POLYSIPHONIA 327 
on the end of a branch and at first apparently consists of two 
cells, a basal one called carpogonium and a much elongated 
terminal one called trichogyne. The two cells are not separated 
by a wall and the nucleus soon disappears from the trichogyne 
and the two cells then appear as a single one with a bulbous base 
and a hair-like extension. The carpogonium corresponds to the 
odgonium in other Algae, for it contains a protoplast which func- 
tions as an egg. 
The antheria, which are borne in clusters at the ends of short 
branches, are single cells, and the protoplast of each antheridium. 
becomes binucleate and functions as a sperm. After these 
binucleate protoplasts are discharged from the antheridia, they 
depend upon water currents to carry them to the female sex 
organs as they have no cilia. When they come in contact with 
the trichogyne, the two walls in contact are resorbed, and the two 
male nuclei of the sperm pass into the trichogyne through the 
perforation. A number of sperms may discharge their nuclei 
into the same trichogyne, but only one male nucleus passes on 
into the carpogonium and fuses with the female nucleus. After 
fertilization, the carpogonium develops numerous short filaments, 
each of which bears a spore, called a carpospore, at its tip. The 
carpospores, short filaments, and the carpogonium together con- 
stitute the structure known as a cystocarp. The carpospores 
upon germination develop sexual plants, thus completing the life 
history. 
Polysiphonia. — This plant (Fig. 283) is a representative of 
the complex forms of Red Algae. Itisa much-branched complex 
filament and is so named because it has a central row of elongated 
cells (axial siphon), enclosed by peripheral cells. This plant 
presents much differentiation and ordinarily a life history in- 
volves three types of individuals — male, female, and sexless 
plants. 
The male plants bear their antheridia on very short lateral 
branches which arise from the axial siphon and bear the an- 
theridia somewhat laterally on their tips. The protoplast of an 
antheridium contains only one nucleus and is not discharged as 
in Nemalion, but the antheridium breaks off bodily and is floated 
to the trichogyne. 
The female plant produces a procarp more complex than that 
of Nemalion. The procarp consists of other cells in addition to 
