410 



THE FUNGI WHICH CAUSE PLANT DISEASE 



S. purpureum Pers. 



Hymenophore expanded, leathery, arched, grayish-white; hy- 

 menium smooth, purple. 



This species is constantly associated with an English and Cana- 

 dian disease of drupaceous and pomaceous trees, manifest by a 



Fig. 295. — Oak timber rotted by Stereum frustulosum. The 

 lighter colored, irregular, small bodies are sporophores. After 

 von Schrenk and Spaulding. 



silvering of the leaves, death of branches and finally of the tree. 

 The causal agency of the fimgus has not been fully established.*' 



Cosmopolitan in distribution. 



S. rugosum Fr. parasitizes the cherrj^ laurel. 



Thelephora Ehrenberg (p. 406) 



Hymenophore leathery, context similar, variable in form, 

 sessile or pileate, even or more commonly plicate; hymenium con- 

 fined to the lower surface or extending all over the hjTneno- 

 phore, smooth or uneven, sometimes warty; basidia numerous, 

 clavate; spores elongate, membrane often dull brown, and granular. 



