438 COMPARATIVE MORPHOLOGY OF FUNGI 



an important role in the dissemination of the fungus. They are prob- 

 ably homologous to the hymenial bulbils of Rhacophyllus lilacinus. In 

 other species, e.g., Peniophora chordalis, the cystidia stand far above the 

 hymenium (Fig. 281). In P. chaetophora, they are branched and project 

 above the hymenium in the form of setae, serving as a support for the 

 outer, loose hymenium which creeps up them (Fig. 282). When young, 

 they are binucleate; after the degeneration of the nucleus they contain 

 only a clear content. In many species they are covered with calcium 

 oxalate. 



As imperfect forms, conidia have been demonstrated in Corticium and 

 Peniphora (Kneiffia) (Lyman, 1907; Hoehnel and Litschauer, 1906). 

 In C. radiosum, they arise (occasionally on the clamp-bearing mycelium 

 itself) on short, characteristically branched conidiophores and are bacilli- 

 form or oidia like. In C. roseopallens, they are usually cut off in tufts on 

 short branches and are slightly curved. In C. effuscatum, they arise on 

 the hyphae or on capitate swollen conidiophores, and are spherical, these 

 capitate conidiophores correspond to the Oedocephalum type in the 

 imperfects and are again met among the Polyporaceae in Fomes (Fig. 288). 

 In Peniophora coronilla the conidia are cut off in groups of eight on short 

 sterigmata and appear, externally, very similar to the basidiospores. 

 In Corticium effuscatum and C. subgiganteum are formed thick-walled 

 gemmae. In the latter species they appear subterminally on palisade 

 hyphae and may then be regarded as a highly specialized gemma hymen- 

 ium. This gemma fructification was earlier considered as a separate 

 species. Similarly, the gemmae of Peniophora Habgallae were described 

 as Artocreas poroniaeforme and Michenera Artocreas (Petch, 1926). 

 Corticium niveocremeum has six-spored basidia of which two spores abort, 

 since only four nuclei are formed in the basidium, and the four fertile 

 spores are uninucleate (Kuehner, 1926). 



Hymenochaete belongs to the third stage of development. As the 

 name indicates, this genus is characterized by the presence of elongate, 

 conical, brown setae, which blacken promptly with a solution of 

 KOH. The setae are arranged in layers often suggesting annual rings 

 (Burt, 1918). Hymenochaete is predominantly tropical with a rapid 

 decrease of number of species in the temperate regions. In these, the 

 Corticiaceae reach the highest stage of development. Their fructifica- 

 tions are leathery, woody or corky. Stereum also begins with simple 

 resupinate forms, gradually raises its edges from the substrate, and 

 extends horizontally, becoming laterally attached brackets and simple 

 stipitate fructifications. S. hirsutum and S. fasciatum are instructive 

 examples of the dependence of the form of the fructification on its 

 position on the substrate. In horizontal substrates the fructifications 

 are resupinate with up-turned margins, radial in structure with the 

 hymenium downwards. On vertical substrates they extend horizontally 



