39 
Sexuality of the Uredineae. 
As development of the aecidium proceeds the fertile cells, aecidiospore- 
mother-cells, and spores become arranged in perfectly regular rows, and the 
hyphae below the aecidium become gradually emptied of their contents, 
which pass up into the fertile cells (Fig. 7 ). The intercalary cells are small 
and disappear early ; the division which separates them from the aecidio- 
spores being usually found in the second or third row of cells above the 
layer of fertile cells. 
The development of the pseudoperidium from the outermost layer of 
* fertile cells ’ is well shown in Fig. 7 . These pseudoperidial cells exhibit 
very thick, finely striated walls, and their contents, with the two nuclei, 
soon become disorganized. In the young state, before it is ruptured, the 
pseudoperidium stretches like a protecting dome over the more or less 
hemispherical mass of developing fertile cells and aecidiospores (Fig. 7 ). 
The cells of the pseudoperidium appear to represent in this form aborted 
aecidiospore-mother-cells rather than aecidiospores, for no clear cases of 
the formation of intercalary cells were observed in them. 
Some evidence was obtained in support of Richards’ (7) observa- 
tion that the terminal spores cut off from the central fertile cells (basidia of 
older authors) form the central part of the pseudoperidium, the peripheral 
part only being formed by the outermost layer of fertile cells ; this point, 
however, was not investigated in detail. 
Various stages of conjugate division (Figs. 9 a-d) were observed in the 
divisions which cut off the intercalary cells. The small simple spindles 
and the chromatin masses, without, apparently, any differentiation into 
chromosomes, were to be seen as described in the earlier paper ( 1 ) ; but 
in this case the minute size of the chromatin mass as compared with the 
large nucleolus is very striking. 
As in the case of Phragmidium violacemn, fertile cells, and the spores 
derived from them, were sometimes observed which contained three nuclei, 
and in very rare cases four nuclei were to be seen. The trinucleate cells 
were not uncommon, and it was not unusual to observe three or four rows 
of such cells in one aecidium. Whether these abnormal numbers are due 
to the division of one or both of the conjugate nuclei, or to a process of 
multiple fertilization, it is at present impossible to say. It is to be noted 
that cells with more than two nuclei were observed by Richards (7) in 
some of the aecidia which he investigated, but Sapin-Trouffy makes no 
mention of them. The fate of the aecidiospores with more than two 
conjugate nuclei is also unknown ; they might conceivably give rise to 
a mycelium with, for example, trinucleate cells and bearing trinucleate 
uredospores and teleutospores, but such has not been met with. It is 
possible, on the other hand, that they are incapable of germination. 
