1915] 



OVERHOLTS STUDIES IN THE POLYPORACEAE 675 



(usually brown) and sharp-pointed, and that distinction is 

 maintained in this paper, although there may be some doubt 

 as to the advantage that accrues from its use. The presence 

 or absence of setae has been made a generic character in some 

 groups of the Basidiomycetes, and even in the Polyporaceae 

 the genus Mucronoporus was founded by Ellis and Everhart 

 on the presence of the setae in the hymenium. The genus 



probably has not received the acceptance that it has deserved 

 at the hands of mycologists. It is difficult to say at times 

 whether a given structure should be designated as a cystidium 

 or not, but the writer is of the opinion that the term should 

 be used in its broadest sense, except that it should not be ap- 

 plied to those structures usually referred to as paraphyses. 

 These latter can usually be distinguished by the frequency of 

 their occurrence as they usually alternate with the basidia, 

 while cystidia or setae are scattered irregularly through the 

 hymenium. In by far the largest number of cases the cystidia 

 are very conspicuous on account of their size, coloration, in- 

 crustation, or other characters. In a few cases the presence 

 or absence of setae is a variable character, in some specimens 

 being abundant and in others very scarce. In such cases the 

 writer has found it advisable to make longitudinal sections 



of the tubes, as the setae are sometimes more abundant in 

 one part of the tubes than in another. A cross-section of the 

 tubes of Fomes igniarius will sometimes fail to show a single 

 seta, but in only one specimen has the writer failed to locate 

 them in longitudinal sections from the hymenium of the same 



plant. They are also almost entirely lacking in some speci- 

 mens of Polyporus dryophilus. 



Basidia. — It is very seldom that the basidia offer char- 

 acters that can be used in separating species. They are al- 

 most universally 4-spored in the Polyporaceae and in those 

 few species where 2- and 3-spored basidia do occur there are 

 always a goodly number of 4-spored ones present also. In a 

 very few cases the basidia are conspicuous on account of their 

 large size. This is true of Trametes Peckii where they are 

 8-10 y. broad, while usually they vary from 3 to 6 y. broad. 



