348 Olive . — Sexual Cell Fusions and Vegetative 
stage, on the other hand, from the sporidia, or basidiospores, up to the 
base of the aecidium constitutes the gametophyte generation. Besides 
the basidiospores, this stage bears only one kind of uninucleated spore-like 
bodies — the so-called spermatia — which Christman regards as the now 
functionless gametophytic pycnidia ; whereas the sporophyte stage may 
bear from one to several kinds of binucleated spores. The process of 
sexual cell fusion which initiates the binucleated condition gives the 
stimulus of ‘ fertilization ’, or the first essential step of the sexual cycle. 
This is followed, either shortly (in the lepto- and micro- forms) or after 
a more or less prolonged period of development (in the eu- t brachy -, and 
hemi-i orms), by the other steps of the sexual process, i. e. nuclear fusion, 
and, according to Blackman, chromatin fusion. 
The main question here confronting us involves, therefore, the method 
of fertilization — as to whether ‘ a female cell is fertilized by the nucleus of 
an ordinary vegetative cell ’, as Blackman maintains ; or whether the two 
fusing cells are equal gametes, as Christman holds. The one evidently 
interprets the process as tending to the oosporic type and toward the Red 
Algae ; the other holds that two equal gametes fuse to form a non-resting 
zygospore. 
Although in Figs. 28, 31, and 32 the lower cell appears to be some- 
what smaller than the upper gamete, it is sufficiently obvious that such 
sections as are here represented will not enable one to judge certainly 
as to the shape and comparative size of the two fusing cells. In his first 
paper (’ 04 ), Blackman makes a strong point of his observation that the 
lower cell is smaller than the upper cell ; and, further, that even the two 
nuclei in the young fusion cell are unequal in size, remarking that the 
smaller nucleus is denser and that it shows no nucleole or only a small one. 
In each of the Figs. 31-33, 36, and 40, one of the two nuclei likewise 
appears to be smaller than the other ; although the nucleoles are not 
lacking in these cases, nor are the smaller nuclei conspicuously denser than 
the others. Some instances of fusing cells which I have observed, in which 
one of the nuclei appears to be smaller than the other, are undoubtedly 
to be explained as due simply to the unequal cutting in two of the smaller 
nucleus ; or it may be that an end view of an elongated nucleus is presented. 
One nucleus, it is true, may, during the passage from one cell to another, 
be somewhat denser than the other (Figs. 33 and 34) ; but, in my opinion, 
there are no differences in shape or size, either between the two fusing cells 
or between their nuclei, which cannot reasonably be explained as due 
to sectioning or to greater or less rotundity of the nuclei. 
It is clear, therefore, to my mind, that Christman’s contention as to the 
equality of the two fusing protoplasts will hold, at least for the four species 
herein considered. Hence Blackman’s interpretation of one of the cells 
as a differentiated ‘ fertile, or female ’ will not apply in these cases. But 
