392 



UKEDINEAE. 



than those of G. tremelloidcs. Tlie aecidiospores — Roestclia 

 cormda — occur on species of Pyrns {Sorhus)] they are much 

 smaller than those of Rorstclia pcnicillata. The Roestclia 

 themselves are long, curved, and horn-like, while the walls of 

 the peridial cells are beset with short processes (Fig. 224). 

 Where Pijrus Aucuparia occurs mixed with Pyrus Malus, 

 it has been observed that Roestclia cornuta is confined . to the 

 former species exclusivi^ly. The Roestclia is the cause of a 



CP> jv^. 



l''io. 225. — Gyiiinoaporangmm juniperinum and 6. ti-cmcUoides. 1, Young spore- 

 cushions breaking through the bark ; 2, the same in swollen condition ; 3, gela- 

 tinous cushion arranged to show its lower surface ; 4, Juniper-needle with three 

 spore-cushions ; fi, young Juniper plant bearing cushions on its needles ; 6 to 10, 

 spores of various kinds, to show the variation in size, shape, and thickness of 

 wall ; 11, cell of a promycelium with a sporidium attached ; 1.', germinating 

 sporidium. (After Tubeuf.) 



marked deformation of leaves, petioles, and even (though rarer) 

 fruits of Pyrus Aucuparia and Aronia rotundifolia, both in 

 the lowlands and mountains. 



I have produced Roestclia cornuta on Pyrits Aucuparia by 

 artificial infection with portions of spore-cushions from twigs 

 of juniper, and have observed a mountain ash in closed forest, 

 with abundant Roestclia, directly beneath an overhanging juniper 

 with diseased needles. 



