46 PUCCINIA POARUM 
life-history is in all essentials identical with that of P. Caricis, 
but it differs in one striking particular—there are two genera- 
tions of each stage during the year. 
The spermogones and ecidia first appear on the leaves of 
Coltsfoot in May and June, and are followed by the Puccinia 
on neighbouring leaves of Poa in July and August. Then a 
second crop of ecidia, also accompanied by spermogones, appears 
from end of July to September, followed again by uredo- and 
teleutospores in September to November. The latter rest 
during the winter and infect the young Coltsfoot leaves again 
in the following spring. In countries that have a climate 
favourable for the growth of Poa, the uredospores may be found 
the whole year round, and the fungus can maintain itself by 
them alone. This is certainly the case in Australia, according 
to McAlpine, where the Coltsfoot does not exist, and the uredo- 
stage is most common in the winter months, 1e. June to 
September. In this country, the teleuto-sori are rather incon- 
spicuous, but can be found by searching carefully on the lower 
leaves of species of Poa round the spot where the Coltsfoot has 
been found affected by the ecidium, especially in July and 
August. 
The zcidium of this species has been examined cytologically 
by Blackman and Fraser, and according to them the binucleate 
condition of the fertile cells is produced by the migration of the 
nucleus from one fertile cell to an adjoining one in the hymenial 
layer, and also occasionally by a migration from one vegetative 
cell to another at a point where the conjugating cells were 
below the level of the hymenium, although only a little lower. 
Cells with three or four nuclei were met with by them, and true 
conjugate division was observed in such cases. 
In sections which I have examined of this species, I have 
seen evidence which seemed to indicate (although not with 
perfect, certainty) that conjugation also took place by the 
removal of a large part of the intervening cell-wall, and a con- 
sequent fusion of the cells as described by Christman and 
Dittschlag (Fig. 26). 
As will be seen from the figure, the cells of the peridium of 
this species differ slightly from those of P. Caricis in their shape, 
