THE DEVELOPMENT OF SOME SPECIES OF AGARICS 
transverse section through the stipe and pileus, shows the primary 
lamellae as "bars" extending between the pileus and the stipe. Be- 
tween the ''bars" on the morphological under surface of the pileus, 
down-growing salients of the secondary gills are shown. They develop 
and progress radially, as do the primary lamellae. Figure 6i is a 
slightly oblique transection through the margin of the pileus and upper 
portion of the stipe and shows the increase in number of lamellae on 
the pileus margin as compared to the number of primary gills on the 
stipe. 
Further Growth of Pileus and Stipe. — The pileus elements in the 
more mature stage have in general a radial, horizontal direction. 
The trama of the pileus increases by branching and elongation of its 
elements. The size of the stipe increases likewise by branching and 
interstitial growth. The lengthening or elongation of the stem, as in 
the previous species studied, is the result of the extension in length, 
of the cellular elements. 
Summary 
1. The young basidiocarp and stipe primordium consist of a homo- 
geneous weft of slender, terete, interlacing hyphae. The general 
growth direction of the elements is parallel with the axis of the young 
fruit body. The hyphae converge at the apex. The cellular elements 
are comparatively short, cylindrical cells, rich in protoplasmic content. 
2. The pileus primordium is differentiated by the divergence of 
the apical hyphae which grow upward and laterally. This divergence 
serves to mark the origin of the pileus and differentiates it from the 
stipe fundament. 
Further differentiation of the pileus is the result of continued 
growth of the primordial tissue. By profuse branching and intersti- 
tial growth of the elements, an intricately interwoven tissue is pro- 
duced. At the same time the lateral hyphae by epinastic growth 
bend downward, forming the annular groove. 
3. The primordium of the hymenophore is organized simultane- 
ously with the origin of the pileus margin. The first differentiation 
of this tissue is on the surface of the annular groove in the angle be- 
tween the pileus and stipe. This annular layer progresses centrif- 
ugally. 
4. By continual branching of the hyphae, the hymenophore primor- 
dium changes to a definite layer of parallel threads, perpendicular to 
