GENERAL [INTRODUCTION 7 



The Gills 



Underneath the pileus the gills are attached in the form of knife- 

 blades collectively called tin- hymenophore. Gravity appears to be 

 responsible for their position <»m the lower side. Rarely one funis an 

 outgrowth of an abnormal character on the top <>r the pileus, some- 

 times in the form of a second mushroom of the same kind with or 

 withoul a stem, sometimes with the ^ills growing upward from ;i 

 small area of the main cap. The latfer case has aever been satisfac 

 torily explained. The .uills arc of course attached all along their 

 thicket- edge i<> the pileus. They may i>e attached to the stem at 

 their inner end. also called the posterior end or base; « >i- they may 

 be free. i. e.. not reaching the stem or at least nut attached. The 

 manner of attachment is shown in Pig. 1. L-6, as adnexed. adnate 



or decurrent. These are important characters for the separation of 

 genera. In some cases all the gills extend from the margin of the 



pileus to the stem, in many, however, they are dimidiate or with 

 very short gills at the margin of the pilens. The spacing of the 

 <;ills is quite important, hut considerable variation occurs in the 

 same species; only relative terms seem usable: crowded, close, sub- 

 distant and distant. The same may he said of their width. 



It is very important to understand their structure. Here a 

 microscope is necessary. A section cut tangentially across the 

 pilens and gills will show a good view of the appearance of the 

 trama, etc., of each lamella. The interior is again composed of 

 hyphae and in such a section they lie either parallel, converging 

 along the median axis, diverging, or interwoven irregularly. In all 

 cases this is the gill-trama and is bordered by the hymenium. 



Tin Hymemwn (See Fig. 2, I.) 



The border which extends over the whole* surface on both sides of 



the uills is the hymenium. "While the hyphae may lie in a general 

 way parallel to the axis of our section, the large club-shaped cells 

 which form the border extend outward at righl angles t<> this axis 

 and form a sort of nap like that of a Brussel's carpet. These large 

 cells are the basidia, (singular, basidi/um), and ai its apex, as -ecu 

 in the figure, each hasidinm hears typically four spores; rarely it 

 may develop only two spores or even three. Bach spore is attached 

 by a minute stalk called the steHgma, (plural, sterigmata). The 

 basidia are in turn continuations of the hyphal filaments which com- 

 pose the trama of the gills. Often there is a slight specialization 



