436 BOTANICAL GAZETTE [DECEMBER 
SUMMARY. 
The nuclear conditions in the life history of Polysiphonia violacea 
may be summarized as follows: 
1. The carpospore on germination shows 40 chromosomes, and 
40 chromosomes appear in the vegetative mitoses of the tetrasporic 
plant; so it may be inferred that the tetrasporic plants come from 
carpospores. 
2. The tetraspore on germination shows 20 chromosomes, and 
20 chromosomes appear in the vegetative mitoses of the sexual plant; 
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 
fertilized carpogonium as a result has 40 chromosomes and gives 
rise to a series of nuclei in the central cell. Some of these enter the 
carpospores, which are consequently a part of the sporophytic phase 
to be continued in the tetrasporic plant. The gametophyte nuclei 
in the central cell of the cystocarp with 20 chromosomes break down. 
4. Tetraspore formation terminates the sporophytic phase with 
typical reduction phenomena, so that the tetraspores are prepared 
to develop the gametophyte generation. 
5. There is thus an alternation of a sexual plant (gametophyte) 
with a tetrasporic plant (sporophyte) in the life history of Polysiphonia, 
the'cystocarp being included as an early part of the sporophytic phase. 
THE UNIVERSITY OF CHICAGO. 
LITERATURE CITED. 
t. ALLEN, CHARLES E., Chromosome reduction in Lilium canadense. BOT. 
GAZETTE 37:464. 1904. 
, Nuclear division in ae ie mother cell of Lilium canadense. 
Annals of Botany 19:189. 1 
3. , Das Verhalten der i etsehésiiies wihrend der Synapsis in den 
Pollenmutterzellen von Lilium canadense. Jahrb. Wiss. Bot. 42:71. 1995- 
2. 
4. , Die Keimung der Zygote bei Coleochaete. Ber. Deutsch. Bot. Gesells. 
33:2 286. 1905. 
5. ANDREWS, FRANK M., Karyokinesis in Magnolia and Liriodendron, with 
special reference to the behavior of the chromosomes. Beih. Bot. Cen- 
tralb. I1:134. 1907. 
6. Bauer, E., Zur Frage nach der Sexualitat der Collemaceen. Ber. Deutsch. 
Bot. Gesells. 16: 363. 1898. 
