A ' DEPOSITORY Issnrd May 20, U. S. DEP \RTMENT OF AGRICULTURE, BUREA1 OF PLANT [NDUSTRY -Circular No. 26. B. T. GA1 l.<>\\ \V i SOME FACTORS AFFECTING THE KEEPING QUALITIES OF AMERICAN LEMONS. RODNEY II. TRUE, Physiologist i\ Ch w.< h . \N!) ARTHUR V. SIEVERS, Expert, Drug-Plant Investigations. h . office : [Cir. 26] 2 BUREAU OF PLANT INDUSTRY. Chief of Bureau, Beverly T. Galloway. Assistant Chief of Hunan. Albert V. Woods. Editor, J. E. Rockwell. Chief Clerk, James E. Jones. B. P. I.- I 16 SOME FACTORS VFFECTING THE KEEPING QUAL- ITIES OF AMERICAN LEMONS. SCOPE OF THE INVESTIGATION OF THE KEEPING QUALITIES OF LEMONS. There is ;i prevailing impression among fruit handlers that Ameri- can-grown lemons while possessing many points of superior attract- iveness arc open to the objection that they arc not long keepers. Assuming the correctness of this report, the source of this weakness demands a careful study of the whole lemon situation. The object of this investigation has been to gel a clearer understanding of the processes through which lemons are put after picking, with special reference to the bearing of these processes on the behavior of the fruit in the packing houses, during transit, and after it has reached the market. This broadly outlined study has for its practical object the determination of conditions affecting the keeping qualities of the fruit after it has reached the market. The hope is also present that through the results obtained improvements in some of the processes in\ esl igated ma\ be suggested. It has been made clear by the work thus far accomplished that the keeping quality of American lemons i- influenced by many factors, some acting on the orchard, some in the packing house, some in the car- during transit, and some at points far distant from California, thai is, in the market-. LOSSES OF LEMONS FROM PARASITIC DISEASES. Important among the factor- causing the loss of lemons arc para- sitic diseases derived from the orchard. These operate not only there but, unless infected fruit i- detected and discarded, also in the pack- \ series of physiological studies has been made in the Office of Drug-Plant investigations by the writer'- of tliis paper to determine the relation between the present methods of bringing lemons into condition fur the market and the keeping qualities shown by the fruit after shipment. These results are based on limited data, are advanced tentatively, and are subject to modification should further investigation require it. A strong demand for a report upon the results ilms far obtained, coupled with the fact that they are likely to be of some Bervice, seems to .justify their publication. — B. T, Galloway, Physiologist and Pathologist, "Sweated fruit' 1 is picked green when the proper diameter i- reached, and colored rapidly by storage in moist, tight, sweat or sweating ten!- in which a high temperature i- maintained, usually l>v mean- of oil toves burning in (lie room with the lemons or in a celler like room below the fruit and separated from the storage room by slatted floors. The humidity and heat, and perhaps carbon dioxid and other gaseous product- of combustion, acting to- gether bring about a rapid coloration of the fruit. Sweating is u-u- allv resorted to only when the price of lemon- is high and a rapid marketing of the crop is desired. It is generally agreed among lemon growers that sweated lemon- are less likely to keep than those colored gradually at lower temperatures. Since the condition- main- tained in -weal room- are highly unnatural and the result i- obtained in a most unnatural way. some attention has been given to the physio- logical factors involved in sweating. By far the larger part of the lemon crop is picked when the desired diameter of the fruit is reached, and this is colored up by "curing" at low temperatures in the packing houses. In some place- where the water loss from the fruit is likely to he relatively easy to control, an open floor covered by a roof i- sufficienl for a permanent storage structure. In order to enable the manager to modify condi- tion to suit the needs of the individual lot-, the lemon-, in boxes or trays, arc piled up in carload lot-, and each pile is covered by a heavy Canvas tent, id' which the sides and end- may he raised or lowered at" will. In those regions where water loss is