RHIZOPUS EOT 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 (4) 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- 

 eans 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 Ehizopus. 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 

 malus). Behrens (2) found it causing rot of tomatoes (Lycopersi- 

 eon esculentum) and was able to produce decay by inoculation in 

 pears (Pyrus), plums (Prunus), raspberries (Rubus), and currants 

 (Ribes). Wormald (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 (Tpomoea), although Halsted (7) 

 80315°— Bull. 531—17 -2 



