THE DEVELOPMENT OF SOME SPECIES OF AGARICS 23 1 
end and a portion of the peripheral hyphae stain deeply, which indi- 
cates an area of active growth. 
This fundamental tissue is soon differentiated by growth direction 
of the apical threads as stipe primordium. At this time the inner 
structure of the stipe fundament is a woof of slender homogeneous 
hyphae, while some of the hyphal threads near the surface of the stipe, 
growing more rapidly than the other elements, extend outward and 
form a loose floccose layer. Figure 49, a median longitudinal section, 
shows this layer as a narrow zone which stains more deeply. This 
structure is composed of the dead ends of those hyphae which extend 
beyond the immediate surface of the stipe and is very ephemeral. 
Pileus Primordium.- — The origin and development of the pileus 
fundament agrees with the preceding species. The elements extend 
outward in all directions with a slight tendency to epinasty. In this 
species the fundament consists of a peripheral zone of long radiating 
hyphae and a dark staining central portion. The hyphae of both 
the loose and the more dense regions have the same origin; i. e., the 
elements of both regions are the result of radial diverging growth from 
the stipe fundament. 
Further development of the pileus is by the continued radial 
growth of the hyphae. At the margin by epinastic growth the hyphae 
curve downward, forming the annular groove (Figs. 50, 51). In the 
stages represented by Figures 52-54, the hyphae branch profusely 
and are organized in a very compact structure, except a very thin, 
loose surface zone. The pileus margin develops by centrifugal growth. 
On the surface of the annular groove in the angle between the pileus 
and stipe the hymenophore fundament is organized. 
In a later stage of development, represented by Figure 55, the 
pileus margin is so strongly involute that the edge is curved upward 
against the lamellae. The marginal hyphae span the intervening 
space between the pileus margin and the gills. At this stage of growth 
these hyphae function as a marginal veil, though this veil is very 
different in origin from the marginal veil of those species with endog- 
enous origin of the hymenophore. They do not, at any stage of 
development which I have examined, interlace with the hyphae of the 
stipe, as Hartig suggested for Armillaria mellea (12). Such an inter- 
lacing might occur in case the margin curved down against the stipe 
below the hymenophore area. In all the specimens examined, how- 
ever, the pileus margin curves up toward the hymenophore. Hypo- 
