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GERTRUDE E. DOUGLAS 
15 14 15 16 
quite conspicuous even to the naked eye. As the plant matures, new 
elements appear to be formed at the margin of the pileus. These 
extend across, below the gill cavity, to the stem. Whether or not 
the cortina has its insertion on the upper surface of the pileus margin, 
depends, therefore, on our conception of what the cortina is. C. 
anjractus is placed by systematists in the sub-genus, Phlegmacium, 
one of whose characters is the presence of a partial veil only. We have 
seen from this study, however, that C. anfractus does possess a blemato- 
gen outer layer, which is homologous with a universal veil, but is not 
clearly differentiated from the pileus as such. The marginal or partial 
veil, strictly speaking, consists only of the ground tissue, between the 
stem and pileus margin and the new elements added by growth. As 
the term cortina is a special one, applied chiefly to the cobwebby veil 
of this genus, it should probably include all 
the fibers of the veil and thus may be con- 
sidered as consisting of both blematogen and 
partial veil tissue. 
Origin of the Lamellae. — The first evidence 
of gill formation occurs in specimens of about 
3.5 mm. diameter. Figures 12-16 show a 
series of longitudinal sections, cut parallel 
with the axis of the stem, in the positions 
represented by the corresponding numbers in 
the diagram of text-figure i. Let us first 
examine section 14, from a plane through 
the center of the gill cavity, recalling, as we 
do so, that the hymenophore always de- 
velops centrifugally and in consequence, the 
oldest stages will be nearer the stem and 
the youngest nearer the margin of the pileus. 
The latter portion of the hymenophore is 
still in the primordial state (fig. 16) showing 
the irregular, sharply pointed hyphae. As 
we approach the stem, we pass by even pali- 
sade tissue to the young gill salients (fig. 
15) growing down into a now well defined 
annular cavity. If we examine them in greater detail (fig. 18), we see 
that they are formed by the dense crowding of the palisade layer, 
accompanied by an elongation of the subadjacent hyphae in regularly 
Text-fig. I. Diagram to 
show plane of sections 
shown in figures 12-16, 
plate IX. 
