CHAPTER V.—COMPARATIVE REVIEW.—HYMENOMYCETES, 293 
„ covered by the volva and borne on the broad and stoutly conical stipe-primordium 
(Fig. 135 a). 
At first only the upper surface of the pileus appears distinct and separate from 
the volva; then the commencement ofthe hymenial layer or the lamellae is seen in 
the general shape of a narrow ring beneath the upper surface of the pileus and 
separated from the volva by a layer of tissue, the future body of the pileus (4, c). All the 
principal parts of the structure are now commenced ; the whole tuber has reached 
a size of 10-20 mm., being irregularly ellipsoid in shape and having towards the apex 
a deep depression with thickened and rounded edges, in the middle of which the 
young pileus with the volva 
forms a _ regularly shaped 
cushion-like prominence. All 
these parts are shown succes- 
sively and sharply defined in 
section, most sharply in a me- 
dian longitudinal section, but 
none of them with distinct 
edges bounded by ever so 
small a gap. The definition 
is entirely due to the fact that 
the structure is different in the 
different parts; the young hy- 
menium, the outer surface of 
the pileus, and a strip which 
runs vertically from this into 
the middle of the stipe are 
formed of slender hyphae and 
have little air or none in the 
interstices of the weft; they 
thus have an aqueous trans- 
parence and are contrasted 
with the tissue round them, 
which is white in colour from 



* FIG. 135. Amanita rubescens, Fr. a—d radial longitudinal section through com- 
the presence of broader inter- pound of di ages. S jive stages of development according to 
a . 5 the letters. da small and nearly mature speci: fi secti a 
stices filled with air and has inthe direction ofthe dotted line. ¢ thin jal longktndinal section through the 

inflated hyphal cells among its Pmgunacuinemc Sey cree Delta pete 
narrowly cylindrical elements, Sinn sahen Ce 2 meng and the ren 
If the air is removed the sharp- 
ness of the definition at once disappears. It should be particularly observed 
that the hymenial layer, which received a passing notice above, is seen to be 
separated into the future lamellae from the moment that it first becomes visible ; 
these appear as plates of tissue stretching from the inner surface of the pileus to the 
outer surface of the stipe. Brefeld observed in Amanita muscaria that there was 
never anything more than a narrow space containing air between each pair of plates; 
according to Woronin’s and my own previous investigations, especially into A. 
rubescens, it is shown by tangential longitudinal sections that a narrow plate of air- 
