ASCOMYCETES 



205 



Distribution and occurrence. This anthracnose is a disease well 

 known in Europe and America. Periodically since 1 884 it has been 

 mentioned as a destructive fungus to both white and red currants 

 in New York. The fungus 

 has also been found upon 

 black currants and goose- 

 berries, but it has never, 

 apparently, amounted to an 

 epidemic. Among red cur- 

 rants Stewart observed that 

 Prince Albert and President 

 Wilder were practically free 

 from injury where Fay's 

 Prolific and Victoria were 

 seriously affected. 



Affected leaves are more 

 or less covered with small 

 brown spots, as shown in 

 Fig. 158. When the trouble 

 is serious the leaves turn 

 yellow and drop. The fun- 

 gus also occurs on petioles, 

 young canes, fruit stalks, and fruits. It is believed that it may 

 pass the winter on the canes. 



The fungus. Until 1906 this fungus was known by an im- 

 perfect stage alone, which like that of the bitter rot of the apple 

 subsequently discussed was referred to the genus Glceosporium, 

 and bore the name Glceosporium Ribis. The Glceosporial stage 

 (cf. Glceosporium) is in fact the only stage of the fungus which is 

 produced upon the growing plant. The pustules or acervuli con- 

 sist of a stromatic portion from which arise numerous conidiophores, 

 bearing elliptical or strongly curved, falcate conidia. These fruit- 

 ing masses rupture the epidermis and the spores escape in a gelat- 

 inous mass. The acervuli are produced very abundantly on both 

 surfaces of the leaves but particularly upon the upper surfaces. 

 The spores are commonly 19 x 7 p, varying, however, from 12- 

 24 x 5-9 fi. Formerly, it was suggested that this glceosporial form 

 might be connected with Gnomoniella circinata (Fckl.) Sacc. 



^CDOOOOOOOCOC 



Fig. 78. Pseudopez/za Medicaginis: 

 Structural Features. (After Comes) 



