14 
GEORGE F. ATKINSON 
case in Fayod's angiocarpous type (1. c, p. 286), nor is released by 
the gelatinization of an intermediate zone as in the Amanitae, it may 
have no very great taxonomic significance. It is fundamental tissue 
of limited extent, the outer layers are often gradually and irregularly 
broken down and partly exfoliated as the plant matures. Where it is 
quite distinct at maturity there occurs considerable increase of its 
elements during early stages of growth. An inner zone, or in some 
cases perhaps nearly all of it, remains in coalescence with the undif- 
ferentiated surface of the pileus. But when it is of the character 
presented by Agaricus arvensis (figures 1-4) and comtulus (figures 7 and 
10), consisting of thick- walled hyphae, further growth of its elements 
is probably not extensive. In such cases the outer portion is sloughed 
off or exfoliated as shown in figures 5, 6 and 9, leaving the surface of 
the young pileus more or less eroded for a time from an irregular 
cleavage plane through the zone of the universal veil. 
Since no definite boundary between the universal veil and pileus 
can be found in these examples, it appears to me, that, in the genus 
Agaricus, the external fundamental tissue below the pileus fundament 
is not always separated from the fundament of the partial veil, but 
gradually passes over into it, so that the partial veil really has a duplex 
structure at a very early stage, different from the duplex condition 
which appears later due to growth from the margin of the pileus and 
from the surface of the stem. The innermost portion of it is continuous 
with the margin of the pileus tissue from a very early stage. Further 
development of this fundamental tissue, forming the marginal veil, 
takes place after its separation from the stem primordium by the 
annular gill cavity. The inner portion of it is also increased by con- 
tinuation of the growth of threads from the margin of the pileus which 
seems to indicate rather clearly that the marginal or partial veil is not 
wholly made up of a section of the universal veil. 
The "universal veil," or blematogen layer, then, in the species of 
Agaricus thus far studied by myself, one might say consists of a poorly 
defined external zone of fundamental tissue, not clearly differentiated 
even after the organization of the pileus, so that the inner portion is 
more or less concrete with the pileus and marginal veil, while the outer 
portion may entirely disappear or remain as loose fragments or delicate 
scales on the surface of the pileus, forming in some cases a slight 
external contingent of the marginal veil. 
Where the external free contingent of the primary universal veil, 
