1917] SAWYER—PHOLIOTA 211 
pileus margin at this time is turned downward and often somewhat 
incurved as a result of epinastic growth, and lies nearly parallel 
with the surface of the stem, which still slopes outward at a slight 
angle (fig. 10). 
FORMATION OF ANNULAR PRELAMELLAR CAVITY.—During dif- 
ferentiation of the young basidiocarp some ground tissue is left 
below the hymenophore primordium in the angle formed by the 
junction of the stem and pileus fundaments. In later development 
this ground tissue increases to some extent by interstitial growth, 
but the more rapid growth of the stem, hymenophore, and pileus 
subjects it to tension, and it very early becomes loose in texture 
(fig. 4). As the stem elongates and the pileus broadens out, this 
tension is further increased, so that the ground tissue becomes still 
looser, with large spaces between the hyphae. At first it only 
partially tears away from the surface of the hymenophore, and as a 
result the gill cavity thus formed is weak, with strands of ground 
tissue traversing it (figs. 13, 14, 16-20). The strength of the pre- 
cavity varies in different individuals, as has been shown 
to be the case in Agaricus rodmani (8); but in any case, in later 
stages, but long before the gills are exposed by rupture of the 
veil, the strands of ground tissue become completely broken away, __ 
and the edges of the lamellae are entirely free within the bl ae 
cavity. ; 
ORGANIZATION OF PARTIAL VEIL. the terms hleniati or 
gen’ 
“universal veil” and “marginal” or “partial veil” have been 
interpreted by ATKINSON (5), and are used in the same sense here. 
The formation of the blematogen has already been described. oe 
radial growth of hyphae in the apex of the young fruit body is very ae 
___ Tapid for a time, and a thick layer is formed, enveloping the entire = 
| Plant, but it is more dense i in the rupee region (Ges ro. ~~ . 
- become i ps pero ‘Because = corns 
: — Ast universal veil b mes subject to tet 
