1915] 



OVERHOLTS — STUDIES IN THE POLYPORACEAE 691 



margin is not crisped, sterile, and thin, that the pubescence 

 of the pileus is not nearly so prominent, and that the context 

 is soft and floccose. The type specimens are not densely im- 

 bricate as in P. crispus but more nearly approach the condi- 

 tion found in P. adustus. 



The microscopic characters of these three species are 

 identical and do not afford additional means of separating 

 them. The tramal tissue of the pores is decidedly brown in 

 color, the hyphae are small, and a large percentage of them 

 are cut transversely in a cross-section of the hymenium. The 

 spores in all three species are oblong or oblong-ellipsoid, and 

 measure 3.5-4.5 X 1.5-2.5 /*. There are no cystidia or other 

 sterile bodies in the hymenium. 



In endeavoring to find characters on which to separate the 

 three above-named species (and especially P. adustus) from 

 specimens heretofore referred to P. fumosus and P. fragrans, 

 recourse was had to microscopic sections of the hymenium. It 

 was at once apparent that when longitudinal sections were 

 prepared, according to directions given on page 678 of this 

 paper, the tramal tissue of the tubes of P. adustus, P. crispus, 

 and P. Burtii were decidedly brown in color, while those of P. 

 fumosus and P. fragrans were entirely hyaline, except for the 

 eosin stain. This character has been tested out thoroughly 

 and is believed to be a satisfactory and constant one on which 

 to differentiate these two groups of species. By obscuring the 

 labels on the slides containing the sections of the different 

 species it was found possible to easily separate the sections of 

 the species of the one group from those of the other group by 

 this character, and then verify the separation by uncovering 

 the labels. Since suitable sections can be readily prepared in 

 a very few minutes, the task of deciding between the two 

 groups is an easy one when they cannot be readily separated 

 on the general appearance of the specimens. Some such 

 method of procedure is especially desirable in separating P. 

 adustus from P. fumosus, since thin or young specimens of 

 the latter are easily confused with the former species. How- 

 ever, care must be taken not to confuse the dark color some- 

 times obtained in thick sections of P. fumosus with the truly 



