432 BOTANICAL GAZETTE [JUNE 
pletion. During the entire process of the tetraspore formation, the 
mother-cell is connected by a strand of protoplasm with the stalk- 
cell, and probably gets much nourishment through this strand, for the 
tetraspore mother-cell increases greatly in size. Finally, the cleavage 
furrows meet in the center between the four daughter nuclei, thus 
dividing the protoplasm into four tetraspores. 
ABNORMALITIES. 
Normally, the male and female organs and the tetraspore are never 
developed in the same plant, but it often happens that the male and 
female organs are produced on the same individual, and cccasionally 
antheridia are formed on the same branch with procarps and cysto- 
carps. The sexual cells in these cases are developed normally, the 
number of the chromosomes being always 20. Cystocarpic plants 
have also been found producing cells whose lineage is identical with 
that of the tetraspore mother-cell. However, I have never seen evi- 
dence of nuclear division in such a cell; cleavage furrows appear 
and cut deeply into the protoplasm, which nevertheless remains un- 
divided, so that tetraspores are not formed. Whether this cell may 
escape and germinate as a monospore has not yet been determined. 
CONCLUSION. 
The nuclear conditions in the life history of Polysiphonia may be 
summarised as follows: 
1. The germinating carpospore contains 40 chromosomes, and 
the tetrasporic plant the same number; so it may be inferred that the 
tetrasporic plants. come from carpospores. 
2. The germinating tetraspore contains 20 chromosomes, and the 
sexual plants (gametophytes) the same number; so it may be inferred 
that the sexual plants come from tetraspores. 
3- The nuclei of the gametes (sperm and carpogonium) contain 
each 20 chromosomes. The fusion nucleus (sporophytic) in the fer- 
tilized carpogonium presents 40 chromosomes, and gives rise to a series 
of nuclei. Some of these enter the carpcspores, which are conse- 
quently a part of the sporophytic phase to be continued in the tetras- 
poric plant. The gametophytic nuclei in the central cell of the 
cystocarp (with 20 chromosomes) either break down or form the 
paranematal filaments. 
