340 Olive— Sexual Cell Fusions and Vegetative 
a Blackman ‘ nuclear migration ’ occurs adjacent to a case of ‘ cell fusion ’ 
similar to that described by Christman. 
Figs. 35 and 36, as indicated above, are quite similar to each other as 
to their method of fusion. In Fig. 35, however, the walls below, between 
the two gametes, are shown as one ; while in the other figure the walls are 
quite distinct from each other. In both cases, further, a concentration of 
finely granular protoplasm is evident in the upper part of the fused cells, 
where the protoplasts have mixed in, and on either side of, the conjugation 
pore. In Fig. 35, finally, each nucleus shows a small, deeply stained, 
dumbbell-shaped body — the dividing centrosome — whose significance will 
be discussed in some detail later. 
Fig. 37, from a preparation of Phragmidium potentillae-canadcnsis , 
although poorly stained as to the nuclei, shows very clearly the beginning 
of the formation of the conjugation pore. Here again the relation of the 
two cells to each other is in doubt. Although they appear to be in the same 
cell row, the lower cell may just as well be from one of the obliquely lying 
hyphae which come up from below at varying angles. In this figure, 
a granular body, resembling a nucleole, lies in the pore connecting the two 
cells. In other cases I have found unmistakable cases of nucleoles thus 
thrown out at the beginning of the nuclear division, which starts with the 
earliest indication of cell fusion. But in this instance vacuolated nucleoles 
are apparently still present in both poorly-defined nuclei, so that it seems 
likely that the granular body is merely a cytoplasmic inclusion. 
. Fig. 38 is from the same preparation of Phragmidium potentiliae- 
canadensis as is Fig. 3 7. Such poorly fixed and stained preparations were 
thus selected because the remnant of the partition wall between the two 
fused cells stands out in each case with great distinctness. The leaf in this 
instance was fixed with Juel’s fixative and stained with Flemming’s triple 
stain, as was also the material from which Figs. 28-32 were drawn. 
Figs. 39 and 40 represent fusing cells of the micro- form, Puccinia 
transformans. In the first-named figure, the nuclei, except for their bright 
red nucleoles, are not well defined. Fusion has apparently taken place in 
this instance between the tips of two parallel hyphae. In Fig. 40, on the 
other hand, an end cell of one hypha (which apparently comes in obliquely 
from below) has fused with the penultimate cell of another. The uninu- 
cleated character of the gametophytic cells is also well shown in the latter 
figure. While it is not my present purpose to discuss this micro- form in 
detail, I may say in passing that the fusion is followed at once by a growth 
resulting in teleutospores, each borne on a stalk consisting, at least in some 
instances, of about three binucleated cells. The sporophytic development 
consists, therefore, of a few binucleated cells only. This case is possibly 
similar to that of Puccinia malvacearum , in which Blackman finds that the 
change from a uninucleated to a binucleated condition occurs at the base of 