less readily controlled, the storing house i- hoarded up with the usual wall- and end-. To secure uniformity of condition- with even greater ease, some growers have made use of cellar- under the houses. Lemons colored by this -low "curing" process may remain in the tent- or cellar a- long as six month- or more if market condition- require it. hut usually fruit i- marketed much sooner. In grading and packing the fruit for market some lemon houses handle the -wealed and tent-cured -oil- separately, hut this i- not the invariable rule. I i-ir. _>;] 6 FACTORS AFFECTING THE KEEPING i.U'ALITIES OF LEMONS. PHYSICAL CHARACTERISTICS OF THE DIFFERENT TYPES OF LEMONS. Lemons are known to be a most variable fruit in their physical characteristics. Not only is this true of trees of any given variety, but in some cases it is also true of the different fruits taken from the individual tree. The manner of handling water and fertilizers is commonly believed to be of great importance in getting smooth, well- shaped lemons. The lemon varies in general from a barrel shape to an almost spherical form marked by more or less pronounced pro- tuberant end-. Thick and conspicuous ends detract from the value of the fruit. The best size of lemon weighs on the average 120 to 135 grains. Of course size is not the only factor which determines the weight, much depending on the rind, quantity of juice, and gen- eral solidity of the fruit. The most desirable sizes of lemons average 300 and 360 to the box. There are usually three grades of lemon-, known as " fancy," " choice." and " standard." The grades depend on the general texture of the fruit, the form, and the color. The sizes vary from 180 to 540 to the box. but few lemons are packed larger than the 240 or smaller than the 490 per box size. The better grades are mostly made up of the fruit of fine texture and of good form picked when green and colored either by slow curing in tents or by sweating. The tree-ripe fruit is less commonly used for the finer select grades, since many question its keeping quality. In some packing houses it goes largely into an inferior grade, and at some seasons of the year when the fruit is quite small from 400 to 500 are packed in a box. A very small percentage of fruit constitutes the grade known as "sinkers," or ''heavy lemons." This type derives its name from the fact that the fruits sink in water when being washed. They are usually spherical in shape and quite small, with extremely thin rinds and a relatively large amount of juice. The green fruit after it is properly cured, either by sweating or by the slower tent process, possesses a rich lemon-yellow color which is seldom found in the tree-ripe fruit. There is a wide variation in the texture of lemons, which is cur- rently believed to be influenced by orchard conditions and the season of the year. As a rule, large, overgrown fruit has a rougher texture than smaller fruit. During the curing process the rind is smoothed down considerably and the texture is improved. Tree-ripe lemons usually have a smoother texture than the green fruit. The rind consists of the external epidermis and a well-developed underlying layer of soft, spongy, white tissue. This layer of tissue contains a considerable quantity of water, much of which evaporates during the curing of the fruit, causing a considerable shrinkage in the thickness of the rind. It is for this reason that the spongy layer [Cir. 26] I "\( rOHS EFFECTING THE KEEPING QUALITIES OF LEMONS. t of the green, freshly picked fruit is, as a rule, thicker than thai of the tent cured lemon-. Individual lemons display great variations in the thickness of their rind, a condition which it is difficult to recognize from the general external appearance of the fruit. It appears that good, sound, normal-sized fruit, with smooth or medium texture, as a rule, has a thinner rind than the rough and oversized sort-. The rind of green fruit varies from one-eighth to five ix teenths of an inch in thickness and averages about one-fourth of an inch. As stated previously, the tent-cured and sweated fruit aver- ages somewhat less, while the " tree-ripes " usually run from one- eighth to three-sixteenths, and "sinkers" vary from about one sixteenth to one-eighth of an inch, <]".