344 



THE BASIDIOMYCETES 



noid or loosely compacted subiculum. Its Rhizoctonia solaiii 

 stage may form compact brown sclerotia capable of withstand- 

 ino^ long periods of unfavorable weather. Cortichnn koleroga is 

 equally widely distributed in tropical and subtropical regions and 

 produces thread blight of leaves, fruits, and twigs of many species 

 of trees and shrubs. Its mycelial stage also belongs to Rhizoc- 

 tonia, and sclerotial formation is in part determined by whether 



W 



A B C D E F G H I 



Fig. 130. Diagrammatic representations of stages in transformation of a 



dicarvotic hvphal tip into a basidium. 



the host tissues have a roughened surface. iMost species of Corci- 

 cium have a papery to leathery hymenophore and lack the Rhi- 

 zoctonia stage. Peniophora is quite like these kinds of Corti- 

 cium, but awl-shaped cystidia are interspersed among the basidia. 

 In the southeastern United States P. gigantea is one of the im- 

 portant fungi involved in the decay of pine pulpwood stacked in 

 yards. Coniophora cerebella also causes dry rot of coniferous 

 wood throughout North America. 



Thelephora fimbriata and T. terrestris grow up from the soil 

 of nursery beds and smother or strangle tree seedlings. They 

 seem unable to penetrate living host tissues but are able at times 

 to cause serious losses in forest-tree nurseries. 



Stereum is among the larger genera. Burt (1920) lists 80 



