Nemalion multi fidum, Ag. 347 
5. The fusion of gamete nuclei involves a fusion of the chromatic 
nucleoles. 
6 . Chromosome reduction occurs with the first division of the zygote 
nucleus. The threads of the delicate reticulum thicken and shorten and 
finally take on a parallel arrangement. A fusion of threads then apparently 
takes place, followed by condensation of material to form eight bivalent 
chromosomes. These then become differentiated as eight pairs of chromo- 
somes distributed about the nuclear cavity in a clear stage of diakinesis. 
The sixteen chromosomes of these eight pairs are segregated by the first 
mitosis, which is therefore a reduction division. 
7. The chromosome number is eight throughout all nuclear divisions 
in the history of the plant, except the first mitosis of the zygote nucleus. 
8. Vegetative mitoses are best studied in the cells of the developing 
cystocarp. The resting nucleus contains a large nucleole and a reticulum 
of delicate threads. Approaching mitosis is indicated by the appearance 
where the threads cross of numerous granules which, increasing in size, are 
brought together by the contraction of the threads, fusing successively until 
the eight chromosomes are differentiated. The spindle is intranuclear, and 
conspicuous polar structures are present. The nucleolus, presenting an 
empty appearance, takes a position during metaphase on the edge of the 
equatorial plate, outside of the spindle, and apparently disappears with the 
breaking down of the nuclear membrane. The two sets of daughter 
chromosomes during telophase severally organize a chromatin nucleole from 
which material is later distributed as a network throughout the resting 
nucleus. 
9. The nucleus left in the carpospore cyst after the first division of the 
carpospore nucleus may again divide, but the resulting nuclei do not become 
completely organized and soon break down. 
10. Since reduction, as in Scinaia and Coleochaete , takes place with the 
first mitosis of the zygote nucleus, the cystocarp of Nemalion is not sporo- 
phytic in character, and there is no cytological alternation of generations 
in this plant. 
University of Pennsylvania, 
July , 1918. 
Literature cited. 
Allen, C. E. (1905) : Die Keimung der Zygoten bei Coleochaete. Ber. deut. bot. Gesell., xxiii. 286. 
Boubier, A. M. (1899): Contributions a 1’ etude du pyrenoide. I. La membrane pyrenoidienne. 
Bull. Herb. Boiss., vii. 451-8. 
Bourquin, Helen (1917) i Starch Formation in Zygnema . Bot. Gaz., lxiv. 426-34. 
Bruns, E. (1894) : Ueber die Inhaltskorper der Meeresalgen. Flora, lxxix, Erg.-bd., pp. 159-78, 
