Overholts : Diagnoses of American Porias 9 



In cross sections of the hymenium the trama is seen to be very 

 compact, the sections of the closely crowded, thick-walled hyphae 

 giving a pseudo-cellular appearance (PL I, fig. 2), such as is 

 always found in similar sections of the hymenium of Fomes con- 

 natus, a common perennial sessile form on species of Acer. More- 

 over, Bresadola, the author of this species, states that it has often 

 been confused with the resupinate form of F. connatus (=F. 



Fig. 5. P. nigrescens. a, Lateral view of vertical section through spo- 

 rophore, showing the evident, separating annual layers ; b, Surface view show- 

 ing the failure of growth of current season to cover the entire growth of 

 the previous year. X i. 



populinus) . This pseudo-parenchymatous appearance is also pres- 

 ent in the hymenium of Polyp or us- rigidus Lev. as interpreted by 

 the writer, which species is also often entirely resupinate, has a 

 flesh-colored hymenium when fresh, the spores being similar. 

 However, that species does not become noticeably darker on dry- 

 ing, nor is it ever perennial. In the present species the hymenium 

 in some collections is now quite blackish or smoke-colored. 



The identity of American collections rests in part on the opinion 

 of Rev. Bresadola, its author, who so referred specimens of one 

 of the collections cited above. In addition he has very kindly 

 communicated to the writer a small portion of co-type material 

 which has been carefully examined and with which the writer's 

 specimens agree quite fully. The original description says " sporis 

 non visis," and, curiously enough, they are rarely found in dried 

 American specimens, but have been found abundantly in fresh 

 material. In the co-type material they are absent from the appar- 



