UKEDINE& 



385 



those already described in Collema. They are orange-coloured like the 

 sporocarps, and the pollinoids have never been known to germinate. 

 No corresponding female sexual organ occurs in any Uredine, though 

 the early stages of the development of the sporocarp are not sufficiently 

 known. No such body as Woronin's hypha in Xylaria, for example, has 

 ever been observed in the Uredineae, and the only suggestion of a female 

 sexual organ is to be found in the occasional occurrence in some 

 Uredines of short obtuse hyphae, projecting through the stomates of the 

 host like the trichogynes of Polystigma. These may be traced, it is true, 

 to young aecidia, but there may well be nothing more in the suggestion 

 than the mere protrusion of mycelial hyphae, since observations connecting 

 such filaments with an act of fertilisation are 

 wholly wanting. Massee ('Annals of Botany,' 

 1888, p. 47) has recently published an ac- 

 count of observations of a supposed sexual 

 process in Uredineae, involving the fertilisa- 

 tion of a carpogone by an antheridial branch ; 

 but the subject stands in great need of farther 

 investigation. 



The spores from the ripe sporocarp (aci- 

 diospores) germinate only on the leaves 

 or stems of grasses, and the germ-tubes 

 entering by way of the stomates give rise to 

 myceles, which attack the tissues of the host. 

 In the course of a week or more, cushion- 

 like masses of mycelial hyphae situated be- 

 neath the epiderm give rise to erect basids, 

 each of which bears a red uredospore (Uredo) 

 at the apex. On the rupture of the epiderm 

 the uredospores escape, and these alighting on 

 grass plants germinate, again enter by way of the stomates, and renew the 

 same generation. This process may and does go on indefinitely, and 

 thus much damage is annually caused by the attack of this fungus on 

 the corn crop. 



Later on there are developed' on the same mycele, first side by side 

 with the uredospores, then gradually replacing them altogether, two-celled 

 spores called teleutospores, and with their production the development of 

 the fungus ceases for a period. In this condition the winter is passed. 

 With spring they germinate, each of the two cells of the teleutospore 

 (Puccinia) giving rise to a short promycele, the terminal cells of which 

 bear on slender stalks a single sporid apiece. These sporids germinate 

 in turn on the leaves of the barberry, the germ-tubes piercing the epi- 



c c 



FIG. 315. Puccinia graininrs 

 Pers. t teleutospore ; it, uredo- 

 spores ( x 390). (After Sachs.) 