<■ to the extreme reduction of the spongy la The seed content of the California lemons is very small, indeed. A large majority of the fruit is entirely free from seeds. Now and then one finds a lemon that contains as many as a do/en seeds, sometimes all developed, but more often only partially so. They occur in all grades and varieties of fruit, but it appears that they arc found more frequently in lemons of low grade. It is said by some growers that orchard conditions as regards the soil and method of cultivation, as well as the general condition of the tree-, have an important bearing on the presence of seeds. It has been noticed that the fruit from some localities displays a greater tendency toward seed production than that from others. The juice constitutes from 30 to :.:. per cent of the total weight of the lemon, varying to a considerable extent with the thickness of the rind and the general solidity of the fruit. In the "tree-ripes," " sinker-." and cured fruit the percentage is higher than in the green, newly picked lemon-, for the reason that the latter have more water in their rind-. The juice obtained by expression contain- a consider- able quantity of mucilaginous material, which gives it a cloudy appearance. Great difficulty i- found in removing this material; in fact, all methods of clarifying tested fail to make the juice perfectly ir. Besides the citric acid, to which the sourness is chiefly due. tar- taric and malic acid- are present, lint in such -mall quantities that they are probably negligible a- to their effect both on the behavior of the fruit it-elf and on the acid determinations. The specific gravity 'Hon juice -how- a narrow range of variation. By far the ma- jority of determinations give results approximating L.035. Numer ou- samples have given result- a- low as 1.026 and still more as high as I.ol. It was expected that the specific gravity of the juice would he governed by the acidity. Inn this was borne out only in a partial way. Ii was found that either a decidedh high or a decidedly low percentage of acid i- indicated by a correspondingly high or low [Clr.2C] 8 FACTORS AFFECTING THE KEEPING QUALITIES OF LEMONS. specific gravity. This was especially true when the arid content was higher than usual. Small differences in acidity are not indicated by the specific gravity with any degree of certainty, the variations in the quantity of mucilaginous material perhaps hiding any change which might otherwise be indicated. Experience has shown that a difference of less than 1 per cent of acid can not he foretold by a specific gravity determination of the juice. CHEMICAL CHARACTERISTICS OF LEMONS. The chemical study of lemons as regards acid, sugar, and water content has been undertaken in the hope that it would lead to in- formation which would offer >ome suggestions for improving the handling and curing of the fruit. ACIDS. The acidity of the lemon is considered by some to be an important factor in determining its keeping quality, it being asserted that lemons containing a high percentage of citric acid resist decay for a longer period than lemons of a lower acid content. The results thus far obtained show the average acid content of the different sorts of fruit calculated as citric acid to be as follows: Percentage of acid in juice. Dark green fruit (picking stage) G. OS Light green fruit (picking stage) (i. 1 i Tent-cured fruit (marketable stage) G. 80 Sweated fruit (marketable stage) 6. !•". Tree-ripe fruit 5. 01 - Sinkers " :.. 68 These results were obtained from a large number of lemons taken from A T arious packing houses and they indicate that there is a differ- ence of a trifle less than 1 per cent of acid between the best keeping grade of fruit, the tent-cured, and the " tree-ripes." which represent the poorest grade on the market. This deficiency seem- too small to account for the marked difference in the keeping quality of these two grades of fruit. Other points of difference much more striking seem to indicate that other factors have a greater bearing on this problem than the acid content. It has been found, furthermore, that tree-ripe lemons showing an average of 6.88 per cent of acid, which is exceptionally high, when stored decay fully as quickly as other fruit of a lower acidity. Sicilian lemons of a good grade bought on (he open market showed on the average 6.45 per cent of acid. This is less than is found in much California fruit of a corresponding grade. In order to determine whether the curing process has any marked influence on the acidity of the lemon, a series of determinations was [Cir. 