No. 463.] STUDIES ON PLANT CELL.— VI. 455 
in a number of structures with their contents somewhat massed 
at one side or in the center but such conditions must not be 
confused with the remarkable process of synapsis in the spore 
mother-cell. Among all the excellent studies of gametogenesis 
in the Peronosporales I cannot find any clear evidence of a re- 
duction of the chromosomes at gametogenesis. 
Quite different is the account that Trow (:04) brings forward 
to support his view of chromosome reduction during gametogen- 
esis in the Saprolegniales. Trow describes two mitoses in the 
oógonium of Achlya debaryana : in the first the number of chro- 
mosomes is eight which becomes reduced to four in the second. 
Trow's account of a second mitosis in Achlya is very different 
in a number of particulars from the results of all investigations 
on gametogenesis in the Peronosporales and Saprolegniales. 
Two centrosomes with radiations are said to appear at the poles 
of the spindle at anaphase, structures which were not present in 
the first mitosis. Some of these asters become the center of 
the egg origins and are later accompanied by deeply staining 
material constituting a body which Trow terms an ovocentrum 
and which perhaps corresponds to a coenocentrum. Relatively 
few of the nuclei in the oógonium are said to pass through this 
second mitosis and some of their products, with the accom- 
panying asters, break down. The remainder become the func- 
tional gamete nuclei of the eggs. There are many complex 
activities described by Trow in connection with the appearance 
of the asters during the second mitosis and also at the side of 
the sperm nuclei which are said to enter the oógonium, events 
that cannot be correlated with the processes of gametogenesis 
and fertilization as we understand them for the Peronosporales, 
They are treated briefly in a review | myself (Bor. Gas vol. 
39, p. 61, 1905), where, however, I misunderstood a distinction 
that Trow draws between the aster and the ovocentrum (see an 
answer by Trow, Bot. Gaz., vol. 39, p. 300, 1905). My impres- 
sion is that either Trow has been mistaken in his interpretations 
conception of gametogenesis is in the Saprolegniales and Perono- 
sporales, but which are not fully explained by Trow's paper. 
Let us now think of gametogenesis among the thallophytes 
