4l> PUCCINI A POARUM 



life-history is in all essentials identical with that of P. Garicis, 

 but it differs in one striking particular — there are two genera- 

 tions of each stage during the year. 



The spermogones and secidia 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 secidia, also accompanied by spermogones, appears 

 from end of July to September, followed again by uredo- and 

 teleutospores in September to November. The latter rest 

 • lining 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 Mc Alpine, where the Coltsfoot does not exist, and the uredo- 

 stage is most common in the winter months, i.e. 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 secidium, especially in July and 

 August. 



The aecidium 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. Garicis in their shape, 



