun-
dred and thirty-two of the plants showed marked variations,
many of them showing no rugosity of leaf, while others are
intermediate in foliage. Those following most nearly crenate,
while those of the hybrids showing no rugosity of leaf are
serrate. The rugosa leaflets vary in number from five to
nine, the usual number being seven, and a few of the points
of growth only five.- In some of the hybrids the usual
number is five, with an occasional leaf bearing seven, and
the leaflets average larger in size, Several of the hybrids
have very small leaflets, and are dwarf in habit.”
The Rosa rugosa evidently exerted a prepotent in-
fluence and this has also been observed in other hybrid
roses, where the rugosa ovules were fertilized with other
pollen. The rugosity of the leaf is certainly marked in
many cases.
We have on the college grounds a hybrid between
the Oldenburg apple (P Malus) and P. Tor ring o,
in which the character of leaf and flower are somewhat in-
termediate. The flowers of the hybrid are very much
smaller than those of the Oldenburg, but larger than those
of Torringo. The leaves are larger than those of Torringo,
but not so large as those of the Oldenburg. The fruit is
somewhat larger than that of P. Toringo with the peculiar
blush of the Oldenburg.
Miss Sirrine, who made a mscroscopical examination of
the hybrid and the parents, found that the offspring had
many of the internal character of the parents, which sub-
stantiates the work of Macfarlane and others.
Another interesting hybrid is the Soulard crab. This
was at first supposed to be a good species, but it has the152
undoubted characters of P. Malus. However, it shows
that P. cortmaria had a strongly prepotent influence upon it.
Do squashes and pumpkins mix with watermelons ?
Curbits. ^ g YVhite says:	“This is a question that
has been a puzzle to many, because we never see a pumpkin
seed in a melon, nor is there any change in the melons, or
apparant mixture in the seed. Yet I am sure that melons
grown near pumpkins will get so mixed with the pumpkins
as to be untit for use.” Now this is a general belief among
gardeners, and my friend Mr. White states the case from
his observations, but I desire to correct an error due to a misun-
derstanding of the limits of species. What is commonly called
a squash is a pumpkin, Cucurbita Pepo, and not squash,
C. maxima■ Equally general is the belief that cucumbers
spoil muskmelons. Prof. Bailey has shown that, it is ex-
tremely doubtful. Ninety-seven muskmelons of many varie
ties were pollinated with cucumber pollen of many kinds.
No fruit set. Twenty-five cucumber flowers were pollinated
with muskmelon pollen; only one fruit developed, but that
was seedless. In our own experiments in no case was there
any evidence of “mixing” between the squash and pumpkins
and melon and pumpkins. The off flavor in melons is due
to reversion.
Parkman has recorded some interesting observations
on the hybrids between two Japanese lilies, L. speciosum
and L. auratum. The pollen of L auratum was applied to
the stigma of L. speciosum and the result was that some good
seed was produced. It appears that in the fifty young plants
produced the stems were mottled like L. auratum, showing
the influence of the male parent. The flowers of the first
were like those of L. speciosum but having the fragrance of
L. auratum. Now, of the other hybrids, not a single one153
was distinguishable from pure L. specie sum. As stated before,
the markings of the stem were those of L. auiatum, con-
sequently there was no doubt of their hybrid origin.
It is interesting to note here the variability or the differ-
ence in the influence of the male parent. This same fact has
been observed in many other hybrids where there are many
seeds in a vessel, and has also been observed in plants like
the thistle with many achenes in one head.
Sachs says: “When two species, A and B hybridize,
and the one species A exercises a greater influence on the
form and properties of the hybrid than the other species B,
the hybrid or its descendants, if fertilized by A, will revert
more quickly to the parent form A than it will to the parent
form B if fertilized by it Thus Gaertner states that the
hybrid of Dianthus Chinensis and D. Caryophyllus reverts to
the latter form after three or four generations if repeatedly
fertilized by it, while it requires fertilization for five or six
generations by D. Chinensis in order to revert to that form.”
A ternary hybrid is ODe which in-
Temary Hybrids. ,jjrectjy js the offspring of
three different species in this way, the hybrid
off spring of two species is united with the pollen
of a third species, as, for instance, the hybrids of Linaria
genistifolia and L. purpurea is fertilized with the pollen of L.
striata. The result is a ternary hybrid. Some of these
hybrids are not uncommon, for instance it is said that
Wichura produced a compound hybrid in which six different
willows entered.