'JC] FACTORS AFFE< I I ill KEEPING QUALITIES 01 LEMONS. 9 made during February and March, L908, beginning with the time of picking and repeated at weekly intervals until the fruit was ready for market . as I'ulluw - : Percental acid in juice. February •"• ,; - •"■'-' February 10 6. 12 Februarj 17 6. 13 Februarj 24 6.29 March J 6.07 Percentage of acid In juice. March 9 6. 16 March 10. 6. 60 March 23 6.70 March 30 6. 7:: It will be seen that the percentage of acidity shows a tendency to increase, due chiefly, perhaps, to the water loss accompanying the curing process. -i G VRS. The study of the sugars has thus far Keen confined to estimating tlic quantity of reducing sugars in the juice of (he dark green, light green, and tent-cured fruit. An attempt has also been made to trace the development of reducing sugars as the fruit develops in the orchard. The tests which were made during -even stages of develop- ment, the last three stages representing the dark green, light green, and tree-ripe stages, respectively, showed the following percentages of sugar in the juice ; Percentage of SUgar in juice. First stage 1.63 Second stage 1.'_'7 Third stage 1.3S Seventh (tree-ripe) stage Fourth stage . 1. 19 Percentage of sugar in juice Fifth i dark green) stage '-'. 66 Sixth i lighl green i stage 2. 64 2.68 These analyses show that there is relatively little change in the sugar content during the early history of the fruit and that the princi- pal development comes after the fruit has almost reached its full size and i- beginning to ripen. Sugar determinations were also made upon fruit undergoing cur- ing in the curing tents. The estimation was made during February and March. L908, once a week from the time the fruit was picked until the fruit was ready to be marketed. The result- show a very low percentage of sugar compared with the fruit above studied, with no definite trend toward either increase or decrease as the curing pro- ceed-. The following tabulation summarizes the analyses: Percental sugar in Februarj ■". 1.18 February m 1.36 Februarj 17 1. 17 February i'i 1.38 March •_' L 02 Percentage of sugar in juice. March :> |. m March If. 1. 19 March 23 1.09 March 30 i.U - 10 FACTORS AFFECTING THE KEEPING QUALITIES OF LEMONS. WATER ((INTENT. Some investigations were begun relative to the loss of water from lemons while undergoing curing both by the tent-curing method and by sweating. The green fruit as it comes from the orchard has a rather thick rind with considerable spongy tissue. During the cur- ing this tissue shrinks to a considerable extent and the rind becomes somewhat thinned and toughened. This change is believed to be due chiefly to the evaporation of water from the rind. In order to deter- mine the extent of this evaporation, both as to the total amount evaporated and the stages of the curing process during which most of it occurs, a convenient quantity of lemons was placed in a separate box and kept in a tent with about a carload of other fruit and weighed once a week. The lemons were divided into two lots by a partition through the box. the bottom of one-half being lined with paper. This was done with the object of determining the extent to which evaporation is retarded by lining the boxes with paper, a practice which is sometimes resorted to during extremely dry weather. The results obtained during December, 1907, and January, February, and March, 1908, are shown below: Table I. — Loss of water in lemons while curing in tent 31. December 16 . December 23 . December 30 . January 6 January 13 ... January 20... Date. Bi ixes lined with paper. b"\e~ without paper lining. Weekly llivs. I'i r CI at- l.-ll 1.07 .97 1.17 1.45 Total loss. Weekly loss. Percent. I < 1.41 2.47 3.42 4.45 5.97 I II l I ; 1.20 1.64 Total loss. Pel , , n! 1.46 2.55 3.50 4.68 6.23 Table II. — Loss of water in lemons while curing in tent 59. January 27 .. February 3.. February 10 February 17. February 24 . March 2 March 9 March 16.... March 23 March 30.... April 6 llalc. Boxes lined with paper. Boxes without paper lining. Weekly lovS. P< r cent 1.09 . 92 1.10 .87 .'.HI 1.49 1.27 1.50 2.95 2. 30 Total loss. Per ••' nt. 1.09 2.00 3.117 3. M| 4.77 6.2] 7.40 8. 