Generations , and General Cytology of the Uredineae. 333 
the first and second division, probably represent the chromatin derived 
respectively from the two nuclei which fused in the teleutospore. It 
was these two masses which Sapin-Trouffy mistook for two chromo- 
somes, as a comparison of his figures with Figs. 30, 32, and 41 a clearly 
show. 
The method of spindle-formation, in which the spindle is formed free 
in the cytoplasm between two centrosomes and later comes into relation 
with the dividing nucleus, is of great interest. It is clearly of the type 
described, in animals, by Hermann and others for the Centralspindel. 
The only case in plants with which it is at all comparable is the 
peculiar method of spindle-development described by Lauterborn (28) 
for Diatoms 1 . 
Since the work of Sapin-Trouffy, who failed to discover either a spindle 
or chromosomes in the divisions in the promycelium, it has been shown by 
Juel (25), in Coleosporium Euphrasiae y that a spindle and polar radiations 
were present, and that the division was of a much more typical nature 
than Sapin-Trouffy had described. He was not, however, able to determine 
the behaviour of the chromatin part of the nucleus. When this work was 
complete a paper appeared by Holden and Harper (22), in which it was 
shown that in the divisions of the developing teleutospore of a form of 
Coleosporium on Callistephus, &c., to which they give the name C. Sonchi - 
arvensis , a spindle with centrosomes, polar radiations, and showing numerous 
chromosomes was to be observed, as in Gymnosporangium. They did not, 
however, trace the origin of the spindle, and they give but a few figures 
of the behaviour of the chromatin, for Coleosporium does not seem to be 
nearly so favourable an object of study as the form here investigated. They 
are of the opinion that both divisions are typical in nature. 
Sporidia formation. There is nothing worthy of special comment in 
the normal formation of sporidia. A primary sporidium is shown, in section, 
at Fig. 25. 
In some cases the original four cells of the promycelium may round 
themselves off, separate, and put out germ-tubes, thus behaving like 
sporidia. Long germ-tubes may also be put out by the four cells while 
they are still attached, as shown in Fig. 44. Although the exact conditions 
were not investigated, this method of shortened development seems to be 
dependent on conditions of moisture, and is probably a response to growth 
under water or at least in a very moist atmosphere. It has been shown in 
an earlier paper (7) that promycelia actually growing under water develop 
to a great length, but rarely divide, and never form sporidia. A single case 
was there figured for Phragmidium, where the promycelium had divided 
1 P. Denke (Beihefte z. Bot. Centralbl., xiii, 1902, p. 182) has described the development of an 
extra-nuclear spindle, though, of course, without centrosomes, in the division of the microspore and 
megaspore mother-cell of Selaginella. 
