144 



PLANT DISEASES 



Rhytisma salicinum, F., forms large pitchy-black patches 

 on leaves of goat willow (Salix capreae, L.) and several 

 other species of willow (Salix). 



CLOVER LEAF SPOT 



(Pseudopeziza trifolii, Fckl.) 



A fungus that not unfrequently proves destructive to 

 crops of lucerne (Medicago sativa) and clover (Trifoliuni). 

 The leaves are attacked, and first show minute blackish 



Fig. 29. Pseudopeziza Irifolii. i, a clover leaf badly diseased, 

 nat. size ; 2, a pustule or fruit of the fungus bursting through 

 the epidermis of the leaf, which is torn into triangular teeth, 

 slightly mag. ; 3, an ascus containing eight spores, also two 

 paraphyses, X 400. 



specks on the upper surface; these increase in size and 

 extend through the substance of the leaf, showing on the 



