siderable decay, but none of the berries so treated developed into typical leaks within 48 hours after removal from the refrigerated container, and the presence of black dirt in the wounds was misleading and made the accurate sorting of these berries difficult.

The above experiments indicate that the fungus in question is not of primary importance as a field rot, that usually it does not enter the berries from the soil, and that in the localities investigated infection occurs at some time after picking.

UNSANITARY CONDITIONS USUALLY PREVAILING IN THE PACKING HOUSE.

Conditions in and around the packing house often are unsanitary, favoring the growth and distribution of Rhizopus, and the frequent handling and consequent bruising which the berries often undergo would seem to offer many chances for infection. The culls often are thrown on the ground near the packing house; various fungi, including Rhizopus, may be found fruiting on these discarded berries. Packing tables become soaked with strawberry juice and usually are not cleaned or disinfected during an entire season. When berries are washed, a few gallons of water are placed in a tub and used for all berries cleaned during the day. Fungus spores, soil, and other dirt soon accumulate in this wash water, and apparently might by this means be distributed generally over a large proportion of the fruit.

Conditions in packing houses and cars as regards infection from Rhizopus can be easily improved by the frequent use of hot water. The recent work of Thom and Ayers (16) shows that the spores of this fungus are easily killed by heat when wet, but are more resistant in dry air. Rhizopus spores (16, p. 159) were killed in 30 seconds at a temperature of 145° F. in milk, but survived a temperature of 200° F. when dry. It is probable, however, that even with the greatest care all sources of fungous growth and distribution can not be eliminated.

THE BRUISING OF BERRIES IN PACKING.

It has been shown that Rhizopus rarely, if ever, enters berries through the unbroken epidermis; care to avoid bruising is therefore of great importance. This fact was emphasized by an experiment in which sound berries were wrapped individually in tissue paper, carefully packed, and shipped to Washington. It was found that fruit so treated could be held at room temperature for a week or more after arrival without the appearance of decay, while similar berries packed and shipped in the commercial manner were badly rotted within 48 hours after reaching their destination.

Berries are injured to some extent every time they are handled or shaken. When possible, especially when shipments are made in car lots under refrigeration, it is preferable to ship in the containers in

which the fruit is picked without further handling. However, fruit shipped in crates without refrigeration or in pony refrigerators, as from Florida, usually suffers severely by careless handling at points of transfer. In these cases the close packing of the fruit to prevent settling has been found to be of much advantage. If packed too tightly or forced into place, the fruit is unnecessarily crushed and bruised. The aim of the best packers is to place the berries as closely as possible without crowding or injuring them.

DIRECT SOURCES OF INFECTION.

One experiment was conducted in which the berries were treated in various ways to obtain, if possible, some indication as to the most serious sources of infection with Rhizopus in commercial handling. Apparently sound berries were selected, and in order to accentuate the comparative value of the results obtained the epidermis of each berry (except in A and C, Table I) was broken with a sterile needle before other treatment. All berries were then packed similarly and shipped in small iced containers. The results of the experiment are given in Table I.

TABLE I.-Infection of strawberries resulting from various methods of treatment.

E.-Washed in water used in packing house.

F.-Dirt forced into the wounds.

G-Rhizopus mycelium forced into wounds.

H.-Washed in water containing spores from a pure culture of Rhizopus..

Table I shows that injury with pine needles and washing in clean water did not injure the shipping qualities of the berries any more than did injury with the sterile needle. The contrast between the final condition of fruit washed in clean running water and that washed in the ordinary commercial manner was most striking. This preliminary shipment gave a valuable clue, which was followed in subsequent experiments. In all later shipments sound, unwounded berries selected individually by one of the writers or those selected by careful professional packers were used.

WASHING BERRIES.

The influence of washing upon the development of rot in strawberries was investigated. In each of a series of shipments made in small iced containers, commercial pony refrigerators, or ventilated

crates without refrigeration, some of the berries were washed in the tubs of water which had been previously used for the washing of several bushels of commercial berries, some were washed in clean running water, and the remainder were not washed. All washed berries were dried for a few minutes in the shade. They were then packed by professional packers (all berries in each shipment being packed by one operator) and sent to Washington, where records were taken upon careful inspection of each berry. The results of these experiments are summarized in Table II.

TABLE II.-Infection resulting from washing strawberries in a commercial

The generally low average of sound fruit was due to the length of time the berries had been kept at room temperature after reaching their destination. In northern markets, however, one frequently finds berries which contain no higher proportion of sound fruit. The results given in Table II indicated that the commercial method. of washing berries was injurious to their shipping qualities and also that this injury would be largely overcome by the use of clean water. The frequent changing of water in the tub usually would not be inconvenient in Florida, for wells and pumps often are located. at or near the packing houses.

