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A. W. BLIZZARD 
nastic growth of the older portion of the pileus begins soon, causing it 
to expand, thus Hfting the margin up and outward far away from con- 
tact with the hymenophore. The growth of the pileus in thickness is 
primarily the result of the enlargement of its elements accompanied 
by branching and intertwining of the threads. 
Hymenophore Primordium. — Soon after the origin of the pileus 
primordium, the ends of the peripheral hyphae which are perpendicular 
to the surface of the annular groove, are rich in protoplasm and stain 
deeply. This is the region of the hymenophore primordium. This 
region, as in Omphalia chrysophylla and Clitocyhe adirondackensis , 
develops centrifugally and adds new elements by intercalary growth. 
Palisade Layer. — By continued introduction of new elements, 
this layer becomes compact and the free ends reach the same level 
(Fig. 66). The increase in size of the cellular elements and the ex- 
tending downward of the subadjacent hyphae produce regularly 
spaced, radial folds in the palisade layer (Figs. 57, 58). These folds 
are the salients of the primary lamellae and appear first on the stipe 
very near the angle between the latter and the under surface of the 
pileus. Thus, the gills are decurrent from their very first appearance. 
At this period of development the hymenophore layer on the under 
surface of the pileus is in the level palisade stage, near the stipe (Fig. 
56). It gradually grades off into the primordial condition at the mar- 
gin. Therefore, since the gills follow the same centrifugal succession 
as did the structures preceding their origin, the salients continue their 
development toward the margin of the pileus. Thus, Figure 58 (a 
little later stage than Fig. 57) shows their first appearance on the 
under surface of the pileus. 
Further growth in width of the lamellae is brought about by 
growth of the tramal hyphae in these folds. This growth aids in 
pushing the palisade layer outward at the edge of the salient. By 
corymbose branching new elements are introduced into the palisade 
layer by intercalary growth. The hyphae that grow down into the 
lamellae from the trama of the pileus form the trama of the gills. 
Figures 67-69 show a serial development of a gill from the origin of 
the salient to a lamella fairly well along in growth. 
Origin and Development of Secondary Lamellae. — As the primary 
gills advance from the stipe to the margin of the pileus, they diverge 
from each other. In the spaces so produced on the under surface of 
the pileus near the stipe, the secondary lamellae arise. Figure 59, a 