Prepotency. It has been shown by numerous observeers
that when two races are crossed or the product a hybrid be-
tween two distinct species the result is a blending of the
characters of both. It has even been asserted by some in-154
vestigators that this character is shown in the make up of
the cell-tissues. Macfarlane in an interesting address before
the American Association of the Advancement of Science
m Washington has shown that some hybirds are exactly in-
termediate in histological character between parents, and
that normally there is an equal blending of both parents.
We have had under observation in interesting hybird be-
tween DeSoto plum (Prunus Americana) and an Oregon
plum (Prunus domestica?) In habit of tree and foliage
the hybirds assume the character of Prunus americana
our wild plum. This variety is strongly prepotent in trans-
mitting tendency to take a disease (Gladosporium carpop-
hylum) which does not occur on our cultivated European
plum (Prunus domestica). But this is by no means the
invariable rule. Darwin says. “It would appear that in
certain families some ancestor, and after him others in the
same family have had great power in transmitting their like-
ness through the male line.” Henry L. LeVilmora says:
“In framing the character of the progeny the action of
each parent is often very unequal, according to the power of
each in transmitting its characters. The one that is better
endowed in that respect stamps its features more firmly on
the cross-bred plant. Discussions have arisen on the influ-
ence of the male and of the female progenitor on a cross.
I believe that the strongest organism of the two, the one
rather which is best endowed with the power to transmit its
characters will predominate in the progeny, whether it
comes from the male or female parent.”
Graft There has been considerable discussion on the qnes-
Hybrids. tion 0f graft hybrids. Gardeners and horticul-
turists have maintained that hybrids have often been pro-
duced by budding and grafting. One of these has become155
well known from the researches of Charles Darwin, a common
laburnum. We will let Darwin describe the case:	“To
behold mingled on the same tree tufts of dingy-red, bright
yellow, and purple flowers, borne on branches having widely
different leaves and manner of growth, is a surprising sight.
The same raceme sometimes bears two kinds of flowers, and
I have seen a single flower exactly divided into halves, one
side being bright yellow and the other purple, so that one-
half of the standard petal was yellow and of larger size, and
and the other half purple and smaller. In another flower the
whole corolla was bright yellow but exactly half of the calyx
was purple. In another one of the dingy-red wing petals
had a narrow, bright yellow stripe on it; and lastly, in
another flower, one of the stamens, which had become
slightly foliaceous, was half yellow aud half purple; so that
the tendency to segregation of character of reversion affects
even single parts and organs. The most remarkable fact
about this tree is that in its intermediate state, even when
growing near both parent species, it is quite sterile; but when
the flowers became pure yellow or purple they yield seed. I
believe that the pods from the yellow flowers yield a full
complement of seed; they certainly yield a larger number.’'
“On the other hand, we have a clear and distinct
account given to Poiteau by M. Adam, who raised the plant,
showing that C. Adami is not an ordinary hybrid; but is what
may be called a grafted hybrid, that is, one produced from
the united cellular tissue of two distinct species. M. Adam
inserted in the usual manner a shield of the bark of C. pur-
pureus into a stock of C. laburnum; and the bud lay dormant,
as often happens, for a year; the sheld then produced many
buds and shoots, one of which grew more upright and
vigorous with larger leaves than the sh oots of C. purpureus
and was consequently propagated.”156
“If we admit as true M. Adam’s account, we must admit
the extraordinary fact that two distinct species can unite by
their cellular tissue, and subsequently produce a plant bear-
ing leaves and sterile flowers intermediate in character be-
tween the scion and the stock, and producing buds liable to
reversion; in short, resembling in every important respect a
hybrid formed in the ordinary way by seminal production.”
It may be interesting to mention here that Macfarlane
has examined the anatomical details of the tissue of this
alleged grafted hybrid and it shows a remarkable mingling
of the two parent forms.
In addition to this there is the famous Bizzario orange,
which is said to offer a strictly parallel case. It is said that
the tree produces at the same time leaves, flowers and fruit
identical with the bitter orange and the citron of Florence;
also fruit with the two kinds blended together both externally
and internally.
It is said when the variegated Jessamine is budded with
the common kind, the stock sometimes produces buds bear-
ing variegated leaves.
We may mention here the instance of the Jerusalem
artichoke (Helianthus tuberosus) which was grafted on the
common sunflower (H. ar nuus). It was stated that the sun-
flower had acquired from the artichoke the habit of producing
tubers. Yoechting has lately repeated this experiment, but
failed to get results anything like those recorded above for
the sunflower.
On the whole, I think it may be questioned whether
there is such a thing as a genuine grafted hybrid; it is best
to suspend judgment until these are produced by actual
experiment. Most of these statements rest upon the stories
related by gardeners, and these are not always trustworthy.Water Hemlock (Cicuta maculata L.) with flowers in masses