75 11.50 13.59 Weeklj loss. Total loss. 1.04 .97 .98 .99 .97 59 1.30 ,ii 2.77 2. 22 I; r ct nt. 1'' r a a!. 1.04 2.06 8. 23 3. 97 4.94 6. 11 7. 67 9.00 11.57 13.54 [Cir. 2C] FA< rORS \l ! E( I INC THE KEEPING QUALITIES OF LEMONS. 11 The following tabulation shows the percentage of total water loss during twenty-two days from three sorts of fruit: Tabu III. Loss of water in lemons while curing for twenty-two dnj/s. sort ol fruit. Boxes lined B^l 1 ' 1 '- Per cent. Per cent. Dark green Uxlit grreen 2.86 •■ Tree-ripe " 2. 73 ;s. 1 1 These experiments shew thai the loss « •> i" water from the fruit does not increase or decrease week by week with any regularity. Some weeks show a decided increase and arc immediately followed by a corresponding decrease. The explanation for these irregularities can probably be found in existing weather conditions, especially as regards humidity and wind. A wry humid day would cause a decrease in the evaporation from the fruit, whereas a high wind, even though not exceptionally in close proximity to the open side of the house or to door- and corridors where currents of air can circulate around it would necessarily show wider fluctuations in its evaporation than a tent located in the center of the house and well protected from external atmospheric changes. In sweat rooms, where the fruit is kepi at a much higher tem- perature, very differenl conditions are met with. Owing to the high heat with lower relative humidity the evaporation take- place much mole rapidly. The total percentage of water evaporated at different intervals from the fruit in such a -went room, the fruit being sweated twenty days, a period considerably longer than is usually required, is shown lielow : Percentage of water evaporated February •_':: February 25 0.85 Februan 26 i'. 10 Februarj ^7 •_'. Tc Februarj 28 3.40 Percentage of water evaporated. March 1 ::.m March .". i 60 March 'a 6. in March 13 8.05 March Hi 9.25 t l'lr. 26] 12 FACTORS AFFECTING THE KEEPING QUALITIES OF LEMONS. KEEPING QUALITIES OF LEMONS. To anyone who has carefully examined lemons as they come freshly cut from the orchard or as they hang on the tree it is clear that the fruit is oftentimes extremely variable in size, shape, and texture. It is quite generally held that lemons of a certain form are likely to prove good keepers, while those having other forms are liable to decay early. The unsymmetrical, usually undersized lemons grown in the bright sun are thought to be poor keepers, while those from the portions of the tree where the fruits are well enveloped by leaves and have a good size and symmetrical form are believed to have good "life." It has not been practicable thus far to experimentally test these suppositions, but it seems from what has been done that there is a considerable degree of variability in the keeping qualities of lemons from the same orchard and probably from different parts of the same tree. RELATION TO STRUCTURE. Certain structural features, viz. those belonging to the rind, seem to be especially important in this connection. The rind, which con- sists of a layer of white, spongy packing tissue having a very variable thickness, is covered on the surface by the epidermis. This covering consists of a layer of cells so modified chemically as to be almost im- pervious to water. The degree of imperviousness is greatly increased by a dense outer cuticle of a very resistant material which is prac- tically waterproof. There are a vast number of small pores (sto- mata) in the epidermis, through which gases enter and water, as vapor, escapes. These stomata open into small chambers in the outer part of the rind. Additional characteristic structures, known as oil glands from the substance which is formed in them and which they retain until the skin dries up, are found embedded in the outer part of the rind at different distances from the epidermis. The oil in these glands is a volatile product, giving the characteristic lemon odor to the fruit. As has been already indicated, the losses assigned to blue mold are in a very large measure due to the development of the fungus fol- lowing injuries. It is probable that the true blue mold can not pene trate the uninjured epidermis of a healthy lemon, but when a break occurs it is able to enter and bring about the characteristic rot. The development of the defensive outer layers of the rind is a matter of great importance in view of the ease of producing slight, but fatal, injuries to the fruit. To test the strength of this defense, a simple puncture experiment was devised. It consisted essentially of an apparatus so constructed as to enable one to apply known and regulated pressure to a blunt point in such a way as to get the amount of pressure needed to force the point through the epidermis. The needle tip was found to [Cir. 26] FACTORS ' I I I ( II N<: III i: KEEPING QUALITIES OF LEMONS. 