6 



aIycologia 



the plant does not separate readily from the substratum and old 

 specimens are entirely inseparable. But collections have been 

 noted in which the young growing- specimens on a smooth surface 

 peel off in strips. 



Fig. 3. P. ferruginosa. a, Specimen from Washington, on Acer (3879) ; 

 b, Specimen from New Hampshire, on Fagus (5096). X 1. 



When growing on an uneven surface or in a very oblique position 

 the hymenium may be quite uneven and nodulose or thrown into 

 distinct undulations. An extreme case of this unevenness is seen 

 in specimens collected in Canada by Macoun and made the basis 

 of a new species, P. macouni, by Peck. In these the plants were 

 growing over old mosses. Otherwise they are typical P. fer- 

 ruginosa. 



Usually the species is annual or at least most of the collections 

 examined are of the annual type. The greatest departure from 

 this condition that has come under observation is in specimens on 

 Acer from Washington, collected by W^eir. In these, four layers 

 of tubes are present. When cut with a sharp knife and examined 

 under a lens these layers of tubes are fairly distinct, but to the 

 naked eye they are not sharply separated. The hymenial surface 

 of old weathered specimens occasionally fades out to gray. 



The affinities of the species are with P. viticola Schw., for which 

 a better name is probably P. (Trametes) tenuis Karst. From 

 this species it is distinct in the spores, which there are cylindric 



