Christman—Development of the Primary Uredospore. 519 
The fusion cell is a zygospore functionally, however we may 
interpret its phytogeny, and becomes in its germination, as we 
shall see, a basal cell for a series of uredospores. 
The upper region of this cell now enlarges, and the nuclei 
come to lie high up in the protoplast rather than to occupy the 
bases of the original gamete cells. This condition, as I have 
previously described (3), is also found in Uromyces caladii 
Earl. A prominence is now formed at the apex of the basal 
cell, which, in general appearance, is not unlike a bud. I have 
hot been able to observe the nuclear divisions which supply this 
bud with nuclei, but they are probably similar to those occur¬ 
ring later. At any rate, two nuclei come to lie in the bud, and 
two are left in the basal cell. The bud is now separated from 
the basal cell by a wall, and thus forms the first uredospore- 
mother-cell (fig. 3). A nuclear division (fig. 4), which seems 
in every respect to be a true conjugate division, now follows 
within the uredospore-mother-cell, and a daughter nucleus from 
each spindle comes to lie in the upper region, which is destined 
to become a spore. The other two nuclei are cut off by a cell 
wall in the lower elongated region of the uredospore-mother-cell 
(fig. 5). We see thus very clearly that the stalk cell so formed 
is directly comparable to the intercalary cell of the aecidium. 
In this case, it merely elongates to form a stalk upon which the 
uredospore is borne. 
About the time that the processes of nuclear and cell division 
are complete in the first mother-cell, the basal cell is pushing 
out a second bud beside the base of the first stalk cell (fig. 6). 
Early in the process of budding, the two nuclei of the basal cell 
are seen to lie near the base of the protuberance. When the sec¬ 
ond spore-mother-cell is about half grown, the division of the 
nuclei occurs. This division does not occur in the central re¬ 
gion of the fusion cell, but rather in the basal region of the bud 
(fig. 7). While the two nuclei divide simultaneously, it is not 
a conjugate division in the sense that the spindles are closely 
parallel during the division. The position of the spindles 
would indicate that in this case the division occurs while the 
nuclei are being carried into the base of the mother-cell by a 