DRYING BERRIES AFTER WASHING.

As already mentioned, a few growers make a practice of packing their fruit wet, though most of them expose it to the air, either in the shade of the packing house or, more frequently, in the sun, until most of the water has evaporated from the surfaces of the berries. Experiments were undertaken to determine the relative effects of these different methods from the standpoint of inhibiting the growth of Rhizopus in the fruit.

When berries are dried they are spread upon cloth-covered frames or packing tables. These cloth covers usually are not renewed during a shipping season. Often they are soaked with juice from the strawberries, and it was suspected that they might serve as carriers of infection to fruit spread upon them. Numerous careful experiments for the determination of this point, however, gave

negative results, indicating that any increase of infection from this source is relatively unimportant.

In investigating the effect of drying the fruit after washing, a number of experimental shipments were made, the fruit being handled in the same manner as in the washing experiment already described except that part of the berries in each shipment were packed wet, while the remainder were partially dried, usually by exposure to direct sunlight for a few minutes. The results were conclusively in favor of packing the fruit wet. Taking the average of all these experiments, it was found that drying berries washed in clean water had reduced the proportion of sound fruit 36 per cent. Among those washed in dirty water the reduction caused by drying was even greater 43 per cent.1 Table III summarizes the results of all experiments on drying the berries after washing.

TABLE III.—Effect of drying strawberries after washing.

In no case were these results reversed, though they differed in degree in the various shipments. These variations were correlated with differences in temperature when the berries were packed, the comparative benefit of wet packing being greater in those shipments prepared on very warm days than in those packed during cool, cloudy weather. Drying the fruit, even in the shade, proved injurious, though less so than exposure to direct sunlight.

The laboratory experiments already cited indicate that the rate of growth of Rhizopus nigricans increases very rapidly with the rise of temperature above 10° C. (50° F.). When infected berries are held. for a few hours at a relatively high temperature, for instance, 30° C.

1 Smith and Goodman, of the Department of Agriculture of British Columbia, have conducted experiments upon the fanning of strawberries before shipment. They report (Winslow, R. M. Report of horticultural branch, 1914. In 8th/9th Rpts. Dept. Agr. [Brit. Col.], 1913/14. p. 84. 1915.) that berries dried for an hour in a strong current of air from an electric fan carry to market in better condition than those shipped even slightly wet. Though not so mentioned in their report, this operation would have the effect of lowering the temperature of the berries quickly and considerably by increasing the rate of evaporation of the water from their surfaces. It would thus be, in effect, a precooling process, allowing the berries to be placed in the car at a relatively low temperature if loaded at once; if, after fanning, however, the fruit were hauled several miles to the station during hot weather, much of the benefit of rapid drying would be lost.

(86° F.), the fungus develops so rapidly in their tissues as to cause them to collapse. The growth of the fungus may be checked by lowering the temperature, but with ordinary refrigeration growth will not entirely cease, and it may continue sufficiently to cause the berries to soften in transit; it will in any case resume rapid development whenever the temperature is again raised, as when the berries reach their point of destination. If infection has occurred, a difference of a few degrees in the temperature of the berries, maintained for several hours, will make a decided difference in the length of time before rot becomes apparent. This accounts for the harmful effects of drying the berries.

Dry berries remain at air temperature until placed in iced cars or other refrigerated containers, usually a period of several hours. During part of this time the crates are often exposed to the sun or covered with a dark cloth. When berries are immersed for a few seconds in water their temperature is lowered somewhat. Subsequent evaporation from their surfaces results in still further cooling. If they are packed immediately after washing, evaporation continues slowly and exerts a cooling effect for several hours, usually until the berries are placed under refrigeration. When berries are being loaded into cars in the afternoon, several hours after picking, the difference in temperature between unwashed fruit and that packed wet can be readily felt with the hand. When, after washing, the berries are dried for a few minutes in the shade, the water evaporates before packing, and they lose the continued cooling effect of prolonged evaporation. If they are exposed to direct sunlight there is the added disadvantage of a further rise in temperature. The beneficial effect of packing the berries wet is greatest, of course, when the temperature of the air is highest.

Professional packers claim that berries are softened by washing and must be handled with great care to avoid bruising if packed while wet. This probably is true, but it is more than compensated for by the cooling of the fruit.

Exposure to sunlight, unless very brief, has the further undesirable effect of giving the berries a dull appearance. Heating unwashed berries by exposure to the sun increases rot, but not so markedly as with washed berries. This is illustrated by an experimental shipment prepared at Lakeland, Fla., on the morning of March 22, 1916, a clear, warm day. Sound berries of the Missionary variety were used. After treatment they were packed by a professional packer, carried to the railroad station at noon, and shipped to Washington in a ventilated crate without refrigeration. They were three days in transit. Their condition on arrival is shown in Table IV.