Homology of the “universal veil” in Agaricus 
17 
occurs as a rudiment in certain species of Agaricus 12 ), among wliich is 
A. campestris. A protoblem may be present in A. arvensis, as suggested 
by the Situation in figs. 6 and 9, bnt as these fruit bodies originated 
underneath the forest mold, the protoblem, if present, was largely removed 
in collecting the plants and preparing them for sectioning. 
The partial, or marginal veil. 
The partial veil, or marginal veil, as it is frequently termed, extends 
from the margin of the pileus to the stem, and when freed from the 
pileus margin forms the ring or annulus on the stem. Fayod 13 ) States 
that it is merely a section of the “universal veil”. If it were entirely 
composed of the tissue external to the gill cavity at the time of the 
origin of the latter it would be merely a section of the blematogen. But 
it is a much more bulky structure. It is very largely composed of tissue 
resulting from growth of the thinwalled hyphae next the stem and by 
growth of hyphae from the margin of the pileus primordium. The latter 
growth forms the upper or inner more compact zone of the annulus, 
while the former gives rise to the looser, open-meshed lower zone. This 
forms a duplex veil or annulus which is so conspicuous a feature of the 
annulus of Agaricus arvensis and some otlier species, the lower looser 
portion usually separating into characteristic patches. It is well shown 
in figs. 5, 6 and 11. There is a section of the blematogen or “universal 
veil”, external to the partial veil, which may remain adherent to the 
margin of the annulus, or be largely sloughed off at a rather early stage. 
But the great bulk of the partial veil is formed by new growth. The 
marginal veil is therefore properly to be regarded as a structure sui 
g e n e r i s. 
Suiiimary. 
1. In the early primordium of Agaricus arvensis , A. campestris 
and A. comtulus, there is an external thick zone of tissue distinguished 
from the internal fundamental tissue, but not separated from it, by a 
more open mesli of interwoven hyphae. The hypha walls of this enve- 
loping zone are thick walled in strong contrast to the thinner walled 
hyphae, richer in protoplasm, of the interior. 
2. The primordia of the principal parts of the fruit body, pileus, 
hymenophore and stem, are endogenous, and are differentiated within the 
central portion. The enveloping zone of loose-meshed tissue witli stout 
hypha walls is the “universal veil”, or blematogen, homologous with a 
similar layer in Amanitopsis vaginata. As Organization of the pileus 
proceeds the surface hyphae of the mature pileus primordium become tied 
to the inner portion of the blematogen layer, so that the latter becomes 
concrete with the surface of the pileus. no cleavage layer being formed 
to separate the blematogen and form the complete or finished “universal 
veil” (the teleoblem) as in the genus Amanita . 
]2) Fries, E., Syst. Myc. 1, 280, 1821. 
13) Fayod. V., Prodrome d’une histoire naturelle des Agar i ein es. 
Ann. Sei. Nat. Bot. VII, 9, 181—411; pls. 6, 7, 1899. 
p 
Myeologisches Centralblatt, Bd. V. " 
