RHIZOPUS ROT OF STRAWBERRIES IN TRANSIT. 9 
point of inoculation. Several boxes of commercial berries kept at 
10° C. for one week showed about the same proportion of decayed 
berries as similar boxes kept at room temperature for 12 hours. Very 
little work was done on the investigation of temperatures above 20° 
C. The fungus appears, however, to be able to mature a few spo- 
rangia with short stalks on ripe strawberries at 36° to 37° C. From 
these experiments it appears that a temperature of 10° C. (50° F.), 
or, better, 8° C. (46° to 47° F.), is satisfactory for preserving straw- 
berries from this fungus for a week or more. The rate of growth of 
this fungus increases so rapidly with rise of temperature above this 
point that the importance of keeping the berries at this temperature 
is obvious. 
In this connection it is of interest to note that Earle (1) in his 
shipping experiments found that 50° F. was satisfactory for shipping 
strawberries. 
HOST RELATIONS. 
From microscopic study (13) it is apparent that Rhizopus nigri- 
cans is unable to penetrate the sound epidermis of the strawberry. 
Additional evidence as to the correctness of this view is found in 
the results of experiments in which wounded and unwounded berries 
were sprinkled with spores of Rhizopus. The wounded berries in all 
cases rotted quickly and bore typical sporangia, while the unwounded 
berries remained uninfected. 
Inoculation experiments in field and laboratory show that Rhizopus 
is able to grow in green strawberries and produce typical leak if 
the epidermis is wounded. On February 21, 1916, green berries 
shipped from Florida were wounded and inoculated with Rhizopus. 
Two days later all these berries had developed mature sporangia. 
Ten similar berries, unwounded, over which spores of Rhizopus were 
sprinkled showed no change. While still on the vines 100 green 
berries were wounded and inoculated with Rhizopus mycelium from 
a pure culture. All of these developed the typical Rhizopus rot, 
most of them before maturity. 
OCCURRENCE ON OTHER PLANTS. 
Rhizopus nigricans has been noted frequently as the cause of rot 
in various vegetables. Ehrenberg (5), in connection with his 
original description of the genus, mentions its occurrence on decay- 
ing fruits of Cornus masculus, Morus alba, and once on apple (Pyrus 
mains) . Behrens (2) found it causing rot of tomatoes (Lycopersi- 
con esculentum) and was able to produce decay by inoculation in 
pears (Pyrus), plums (Prunus), raspberries (Rubus), and currants 
(Ribes). Wormalcl (17) and Hanzawa (8) report it as causing a 
decay of tomatoes. In this country it is probably best known as 
causing a rot of sweet potatoes Qpomoea), although Halsted (7) 
80315°— Bull. 531—17 2 
