390 



UREDINEAE. 



In May or June the cushions swell up and become large 

 brownish-yellow gelatinous clumps, dotted over with dark points, 

 the teleutospores. Promycelia arise from one or more germ- 

 pores in each spore, and give off basidia with sporidia (basidio- 



FiG. 224. — Aecidia and Pycnidia of various species of Gyninosporangium : 



G. tremetloides — 1 and S, aecidia on leaf of Pyrvs Ai-ia ; 5 and 6, aecidia on leaf 

 of Pyrus Mains ; 19 and 20, portions of the peridium of an aecidium from 5, 

 showing the peculiar articulation of the cells. 



G. junipm-inum — 3 and U, aecidia on Pjp-us Aucujparia ; 7 and S, aecidia on 

 Amdanckier vulgaris. 



G. clavariacfomie — 9 and 10, aecidia on Pyius latifolia', 11, IS, and 16, aecidia 

 on Crataegus Oxyacantha, grown out-of-doors ; lU, the same aecidia, enlarged ; 

 13, 15, and 17, aecidia on Crataegus Oxyacantha, indoor culture ; IS, deformed 

 twig of Crataegus bearing pycnidia. (After Tubeuf.) 



spores) capable of immediate germination. The gelatinous mass 

 dries up from time to time, leaving a bright yellow scar on 

 the swollen part of the host-branch. The sporidia germinate 

 most easily on species of Sorhus {Pyrus). Infections with 



