830 REPRODUCTION OF ALG. 
tions, and it is most probable that the reproduction of Agaricus 
is asexual. The process of reproduction in the Fungi and 
Lichens has already been sufliciently noticed (see pages 378- 
390) ; but the Algee and Characez require further explanation. 
(1) Reproduction of Alge.—The reproduction of Algze takes 
place in the following ways: namely, by division (page 765 and 
fig. 1125), free cell-formation (page 773), conjugation, and by the 
direct impregnation of naked spores or germ corpuscles by ciliated 
antherozoids. Each process is also liable to modifications, 
a. Conjugation.—This process occurs in the Algze, as Diatoms, 
Desmids, Spirogyra, &e. (See pages 394 and 765, figs. 862, 863, 
and 1126.) It consists in the union of the contents of two in- 
dependent unicellular organisms ( fig. 1126), or of the cells of two 
filaments (fig. 863), and the formation of a germinating spore 
by their mutual action. No difference can be detected in the 
structure of the conjugating cells, although in many, if not all 
cases, it is believed that there is some unobserved difference con- 
stituting the one as the male, the other as the female element. 
Two methods of conjugation may be noticed among the 
Alge. In the first mode, as seen in Desmidiez, &e. (fig. 1126), 
two individuals, each of which is composed of a single cell, ap- 
proach each other, the external cellulose membranes bounding 
their respective cells then burst at their point of contact, and 
the contents of the two issue from the orifices thus produced, 
intermingle in the intervening space, and form ultimately, by 
their mutual action, a rounded body, called a zygospore, resting, 
or inactive spore, which ultimately germinates. The contents of 
the spore are green and granular at first, but ultimately become 
brown, yellow or reddish. These resting spores are furnished 
with a coat of cellulose which in some cases divides into two 
layers, the exospore and endospore; they are sometimes called 
sporangia, because they ultimately produce two or more germs 
in their interior, and are not therefore simple spores. 
In the other mode of conjugation, which occurs in Zygnema 
and Spirogyra (figs. 862 and 863), the cells of two filaments 
develop on their adjoining sides a small tubular process; these 
ultimately meet and adhere, and the intervening septum existing 
at the point of contact becoming absorbed, the two cells freely 
communicate. The contents of the cells then contract into a 
mass, and ultimately combine together, either by the passage of 
the contents of one cell into the other, or by the mixture of the 
contents of the two cells in the tubular process between them. 
Under either circumstance, the mixture of the contents of the 
two cells results in the formation of a zygospore or resting spore, 
which ultimately germinates and becomes an individual resem- 
bling its parents. 
b. Impregnation of naked spores or germ-corpuscles by ciliated 
antherozoids.—There appear to be two forms of this fecunda- 
tion : thus, in certain Algz, as Vaucheria, the fecundation takes 
