1906] YAMANOUCHI—POLYSIPHONIA VIOLACEA 429 
between dissolve, the contents of the sperm cell enter the cytoplasm 
of the trichogyne, and the sperm nucleus passes down into the car- 
pogonium where the fusion of the male and female nuclei takes place. 
The trichogyne nucleus may be found even after the sperm nucleus 
has passed into the carpogonium. But later, when the trichogyne 
becomes separated from the carpogonium, its nucleus can scarcely 
be distinguished. The trichogyne then shrivels and dies. 
The carpogonium after fertilization unites with one of the auxiliary 
branch cells which lies beneath, and the latter also fuses with the peri- 
central cell, thus providing a passage into the pericentral cell for the 
fusion nucleus of the fertilized carpogonium. Then the remain- 
der of the auxiliary branch cells fuse with one another and with 
the pericentral cell, which results in a large fusion cell, the central 
cell, that naturally contains a number of nuclei. 
The nuclei in the central cell are of two sorts with respect to origin: 
first, there is the fusion nucleus from the carpogonium (sporophytic) ; 
and second, there are a number of nuclei derived from the auxiliary 
cells, which are of course gametophytic. The fusion nucleus gives 
rise to a series of nuclei by typical mitoses which present 40 chromo- 
somes as a sporophyte number. The central cell now develops 
several lobes into which these sporophytic nuclei pass. Further 
mitoses increase this number, and each lobe then cuts off a carpospore 
terminally, which is attached to the central cell by a short stalk. 
After the carpospores are formed, the central cell increases in size 
greatly, absorbing the stalk cells, and even the central axial cell also 
becomes involved -in_ this general cell fusion. These very exten- 
sive cell unions are probably concerned with the nourishment of 
the carpospores. 
Some of the gametophytic nuclei derived from the auxiliary cells 
remain in the central cell, increasing in size and finally breaking down 
after a number of peculiar changes. Others of the gametophytic 
nuclei divide amitotically to form the paranematal filaments which 
lie under the wall of the cystocarp. 
TETRASPORE FORMATION. 
The tetrasporic plant normally never produces antheridia or pro- 
carps, and the cytological studies on the vegetative cells give proof 
that it differs in an important respect from the sexual plants. The 
