42 
GERTRUDE E. DOUGLAS 
continue to increase, the subadjacent tissue next the stem begins to 
extend downward in radial Hues carrying the hymenophore primordium 
with it (figs. 28, 29 and 44). Gradually the palisade layer becomes 
more even (figs. 30-34, 47). By centrifugal growth the gill folds 
progress toward the margin of the pileus, where new primordial tissue 
is being organized (fig. 34). As in the case of Mycena subalcalina, the 
pressure of growth in the hymenophore region causes a loosening of 
the subadjacent tissue (figs. 29, 32, 47). More advanced stages in 
the development of the gills are shown in the fruit bodies represented 
in figures 35-39 and 40-42. As the gill ridges continue to grow, 
they become very broad with large spaces between. They finally 
assume the more or less triangular shape in cross section, which is 
one of the distinguishing characteristics of the genus Hygrophorus 
(figs. 41, 42). The trama, as can be seen in figure 40 in surface 
section and in figure 41 in cross section, is similar in character to that 
of the pileus. 
The palisade layer, when finally organized, may be studied in 
photographs of figures 41, 45, 46. It shows especially well on the 
older part of the gills nearest the pileus. The ends of the hyphae 
have become very crowded and blunt, thus bringing about an even 
surface on the gill. No nuclei are present in the extremities but they 
are very conspicuous and deeply stained at the bases of the palisade 
layer cells. The adjacent tissue contains very abundant and deeply 
stained nuclei and presents much the same appearance as it did in 
species of Cortinarius (15). Just above this is the loose open zone 
which extends into the gills and into the pileus region between them, 
subadjacent to the hymenophore, and which gives rise by branching 
to the hyphal elements which make up the hymenophore. The 
palisade layer is not as compact (fig. 41), the hyphae have become 
clavate and the nuclei have migrated into the tips. These hyphal 
ends are apparently young basidia in the process of forming. 
Structure of the Stem and Pileus. — The cap does not separate easily 
from the stem in mature stages, a fact which is due to the homogeneous 
character of the tissues of pileus and stem in gymnocarpous forms. 
It is made up of the continuation of the hyphae of the stem, as we ob- 
served in Mycena subalcalina. At the surface no blematogen is present 
and there is practically no change in the character of the tissue. The 
ends of the hyphae grow somewhat unevenly, so that the surface is 
at first irregular (fig. 28). Later on the ends become swollen and 
are cut off by cross walls (fig. 43). 
