Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 5: Supplementary Volume
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit36060/296/
226 REPRODUCTION, VEGETABLE (Vegetable Ovum). 
sistence and of a dark-brown colour ; the other 
white and opaque. The former, which cor- 
Fig. 145. 
(A 
Section of part of the receptacle of a Truffle, about 
250 diam. 
a, outer layer of the peridium consisting of a 
resistant tissue of thick-walled cells ; b, inner layer 
of the same, formed of filamentous tissue continu¬ 
ous with that of v, one of the venæ intemæ, or par¬ 
titions by which the compartments (originally 
cavities) of the truffie are bounded. Portions of 
two- of these compartments are seen with the thecæ 
and septate filaments which they contain. 
responds to the partitions which, in the young 
state of the truffle, separated the cavities, is 
continuous with the external tissue which 
composes the envelope or peridium, and con¬ 
stitutes the vena internæ of Vittadini.* The 
laminae which it forms, consist of filaments 
running, for the most part, parallel to each 
other. The white substance which occupies 
the original cavities of the tuber, is formed 
of closed tubes, which are given off in great 
numbers from the surfaces of the laminae. 
These tubes, which are the terminations of 
the filaments of which the laminae are com¬ 
posed, are of two kinds. Some are of equal 
diameter throughout, and divided at intervals 
by septa ; others, much shorter, are dilated at 
their extremities, and contain spores (thecae). 
Each theca is an obovate vesicle, and con¬ 
tains two, three, or more spores, never more 
than eight. Each spore is invested with a beau¬ 
tifully reticulate, or sometimes warty epispore, 
within which may be distinguished a smooth 
inner membrane, immediately enclosing the 
oleaginous contents.-)- 
* Vittadini, Monog. Tuberacearum, p. 2. et seq. 
f L. It. & C. Tulasne, Histoire des Champignons 
hypogeés, 41-50. 
37. Theascophorous Fungi are represented 
in their simplest form by the Uredineae, a 
family which has been studied by numerous 
observers on account of the destructive pro¬ 
perties of the plants belonging to it. The 
mass which is formed by the growth of the 
reproductive organs of Uredo under the epi¬ 
dermis of the leaves of the plants upon which 
it grows parasitically, may be aptly compared 
to a pustule, a grumous-looking substance, 
occupying, as it were, the place of the pus. 
On more minute examination of the cavity, 
we find that it is bounded by a kind of irre¬ 
gular wall or lining of pyriform cells, the 
smaller ends of which rest upon a reticular 
cushion of mycelium. These are probably the 
enlarged extremities of the mycelium filaments, 
with which many of them can be distinctly 
traced to be connected. Towards the base of 
the cavity other cells are developed, resem¬ 
bling those first mentioned in their general 
form, as well as in their relation to the myce¬ 
lium. In these, however, the membrane is 
produced inferiorly, so as to form a tubular 
pedicle ; while in the club-shaped upper ex¬ 
tremity it is lined by a considerable deposit of 
granular protoplasma, so that here the central 
cavity is very much smaller than that of the 
external membrane. It is in this cavity that 
the spore is formed, at first not exceeding it 
in size, but afterwards increasing at the ex¬ 
pense of the protoplasma, so as almost to fill 
the theca. In other genera, as in Phragmidium, 
there are pedicled cells of a similar form, and 
originating in a similar manner, which, how¬ 
ever, instead of one spore, develop a number 
in their interior ; these spores are arranged in 
linear series, and are formed in the same 
manner. The protoplasma, however, never 
disappears completely, but remains as a more 
or less consistent membrane, glueing the ripe 
spore to the spore-case which encloses it. 
Some of the Uredineae possess a cyst which re¬ 
minds us of the perithecium of the Sphœriaceæ, 
to which they are evidently closely related. 
The cyst is formed (Œcidium) of a single 
layer of roundish cells.* 
38. From the Uredineae we pass by a natural 
transition to the Discomycetes and Pyreno- 
mycetes. These plants have been investi¬ 
gated with much success by MM. Tulasne, 
who have shown that they possess the 
closest relationship not only to the Lichens, 
but to the most simple thread Fungi. The 
very remarkable facts which these observers 
have discovered, render the study of these 
plants more satisfactory and instructive than 
that of any other family of the class. The 
Pyrenomycetes are represented by Sphoeria, 
the receptacle of which consists, as is well 
known, of a spherical cyst, which is open 
above. Its wall is frequently prolonged up¬ 
wards into a tubular beak, which projects 
beyond the surface of the bark or wood in 
which the whole plant is embedded. The 
membrane of the cyst (perithecium) is usually 
* L. R. Tulasne, Recherches sur les Uredinées 
&c. Ann. des Sc. Nat. 3me. S. t. vii. p. 12.
        

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