THE FUNGI WHICH CAUSE PLANT DISEASE 



403 



Key to Genera op Hypochnaceae 



Spores colorless, smooth, rarely granular 

 Basidia with two sterigmata 



Basidia circinate 1. HeUcobasidium. 



Basidia not circinate 



Basidia pyriform, beaked 2. Urobasidium. 



Basidia clavate, not beaked 3. Matruchotia. 



Basidia with 2-4 rarely 6 sterigmata 4. Hypochnus, p. 403. 



Basidia with numerous sterigmata 



Sterigmata small 5. Aureobasidium, p. 405. 



Sterigmata large 6. Pachysterigma. 



Spores colored, mostly spiny 7. Tomentella. 



Hjrpochnus Ehrenberg. 



Floccose or fungoid, rarely thinly fleshy, spreading over the 

 substratum; basidia clavate; spores colorless, smooth or minutely 

 granular. 



This genus which contains half the species of the family, is 



Fig. 290. — H. ochroleucus sporogenous reticulum prior to spore formation. 

 8 basidia, sterigmata, and spores. After Stevens and Hall. 



with difficulty distinguished from Corticium from which it differs 

 in the character of its hymenium. 



H. ochroleucus N. **"'^ Sporogenous reticulum of a very close, 

 irregular net work of hyphae variable in thickness; basidia scattered, 



