120 RESEARCHES ON FUNGI 



Polyporus hispidus, Fomes applanatus, etc., by spreading out its 

 hymenium in deep tubes attached to a single very large fruit-body. 

 The dispersal of the hymenium on many closely placed small pilei, 

 rather than its concentration upon one very large pileus, is also 

 to be observed in the bulky fruit-body masses of Hydnum septen- 

 trionale and in Polystictus versicolor, Polyporus radiatus (Fig. 42), 

 P. adustus, Stereum hirsutum, etc. In the four last-named species 

 the fruit-bodies are rarely, if ever, solitary ; and often a score or 

 more of them cover an extensive area on the side of an old tree- 

 trunk or a stump. The pilei individually are small ; but this 

 finds a compensation in their large number. 



Certain Polypori, e.g. Polyporus giganteus, P. umbellatus, P. 

 frondosus, of which illustrations will be provided in Volume IV, 

 have branched or compound fruit-bodies, one central stipe bearing 

 many pilei. The compound condition of these fruit-bodies seems 

 to be correlated with the fact that the species in question are 

 terrestrial. The stipe grows upwards from the ground, branches 

 and rebranches, a large number of small more or less imbricating 

 fruit-bodies thus coming to be produced in the end about a central 

 supporting axis. As in Polyporus sulphureus, these fungi, so to 

 speak, have solved the problem of spore-production by spreading 

 out their hymenium in shallow tubes attached to a large number 

 of small imbricating pilei instead of by concentrating it in deep 

 tubes attached to one very large pileus. The production of one 

 central branching stipe bearing many pilei, instead of many stipes 

 each bearing one pileus, effects a saving in fruit-body material 

 and in the energy required for penetration through the soil. 