13 puncture the epidermis and bring oil to the surface with more readi- ness when it was applied directly over an oil gland —that is, on the surface of one of the projecting papilla' than when applied in the sunken place between these. It appears that the nearer the oil glands are to the surface the greater the ease of rupture. In tree-ripe lemons it seems from the evidence thus far gathered that the outer- most glands are likely to be less protected than in the fruit which is picked green. This would seem to indicate that tree-ripe fruit might -how a greater loss from mold due to injury than fruit picked \\ hile green. In a similar study of tent cured fruit, a resistance markedly greater than in tree-ripe lemon- was shown, indeed, the resistance to punc- ture in tent-cured fruit seems to be double that of tree-ripe lemon-. This difference is probably (\\io in part to other factors than the absolute strength of the wall- of the epidermis, hut the result rep resents practically the relative liability to damage dependent on the structure of the outer tissues of the lemon. It was found that lie' tissue beneath the tough outer epidermis was able to offer very little resistance when the point of a needle hail passed through the epidermis. Lemons are frequently subjected to steady pressure of various degrees of intensity, and are preserved from injury by the general strength of their tissues throughout. Under these circumstances, the white, pulpy packing tissue between the epidermis and the segments play- an important part. The thickness of this tissue varies very widely. In the so-called "•-inker-." which form a case of an extreme reduction, this tissue forms a very inefficient protection against in- jury. Hence, ''sinkers " might !"■ expected to he poor shippers. ii \ 1 1 1 1 1 . The relation of coarseness of texture to losses is not very clearly marked. In general, coarse lemons have a strong development of rind tissue. But many smooth lemon- are equally well protected. The thickness of the epidermis and the consequent ability of the lemon to withstand wear i- well tested in the box during shipment, w hen. as frequently happens, the jar of the car in stopping and start ing is transmitted to the fruit in the box. The resull follow- that the fruit i- •• rasped " on rough surfaces of the shook, particularly of the end- and middle crosspieces when they are not planed. Ml I IK 'li ol (1 in M.. Tin' keeping qualities of different types of lemon- also depend largely on the method of treatment to which they are subjected to bring them into marketable condition. Although the inh< on- dition of the fruit, ^\\\r partly to its early history, will determine rcir. 20] 14 FACTORS AFFECTING THE KEEPING QUALITIES OF LEMONS. its ability to resist decay to some extent, there is reason to believe that the method of curing is an important factor in determining the life of the lemon on the market. The lemon growers as a rule agree that the so-called sweating process of curing fruit has a deteriorating effect, although no definite test< have been made which would fully substantiate this belief. The sweating process is resorted to only when the briskness of the market necessitates a rapid coloring of the fruit. The grower, although he realizes the possibility of endan- gering the quality of his fruit, has at present no other method of curing lemons rapidly, and is therefore compelled to make the most of the process. The tree-ripe fruit, as has been stated elsewhere, is thought to be inferior to the tent-cured sort, and is kept in the packing house as short a time as possible. After being washed and graded, it is immediately put upon the market, as a rule, for unnecessary delay in the packing house will only shorten its life on the