104 
wards to form the trama of the gills. In the formation of these gills the cellular 
filaments or hyphe take yet another direction—the fourth since they commenced 
to form the juvenile plant—in a horizontal line, when they immediately begin to 
discharge their most important function, that is, producing the hymenium or 
spore-bearing surface. Before doing this, however, they undergo a differentiation 
which is well worthy of study. The cells, of which they are made up, become much 
shorter, indeed, almost globular or polygonal, and constitute the sub-hymenial 
tissue, which is an extremely thin layer, not unlike the succulent parenchyma of 
flowering plants, except being devoid of chlorophyll. From the outer cells of this 
tissue are produced club-shaped cells, mostly placed horizontally, and closely — 
pressed against each other, forming the hymenial layer. Some of these club-shaped 
cells remain sterile, while others become basidia, whose work is to produce the re- 
productive bodies or spores. This they do by throwing out at their summits two 
short slender spicules, on the ends of which are produced the spores, which, when 
ripe, drop off and in due time germinate, and so commence again the cycle of life 
I have described. What holds good in the common mushroom, holds good, with 
some slight differences in most of the higher Hymenomycetes, and it will be evident 
from this brief sketch, that we have a class of plants before us, composed, for the most 
part, of a rapidly-growing, soft, filamentous tissue, easily turned out of its direction 
of growth by any more resisting substance, but capable of reuniting again with 
great facility when the obstacle is passed; hence we often find grass stems, bran- 
ches of shrubs, and other objects holding their position, in the flesh of the stem 
or pileus of Agarici, Polupori, Hydnei, &e., or causing a separation at times where 
union is afterwards impossible, thus giving rise to deformed specimens. The 
character of the tissue lends itself also to the formation of unions by adhesion, so 
exceedingly common, such as where two individuals of the same species become 
joined in their stems, either partially or throughout their entire length, or in their 
pilei while their stems are separate, or in their stems and pilei at the same time. 
These unions become so perfect,—that is, the cellular tissue is so intimately inter- 
woven,—that the line of union cannot be detected even by the microscope, and can 
only be inferred from a depression according with the line of juncture. This has 
been noticed in Agaricus vrocerus (t. fig. 1), A. campestris (fig. 2), Lactarius seri- 
fluus (fig. 3), Russula alutacea (fig. 4), and many others.” 
‘*A much more curious fact, attributed to adhesion, is that of an Agaric 
bearing on the top of its pileus one or more pilei of the same species in a reversed 
position—that is with the gills uppermost—sometimes without a stem, at others 
with one (figs. 5, 12). This has been observed in Agaricus phyllophilus (fig. 5), A. 
campestris (figs. 6,12), A. fascicularis (fig. 7), A. fimicoia (fig. 8), Russula vitellina 
(fig. 9), R. nigricans (fig. 10), and R. fragilis (fig. 11), and doubtless in many other 
species not recorded. It has been accounted for in the following manner :—In a 
group of young plants two or more have been so situated, owing to the inequalities 
of the surface on which they were growing, that their pilei have adhered together, 
and the most vigorous has lifted the others from their attachment, and continued 
its growth with these captive pilei on its head. In the example of Agaricus phyl- 
lophilus sent me by Mr. Plowright, there are no less than eight reversed pilei 
