LYMAN: STUDIES OF HYMENOMYCETES. 
185 
cease to elongate, while the parallel extremities form the tissue of the 
dorsal surface of the pileus (pi. 24, fig. 130). As the fructification 
matures these parallel hypha ends become brownish-walled and agglu¬ 
tinated into bundles which form the scales or squamules of the pileus. 
Similar scales may develop on the stipe. Meantime other branches, 
given off on the ventral side of the growing pileus, turn downward and 
give rise to the tissue of the hymenial region (pi. 24, fig. 130; pi. 25, 
fig. 133), which commences to develop near the stipe and extends 
outward as the pileus grows in diameter. 
By the continued downward growth of certain of the hyphae com¬ 
posing the original hymenial surface, anastomosing ridges and plates 
are formed which enclose irregular areas. From the loosely inter¬ 
woven hyphae composing the plates, branches arise which turn out¬ 
ward perpendicular to the surface, fork cymosely, and form the 
elements of the hymenium. Loosely spreading hyphae, continuous 
with the elements of the trama, radiate outward in all directions from 
the growing edges of the plates, and, meeting those from neighboring 
plates, form the thin flocculent veil which closes the majority of pores 
even in very young fructifications (pi. 24, fig. 131-132; pi. 25, fig. 133). 
These radiating hyphae appear to be largely responsible for the pecu¬ 
liarities in the further development of the spore-chambers. As pre¬ 
cursors of the advancing trama, they may, by becoming massed, 
divert the growth to one side or another, thus causing the trama to 
vary in width, to divide, to form a bridge or septum across the spore 
chamber, etc. (pi. 24, fig. 131-132). The basidia originate directly 
from the elements of the trama on cymosely-branched hyphae without 
the formation of a definite subhymenial layer. Apparently any of the 
elements of the trama may produce basidia in favorable locations, 
hence an extension of the trama in any direction becomes promptly 
covered by a hymenium. Where the thickening of the veil has thus 
led to the closing in of a spore chamber, a new hymenium may develop 
outside this septum, thus beginning the formation of a new spore 
chamber which is at first freely open to the exterior as a shallow depres¬ 
sion, but which rapidly deepens by the growth of its walls and becomes 
hidden by the development of the veil as in the case of the original 
chamber. As the fructification approaches full development, the 
downward growth of the plates ceases and the veil increases in thick¬ 
ness until the mouths of most of the spore chambers are nearly or quite 
concealed from view. 
