212 BOTANICAL GAZETTE [SEPTEMBER 
the ground tissue left in the angle between the stem and hymeno- 
phore. This tissue increases, both by interstitial growth and by 
the addition of hyphae which grow down from the pileus margin 
(fig. 22). By the time that the gills are well formed this tissue 
occupies a considerable area lying between the margin of the pileus 
and the surface of the stem, and forming the floor of the gill cavity. 
It is covered externally by the blematogen, with the inner surface _ 
of which its hyphae are interlaced, as some of them are with the stem 
surface. .When expansion of the pileus occurs and the veil is 
ruptured, it is left upon the stem as an annulate membrane com- 
posed of two layers, the coarse, scaly blematogen layer below and 
the partial veil above. 
ORIGIN AND DEVELOPMENT OF LAMELLAE.—In a recent publica- 
tion ATKINSON (9) has shown that in the Agaricaceae thus far 
studied there are two types in regard to the origin and development 
of the lamellae. First, the ‘‘Agaricus” type, in which the gills 
arise by downward growing radial salients of the hymenophore, 
accompanied or preceded by a more or less well developed annular 
prelamellar cavity. Second, the “(Amanita’’ type, in which there 
_is no general annular prelamellar cavity, and the origin of the 
Tasman he Selo eeting Sore thy es 
ment to the stem, and attached to siege P. sores obviously 
se es he 
: belongs tO the first type 
: that in the course of development of ie jeune bak tas see oy 
annular, prelamellar cavity, though weak, and a palisade layer are 
fo 
eo. 
‘The origin and differentiation of the gills from the hymenophore _ 
e sea a ee 