market. The point to be investigated, therefore, is the relative keeping qualities of these three sorts of fruit. With this object in view, a limited series of storage tests was made in the spring of 1908. All the fruit was shipped to Washington, D. C.. and stored. The entire lot was carefully examined once a week for three or four weeks, and then every two weeks during the remainder of the test. Careful note was made of the form of decay which was met with, in order to get more information as to what varieties of decay are most destruc- tive after the fruit arrives on the market. The following are the summarized results: Table IV. — Loss nt lemons from all forms of decay during sijctei n Wi < ks in storage. No. of Int. Tent-cured fruit. ripe fruit. Sw eared fruit. 1 I'l r C< :;! 11.5 19 ■A A;' <■/ lit. I,.-. (1 49. 7 54.0 9 i j$9 ii I'< r a i'l 72.0 23.1 5 " Two weeks lessi Table V. — Percen ag( -< otal loss of lemons due apparently to blue mo No. of lot. Tent-cured Tree-ripe fruit. fruit. i'i !• i Per • n 18.5 17.6 52 .1 i.; 8 76.0 46.3 Sw eated fruit. 72.0 62. - o In these fig Hrst two weeks in torage are not included, tor l lie different forms oi di i were not registered separately. During the early weeks the blue mold predominati d ow ing perhaps to the mechanical injury received in the packing house and in transit. [Cir 26] I it CORS EFFECTING THE KEEPING QUALITIES OF LEMONS. L5 A careful study of Table 1 \' will indicate clearly the superiority of the tent-cured over the tree-ripe fruit. In each of the five lots this point is well brought out. It will be further noticed that the amount of rot in the tent-cured fruit is very nearly the same in all five lot> (if lot 5 had been kept two weeks longer it would probably have -how ii nearly 30 |>er cent of deca\ ), thus showing that there is no material difference in the fruit which had been obtained from the coast, the foothills, and the inland districts. I he results obtained from sweated fruit indicate a rather peculiar condition, which it is impossible to explain at present. Neither lot weated as thoroughly as is the custom, nor were both lots sweated exactly alike, which facts may account to some extent for the great difference in the result-. The variation in decay is not the only point, however, in which these two lot- of fruit differed. Lot 3 was excellent fruit, with a soundness, texture, and color well worthy id' the best fancy grade, while lot •_' was. almost from the beginning of the tests, of such unpresentable appearance as to make it practically unmarketable. The causes underlying these great differences are not understood at present, hut the results "unite a more extended study of the matter. THE MOST SERIOUS CAUSES OF DECAY OE LEMONS. An important phase of the whole situation as regards keeping qualities is the matter of the different forms of decay met with in these tests. In the first few examination- no definite record was kept of each form, hut the blue mold predominated, a condition which lie. nine- prevalent after much handling of the fruit, a- i- the case in sorting, packing, and shipping. After a few week- it became appar- ent, however, that a different form of decay was beginning to appear, which suggested the necessity of keeping a close watch on the relative growth of each form. Table V -how- the percentage of the total rot which was apparently due to blue mold when -i'rw. Considerable difference is found among (he various lots. The amount of care exer- cised in handling the fruit at tin' different place- where it was obtained and the fact that it was not all shipped over the same route might go far in explaining the di fference. A- many a- five apparently distinct types of slow disease id' the rind were -ecu. oftentimes having very striking form and color char- acteristics. These were not studied, since, apart from injured appearance, the loss due to them directly appeared to he hut -mall. They may. however, posses greater significance by opening the way for the more actively destructive power- of the mold. Finally, there is a \er\ prevalent form of decay resembling in appearance and in odor the virulent brown-rot of the citrus region. [Cir. 26] 16 FACTORS AFFECTING THE KEEPING QUALITIES OF LEMONS. The conspicuous symptom is a brownish discoloration, which may appear anywhere on the lemon, followed by softening, discoloration, and a spreading of the affected area, which in time involves the entire lemon. The progress of the decay can be noted by the brown color and disintegration of the tissue-. The following table shows an interesting condition a< to the periods when the greatest and smallest amount of decay takes place : Table VI. — Decay in lemons in storage for different periods. in storage. Lot 1. Lot 2. Time Tent-cured fruit. Tree-ripe fruit. Tent-eured fruit. Tree-ripe fruit. Sweated fruit. Per a nt. 1.6 2.9 2.2 1.8 3.1 ::. 