142 MANUAL OF FRUIT DISEASES 



under conditions of storage approximating those last enumer- 

 ated, the brown-rot mummies are shiny and jet black. In any 

 case the interior of the affected fruit is brown and soft. It 

 has been stated elsewhere (page 140) that brown-rot and black- 

 rot are sometimes confused. The following external charac- 

 ters serve to distinguish the two diseases : (1) Apples affected 

 with black-rot are at first brown, and sometimes remain so, 

 but more often become black, and the surface is dotted with 

 minute black pustules. These characters are sufficient to dis- 

 tinguish brown-rot from black-rot. (2) Apples affected with 

 black-rot shrivel rapidly, become greatly reduced in size and are 

 considerably wrinkled. Apples affected with brown-rot do not 

 shrivel greatly, are not appreciably reduced in size, and are 

 much less wrinkled. (Figs. 10, 11 and 37.) 



Cause of brown-rot. 



The apple brown-rot pathogene, Sclerotinia cinerea, is a 

 fungus which has been confused with Sclerotinia fructigena, 

 the organism causing brown-rot of pome-fruits in Europe. 

 Both species may attack both stone- and pome-fruits, but 

 >S. fructigena invades chiefly pome-fruits in Europe, while 

 S. cinerea is the more common form in America. It is 

 doubted that the European S. fructigena occurs in this 

 country. The habits and structures of the two organisms are 

 very similar. 



Hibernation occurs chiefly as mycelium in the hanging mum- 

 mies. In the spring conidia are liberated from tufts developed 

 from the over-wintering mycelium. As the fruits come to 

 maturity the conidia, falling into wounds on the fruit, germinate, 

 and finally cause brown-rot. In the autumn many affected 

 fruits fall to the ground ; others hang on the tree over winter. 

 It is the latter class which plays the important role in carry- 

 ing the fungus from fall to spring. The history of the fallen 

 mummies is not known; whether a sexual stage ultimately 

 develops from them has not been definitely shown. It is 



