THE DEVELOPMENT OF CORTINARIUS PHOLIDEUS 52 1 
the young fruit-bodies of this species are the numerous interhyphal 
spaces scattered throughout the basidiocarp. 
Differentiation of the Stem Fundament 
Very early in the development of the fruit-body the hyphae in the 
basal part increase in number and show evidence of more rapid growth, 
so that this portion of the basidiocarp becomes more dense in struc- 
ture. This new growth is the primordium of the stipe, which, by 
progressive growth and differentiation, finally reaches the apex of the 
fruit-body. From the beginning, the structure of the basidiocarp is 
compact, and the gradual progressive differentiation of the stem 
fundament does not at first produce any marked change in appearance. 
In figure 2 the fundament is well differentiated nearly to the stem 
apex; the latter is still in the primordial condition. In figure 3 at the 
left is shown the compact cortex of the stem fundament, from which 
the looser hyphae of the inner portion of the blematogen radiate out- 
ward and upward. The cortex of the stem fundament is somewhat 
more dense and deeply staining than the inner portion, as shown in 
figure 5. 
A similar, but more marked origin of the stem, has been shown to 
occur in two species of Lepiota (6), in Rozites gongylophora (11), in 
the three species of Pholiota already mentioned, and in five species of 
Cortinarius (8). 
Differentiation of the Primordia of Pileus and Hymenophore 
After the organization of the stem fundament the hyphae in its 
apical end take on more rapid growth and branch freely, as indicated 
by their deeper stain and by the fact that they traverse the interhyphal 
spaces at this time. This new interstitial growth causes a bulbous 
expansion of the stem apex, which marks the young primordium of 
the pileus (fig. 6). At the same time the peripheral hyphae of this 
apical region, instead of growing, in general, straight upward, as 
they have done heretofore during the development of the stem 
fundament, now grow outward in all directions (fig. 7). On the lateral 
surfaces they become subject to epinastic influence and turn strongly 
downward, forming the pileus margin, as shown in figure 8 by the 
small deeply stained area on either side of the pileus, beneath the 
blematogen layer. 
