STRUCTURE. 



39 



Fia. 



). — XenodocJtua car 

 bonarius. 



yellow Uredine, of which it is a condition. Probably, in every 

 species of the Puccinicei, it may hereafter be proved, as it is 

 now suspected, that an unicellular Uredine 

 precedes or is associated with it, forming 

 a condition, or secondary form of fruit 

 of that species. Many instances of that 

 kind have already been traced by De Bary,* 

 Tulasne, and others, and some have been a 

 little too rashly surmised by their followers. 

 In Phragmidium, the pedicel is much more 

 elongated than in Xenodochus, and the spore 

 is shorter, with fewer and a more definite 

 number of cells for each species ; Mr. Currey 

 is of opinion that each cell of the spore in 

 Phragmidium has an inner globose cell, 

 which he caused to escape by rupture of the 

 outer cell wall as a sphaeroid nucleus,f leading to the inference 

 that each cell has its own individual power of germination and 

 reproduction. In Trvphragmium, there are 

 three cells for each spore, two being placed 

 side by side, and one superimposed. In one 

 species, however, Triphragmium degluhens 

 (North American), the cells are arranged as 

 in Phragmidium, so that this represents really 

 a tricellular Phragmidium, linking the pre- 

 sent with the latter genus. In Puccinia 

 the number of species is by far the most 

 numerous ; in this genus the spores are uni- 

 septate, and, as in all the Puccinicei, the 

 peduncles are permanent. There is great 

 variability in the compactness of the spores 

 in the sori, or pulvinules. In some species, 

 the sori are so pulverulent that the spores 

 are as readily dispersed as in the Uredines, 

 in others they are so compact as to be separated from each 



* De Bary, " Ueber die Brandpilze," Berlin, 1853. 



+ Cnrrey, ia " Quart. Journ. Mior. Sci." (1857), vol. v. p. 119, pi. 8, fig 13. 



Fio. 



21. — Phragmidium 

 bulbosum. 