2 5.0 7 2 8. l 14.0 13.4 !'• i cent. 10.0 17.4 5.5 1.0 I E 12.6 14.9 16.5 15. 3 Per n ill. 0.0 .5 1.9 .0 .4 .0 1.5 2.7 2.0 5.4 (i.l /•• r cent. 5. 1 6 3.5 2. 2.2 1.4 6.8 6.8 12. 2 11.0 /■< r cent. 3.1 1 1 ,.7 2 13.2 ;i 3.4 4 3.6 6 3.7 8 2.2 10 16.3 12 21 8 14 19.6 16 27.7 Lot 3. Lot 4. Lot 5. Time in storage. Tent-cured fruit. Tree-ripe fruit. Sweated fruit. Tent-eured fruit. Tree-ripe fruit. Tent-cured fruit. Tree-ripe fruit. Weeks. On arrival 1 Perct n(. 0.0 3.3 .0 .6 .8 2.4 3.9 5.1 7.:: 8.6 14.2 /■- r '■'Hi. O.S 2.8 .0 .0 .3 .9 5.8 9.0 7.8 14.0 11.2 /'. r a nt 0.0 2.1 1.0 .7 1.1 .0 2.9 1. 12 3.4 1.9 2. 1 Perct nt. 1.2 1.3 4.3 2.2 .5 1 - 2.3 4.8 4.5 7.4 9.7 Per a 4.8 1.2 3.0 4. 9 4.2 3.9 22. 1 17.:; 27. (', /'i r a hi. 2.8 6.8 1.8 .9 .4 1.4 .9 3. 3 3.5 1.1 Per < 4.1 8.8 2 2.7 3 1.6 4 1.2 6 2.8 8 2.1 10 4.4 12 t;, 3 n 13.0 16 The principal tiling to be observed here is the interval of minimum decay occurring about three or four weeks after the arrival of the fruit in storage. After this more or less extended period the decay often increases rapidly from week to week. When it is remembered that the decay during the first few weeks was mainly due to blue mold, it seems reasonable to suppose that the period of decreased decay follows after the majority of the fruit injured mechanically during curing and packing and while in transit has succumbed to the attack of the blue-mold fungus. In other words, it constitutes the period of the greatest freedom from any form of decaj^. The fruit later shows signs of weakening, however, and collapse, the symptoms of which have already been discussed, then becomes the chief source [Clr. 26] FACTORS EFFECTING THE KEEPING QUALITIES OF LEMONS. 17 of loss. The lemon thu^ weakened again offers an opportunity for blue-mold attack. It must be remembered that these observations were made on tests of a comparatively small quantity of fruit. Ex periments along i h is line will be continued on a larger scale. CONCLUSION. From the work thus far accomplished certain general conclusions seem to follow, but in indicating them it should be distinctly borne in mind that they are advanced in a tentative way and may be more or less modified as these investigations progress. It is probable that the keeping quality of American fruit in the market is affected by the manner of handling in the course of its history, especially during the later stages of handling in California, during transit, and in the whole-ale houses. Rough handling results largely in cases of blue mold. A well-marked physical breakdown, resulting apparently from brown-r >t infection, seems to cause most serious losses after the fruit has been stored for some week- or months. Tn a series <>( experiments designed to demonstrate the communi- cability of this disease under the condition- of storage present, nega- tive results at first seemed to point to a physiological breakdown, but a study of the decaying lemon- by Mr-. Flora W. Patterson. Mycolo gist of the Bureau of Plant Industry, revealed the presence in practically all cases of fungal hyphse resembling those of Pythia- cystis, tin' brown-rot. Investigations in the office of Fruit-Disease [nvestigations, under the direction of Mr. M. B. Waite, Pathologist, have demonstrated the presence in much of the diseased fruit of the wither-tip organism, Colletotrichum. One or both of these organisms, and perhaps other- also, are therefore apparently the cause or causes of the brownish rot which appears in the lemon- after they have been some week- in storage. Infection probably takes place in Cali- fornia and the disease remains undeveloped until week- after arrival in the eastern market. Approved : James Wii son, Seen tary of . \.gricultiin . Washington, D. ('.. May J',. 1909. O ' croi i t ut- hL UKIUA 3 1262 08928 9499