1915] 



OVERHOLTS — STUDIES IN THE POLYPORACEAE 671 



were investigated and the results not as satisfactory as could 

 be desired. 



It is a significant fact, however, that no attempt has been 

 made to classify the Polyporaceae on the basis of spore or 

 other hymenial characters, although it is recognized that, out- 

 side of the algae, the organs concerned in reproduction are 

 usually subject to less variation than are external morpho- 

 logical characters. That no such attempt has been made is 

 due to two causes : first, the dislike on the part of students of 

 the careful and painstaking observations that must often be 

 made to determine those characters ; and second, to the wide- 

 spread belief that the pore fungi are spore-bearing only for 

 a short interval of time during the year, and that they must 

 be examined at the right moment or the spores will have dis- 

 appeared. When it has been shown that the second objection 

 is invalid and that hymenial characters are usually not hard 

 to make out, the first objection will largely disappear. 



In the course of the last year the writer has spent a con- 

 siderable portion of his time in searching for these char- 

 acters, not only in the Polyporaceae but in other related 

 families as well. The methods employed are given on a fol- 

 lowing page, and suffice it to say here that probably 75 per 

 cent of the collections examined contained spores, and a large 

 percentage afforded other microscopic characters that played 

 a considerable part in distinguishing one species from another. 

 The characters that may be obtained by the use of the micro- 

 scope are here enumerated and some indication given as to 

 their possible value. 



Discussion op Microscopic Characters Now Available for 



Use as Generic and Specific Characters 



The characters that may be obtained by the methods out- 

 lined on a following page are as follows: spore characters, 

 presence or absence of cystidia, setae and other sterile organs 

 in the hymenium, basidial characters, hyphal characters, and 

 the presence or absence of sterile structures in the sub- 

 hymenial tissue. 



