A STUDY OF DEVELOPMENT IN THE GENUS CORTINARIUS 327 
the development of the palisade layer (figs. 27, 28, 29, 30, 31). Owing 
to the weakness of the fibers of the ground tissue, a strong gill cavity 
makes its appearance early (figs. 29, 30). In figures 32-38 is shown a 
series of sections of the earliest fruit body to show the gill beginnings. 
Excepting for slightly more irregularity of the salients, their develop- 
ment is quite similar to that of C. anfractus. In this specimen the 
gills are merely adnate to the stem and, in consequence, do not show 
the pockets at the junction of the stem, which we saw in C. anfractus. 
There is considerable variation in this respect among individuals of 
the same species. The older specimen, shown in figures 39-43, has 
decurrent gills and in consequence we find the pockets present. This 
series of sections is interesting on account of the beginning of the 
secondary gills. The primary ones have already reached a consider- 
able degree of development, when the second series begin to appear 
(figs. 45-49). As the pileus expands, the primary salients are pushed 
farther and farther apart by the intercalary growth and finally the 
new salients begin to form. At first the surface between the original 
gills is even. Then the ends of the hyphae become swollen and there 
is considerable crowding, especially next the primary gills (fig. 45). 
This is followed by an elongation of the hyphae, carrying the gill 
down into the cavity. The hyphae in the central portion grow 
straight downward, but their dense crowding and swollen ends cause 
the others to turn outward. In the course of development, many new 
hyphae are interpolated between the old, contributing also to the 
increase in length. The terminal cells of the hyphae take the stain 
with difficulty, showing that the greater activity in growth is behind 
the tips, where the stain is deep and the nuclei abundant. We find in 
this species the same narrow deeply staining growth region sub- 
adjacent to the salients and extending down into their trama (figs. 
40-43, 48, 49), that we found in C. anfractus. Figure 43 may need a 
word of explanation. The section was cut somewhat obliquely, so 
that it passes through the gill cavity on one side, but through the 
margin of the pileus on the other. It thus passes perpendicularly to 
the direction of growth of the gill salients on one side, thereby forming 
pockets as on the stem. This results from the strongly incurved 
margin of the pileus (see figs. 40-42). In figure 50 is represented a 
section of the hymenophore from a fruit body having mature gills. 
