ALGA3 : THEIR STRUCTURE AND MODE OF REPRODUCTION. 35 
immotile. They consist of an oblong or globular external cell 
or sac, at first filled with granular contents, which subse- 
quently separate into four portions, often arranged as the 
comers of a tetrahedron, but also frequently in a row, or like 
the quadrants of a sphere. Very rarely the number is greater 
or smaller than four. They are not placed in special recep- 
tacles, sometimes exposed on the surface of the frond, more 
often imbedded in its tissue, often in branches of peculiar 
shape, often congregated in great numbers. In the Corallines 
they are enclosed in elliptical conceptacles. 
The sexual reproduction of the Floridese presents some 
remarkable features. The male and female organs, called 
Antheridia and Trichogynes, are produced on different indi- 
viduals to the tetraspores. The antheridia are either single 
cells at the ends of the branches, each producing only one 
antherozoid, or these parent cells of the antherozoids are con- 
gregated together in large numbers on a common axis as the 
terminal member of a very short branching system. 
The antherozoids are minute roundish bodies without cilia and, 
like the tetraspores, without any power of independent motion, but 
are moved along passively by the water. In fig. 13 a represents 
the antheridium with a number of antherozoids escaping from 
it. The female organ, or trichogyne, is placed at the summit 
of a special organ, the Cystocarp, which, after fertilisation, pro- 
duces the spores ; in these organs it may be said that we have 
the first rudimentary indication of organs corresponding to the 
stigma and ovary of flowering plants, the antheridium and 
antherozoids corresponding to the anther and pollen-grains. 
The cystocarp consists, in its rudimentary condition, of branches 
formed of only one or two cells, which subsequently divide into 
a larger number. One of these cells at the side of the cysto- 
carp subsequently elongates greatly into three, the two lower- 
most of which form the Trichophore, while the uppermost 
elongates still further into a hair-like prolongation, the Tri- 
chogyne (fig. 1 3 c), which therefore grows up by the side and 
not at the summit of the cystocarp. The spores are produced 
in the central cell of the cystocarp, and therefore not in imme- 
diate connection with the trichogyne or trichophore. The 
antherozoids collect round the top of the trichogyne, as repre- 
sented in the figure ; and their fertilising power is transmitted 
through the tube to the spores, in some unknown way, possibly 
analogous to the part performed by the pollen-tube of flowering 
plants. In Dudresnciya the process is, according to Thuret and 
Bornet, still more complicated. In this genus the cystocarps 
are produced on altogether different branches from the tricho- 
phore. After the long spiral trichogyne has been fertilised, 
branches spring out from it, and from these are produced tubes 
D2 
