No. 460.] STUDIES ON PLANT CELL.— V. 237 
Spirogyra which should be thoroughly investigated. Chmielew- 
ski (90b) in a paper published in Russian and reviewed in the 
Bot. Centralb., vol. 50, p. 264, 1892, described a fusion of the 
gamete nuclei in the zygospore and an immediate mitosis, with- 
out a périod of rest, followed at once by a second division of the 
daughter nuclei. These mitoses give the zygospore four nuclei, 
two of which unite to form a final resting nucleus in the zygo- 
spore while the remaining two fragment and their products 
finally break down. This behavior offers an exception to all 
sexual processes so far known in the plant kingdom. There are 
some features which suggest a possible confusion with events as 
described in the zygospore of the desmid and the auxospores of 
certain diatoms. 
The fusion nucleus in the zygospore of Closterium and Cos- 
marium (Klebahn, '91) divides into four at the time of germina- 
tion and two of these break down while each of the others 
becomes the nucleus of the two new desmids that are formed. 
There is then in the desmids the division of the fusion nucleus 
into four but no secondary nuclear fusions as Chmielewski 
reports for Spirogyra. In certain diatoms, Rhopalodia (Kle- 
bahn, '96) and Cocconeis (Karsten, :00), there is a preliminary 
division of the nuclei in each of the two cells which form the 
auxospore. In Rhopalodia the mitoses are carried so far that 
four daughter nuclei are formed in each diatom and the pro- 
toplasm divides into two cells each of which fuses with a 
corresponding cell of the companion pair. In both types the 
superfluous nuclei break down so that the conjugating cells have 
each a single functional gamete nucleus. There are then com- 
plications in the Conjugales and the diatoms, which make nuclear 
studies of the sexual processes exceptionally difficult and we seem 
justified in reserving our judgment of the results of Chmielewski 
until confirmed. It seems possible that the mitoses following the 
germination of the zygospore in the Conjugales with the attend- 
ant nuclear degeneration are reducing divisions in a simple and 
primitive type of sporophyte generation but more detailed studies 
of nuclear behavior during the formation and germination of the 
zygospore will be necessary to settle the discussion. 
We have now finished our account of nuclear fusions in the 
