THALLOPHYTES 
59 
Female plant. In Polysiphonia the procarp includes several cells 
in addition to the carpogonium and trichogyne. The carpogonium 
arises from a large cell of the axis, called the pericentral cell, and around 
150 
151 
FIGS. 149-151. Polysiphonia: 149, showing the polysiphonous bodies bearing two 
clusters of antheridia; 150, cystocarp, showing the sterile jacket investing the group of 
carpospores, and also an isolated carpospore; 151, two mother cells forming tetraspores. 
this cell a group of auxiliary cells is formed, one of which crowds between 
the pericentral cell and the carpogonium. This whole complex struc- 
ture trichogyne, carpogonium, pericentral cell, and auxiliary cells 
is the procarp (fig. 153). 
Fertilization occurs as in Nemalion, the floating sperm (antheridium) 
coming in contact with the trichogyne and discharging into it its contents. 
The male nucleus passes to the carpogonium and there fuses with the 
female nucleus. The fusion nucleus divides within the carpogonium, 
and then what are called cell fusions begin. A passageway is opened 
from the carpogonium, through the intervening auxiliary cell, and into 
the pericentral cell, and by this means the two daughter nuclei of the 
fusion nucleus are free to migrate into the pericentral cell. At the same 
time, the auxiliary cells begin to fuse with one another and with the 
pericentral cell, until a large, irregular, multinucleate cell or chamber is 
formed. In this irregular chamber the two nuclei from the carpogonium 
begin a series of successive divisions, which result in a large number of 
