33« 
THALLOPHYTES. 
the under-side of the pileus ; and from this the radial hymenial lamellae grow downwards 
(///, /), filling up the air-cavity. The hyphas run from the base of the whole fructification 
to the margin of the pileus, forming the outer wall of the air-cavity; the tissue lying in 
the centre elongates into the stalk {IV, st), while the distance from it of the margin of 
the pileus constantly increases ; the hyphse which lie beneath the air-cavity that con- 
tains the lamellae become stretched in consequence, and separate from the stem from 
below upwards, forming a membrane (F, n)), running from the upper part of the stalk 
beneath the lamellae to the margin of the pileus, into which their hyphae are continued. 
When at length the pileus extends horizontally from the elongation of the tissues, the 
membrane (velum) becomes detached 
from its margin, and hangs from the 
stem like a ruffle [annulus). (Compare 
also Fig. 79, p. 96, Boletus ßavidus.) 
The hymenium, as has already been 
mentioned, covers the surface of the 
lamelhformj, peg-shaped, or tubular 
projections of the under-side of the 
pileus. A transverse section of the 
latter across the hymenium gives, in all 
three cases, nearly the same figure, as 
is seen in Fig. 227, drawn from Agaricus 
campestris. A shows a piece of the disc 
of the pileus cut transversely, h the 
substance of the pileus, / the lamellae ; 
in 5 a piece of a lamella is more strongly 
magnified to show the course of the 
hyphae. The substance of the lamella, 
called the Trama (t), consists of rows 
of long cells, which diverge from the 
centre right and left to the outside, 
where the cells of the hyphae are short 
and round, and form the sub-hymenial 
layer {sb in B and C). From these short 
cells spring the club-shaped cells (q), 
densely crowded and at right angles to 
the surface of the lamella, forming 
together the hymenial layer (B, hy). 
Many of these remain sterile, and are 
called Paraphyses, others produce the 
spores and are the Basidia. Each basi- 
dium produces in this species only two, 
in other Hymenomycetes usually four 
spores. The basidium first of all puts 
out as many slender branches (/) as 
there are spores to be formed ; each of these branches swells at the end, the swelling 
increases and becomes a spore {s", which falls from the stalk on which it was 
placed, leaving it behind {s""). 
On the formation of the tissue of this group only one further remark need be made ; 
that in the fructification of some Agaricinae {e.g. Lactarius) some of the much-branched 
hyphae are transformed into laticiferous vessels, from which large quantities of latex flow 
out when they are injured. 
(4) The Gasteromycetes ^ agree with the previous group in the mode of formation 
FIG. 227. — Agnriciis cafnfiestris ; structure of the hymenium; 
slightly magnified ; C a part of B (X 350). The protoplasm is indicated by 
fine dots. 
^ [De Bary, Morphol, und Physiol, d. Pilze, 1866. — Brefeld, Basidiomycetes, p 175.] 
