350 TEXT-BOOK OF FUNGI 



belonging to the heterogeneous collection of conidial forms 

 included in the ' Fungi imperfecti.' Zygodesmus differs 

 from Hypochnus in the less differentiated basidia bearing 

 a variable number of sterigmata. Clamp-connections are 

 very conspicuous on the hyphae. All the other genera 

 included in the Thelephoraceae have a typical compact 

 hymenium. In two genera, Coniophora and Corticium, 

 the thin sporophore is resupinate or attached by its entire 

 under sterile surface to the substratum. The hymenium 

 in both genera is perfectly even, and there are no cystidia. 

 There is also an absence of a subhymenial layer, that is, a 

 compactly interwoven zone of hyphae situated between 

 the lower vegetative hyphae of the sporophore and the 

 hymenium. In all other genera included in the Basidio- 

 mycetes this subhymenial stratum is present, and gives 

 origin to the basidia. 



Next follow in order the genera Peniophora and Hymeno- 

 chaete. The simplest types in both genera are entirely 

 resupinate as in Corticium, but in the more advanced 

 species the uppermost portion of the sporophore becomes 

 free from the matrix, and projects at right angles to it, the 

 hymenium being on the under surface of the free portion 

 of the sporophore, and pointing to the ground. In both 

 genera the hymenium is perfectly even, and densely 

 crowded with cystidia. In Peniophora the cystidia are 

 colourless, thin-walled, and eventually become rigid, due 

 to a superficial crust of amorphous particles of lime. 

 When young the cystidia appear to act as organs of 

 transpiration ; very minute drops of water containing the 

 lime salt in solution are liberated by the cystidia, and as 

 the water evaporates, the lime is deposited as a solid, super- 

 ficial crust. By this means the cystidia are rendered very 



