20 
GEORGE F. ATKINSON 
8. External to the pileus primordium and the upper portion of the 
stem fundament is a zone of fundamental tissue with an open mesh. 
The hyphae in general have a strong radial direction but are clearly 
interwoven into an open-meshed plectenchyma. The surface is not 
marked by free ends, but by tangentially lying threads forming part 
of the weft. The outer portion of this represents the ''universal 
veil," or blematogen layer. 
9. The later stages of development are in general as in Ag. arvensis, 
but the partial veil, while presenting the same general duplex char- 
acter, is not so strongly developed. 
10. In all three species of Agaricus, which I have studied, there is 
an external zone of fundamental tissue. The outer portion of this, 
not well defined, does not pass over into, or give place to, the cuticle 
proper of the pileus, nor the partial veil. This not well defined outer 
zone of fundamental tissue represents the "universal veil," or blema- 
togen. An outer portion of the "universal veil" usually becomes torn 
free because of a lagging or cessation of growth. It may form delicate 
scales on the pileus, or disappear earlier. An inner portion of the 
universal veil, variable in amount, remains concrete with the cuticle 
of the pileus. A small portion in a very young stage lies external to 
the partial veil and is connected with its outer surface in the young 
stage. But the great increase in the partial veil, by additions from 
the margin of the pileus and by growth of the portion next the stem, 
indicate that the "universal veil" probably plays an insignificant part 
in the formation of the partial veil, which is a distinct structure. 
11. The "universal veil" as interpreted here, is homologous with 
the undifferentiated "universal veil" in Amanitopsis vaginata. Since 
this zone gives rise, in a later stage of development, to the mature 
universal veil, or volva, in the Amanitae, it may be called a blematogen 
layer, or blematogen. 
12. In AgaricMS campestris, under certain conditions, particularly 
those of culture, there is often manifest an additional universal veil of 
delicate floccose character, easily separated from the young carpophore, 
which in age is found as small white floccose patches on the surface of 
the pileus. This may be called the primary universal veil, or, to be 
more exact, the protoblema or protoblem. When present it is external 
to the blematogen layer which, in the species of Agaricus studied 
here, is never differentiated into a distinct universal veil, or volva, = 
the teleoblema. 
