Generations , and General Cytology of the Uredineae. 345 
at the point of contact of the two nuclei disappears and the two nuclei fuse, 
the two nucleoli being distinguishable for some little time after fusion (Fig. 
91 a,b, and c). The fusion-nucleus then increases in size and goes through 
changes exactly similar to those of Phragmidium . A single large nucleolus 
appears, and the chromatin becomes resolved into a thick, continuous, 
spireme thread (Fig. 92). Here, also, this condition is merely temporary, 
for the thread after a time becomes replaced by a fine network, with usually 
only small inconspicuous nucleoli (Figs. 14 and 1 5), as described under the 
mature teleutospore. As in the case of Phrag. violaceum , these nuclear 
changes must be looked upon as a process of synapsis. 
METHOD OF ‘CONJUGATE 5 DIVISION. 
The method of division of the paired nuclei is of the same simple type as 
that described for the single nuclei of the spermatial hyphae, but the two 
nuclei are always to be found in the same stage of division and in very close 
association during the process. This division can best be observed in the 
development of the aecidiospores, uredospores, and teleutospores. 
The first step in the process is the disappearance of the nuclear membrane 
and the condensation of the chromatin of each nucleus into a homogeneous, 
irregular mass, with the natural result that the single nucleolus (which is 
always present at least in the nuclei of the cells connected with spore- 
formation) comes to lie free in the cytoplasm (Figs. 93 95 a). Sometimes 
the chromatin can be observed in a state where it is not yet completely 
homogeneous and still retains in part the form of the original nucleus (Fig. 
98 a). In the next stage the chromatin mass becomes more regular (Figs. 
93 95 &)t an d in favourable cases can be seen to be connected with 
a thread-like structure (Figs. 72, 93 b) } which has the staining reactions of 
kinoplasm, and is no doubt to be considered as of the nature of a simple 
spindle. The chromatin mass then becomes elongated to form a thick 
rod which is apparently stretched out on the spindle, for the latter is 
completely obscured (Figs. 93 c, 95 c). Each chromatin rod then becomes 
drawn out into two more or less pear-shaped masses (Figs. 93 d , 95 d), 
which at first remain connected by a fine thread which has the staining 
reactions of kinoplasm (it takes the gentian in the triple stain), and is no 
doubt the drawn-out spindle (cf. divisions in promycelium). As the two 
masses move still further apart the connecting thread becomes very faint 
and ceases to be continuous (Fig. 93 d). At this stage, or somewhat earlier, 
the rejected nucleoli, which have hitherto lain almost unaltered in the 
cytoplasm, begin to decrease in size and finally disappear, though they may 
remain visible up to the stage in which the new nucleoli have begun to 
appear in the daughter-nuclei (Fig. 93 e\ 
