226 
A. W. BLIZZARD 
Clitocybe adirondackensis Peck 
Basidiocarp Primordium. — The undifferentiated basidiocarps of 
this species are long, slender bodies, tapering toward the apex. They 
are usually curved or bent in various directions. Those studied 
measure 6om in diameter and I mm. to 2 mm. in length. The hyphae 
are very slender, wavy threads, averaging i.^ix in diameter. They 
run in a longitudinal direction (Figs. 31 and 41). The central hyphae 
extend to the apex where they converge into a blunt point. The periph- 
eral ones end in such a manner as to form a slanting surface from 
the base to the apex. There is no differentiation at this time, the 
whole fruit body staining homogeneously. 
Pileus Primordium. — When the young primordium of the fruit 
body reaches a diameter of about 300M the lateral threads at the apical 
end begin to spread laterally (Figs. 32 and 42). The central hyphae 
continue their growth upward. The interhyphal spaces are filled by 
new elements which are produced by branching of the older hyphae. 
This structure is the pileus primordium, and, as in Omphalia chryso- 
phylla, the divergence of the threads indicates the differentiation of 
the pileus fundament at the apex. 
Further differentiation of the pileus is the result of continued 
growth of this primordial tissue. Around the upper lateral surface 
of the stipe primordium and on the under side of the young pileus, 
the ends of the diverging hyphae stain deeply and mark the origin of 
the hymenophore fundament (Fig. 33). The central apical hyphae 
continue their growth upward and by profuse branching add materially 
to the thickness of the pileus, while the intermediate elements bend 
gently outward. 
By continued branching and interstitial growth of its elements 
the pileus increases in diameter. At the same time the central hyphae, 
as compared with those of the periphery, elongate less rapidly. Thus 
the intermediate and peripheral threads, growing upward and outward 
at an oblique angle of about 45°, cause the pileus to become plane on 
its upper surface (Fig. 35). The marginal hyphae at the same time 
continue to curve abruptly downward. In this way a shallow and 
very narrow annular groove is formed. 
In later stages in the under portion of the pileus next the stem, 
hyponasty replaces epinasty. The form of the pileus consequently 
changes from plane to umbilicate, and then to infundibuliform, while 
