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. An-iiiia mtd Pi/rnidia of various species oi Gymnosporangium : 



G. tremclloides 1 and ~, aecidia on leaf of Pyrv.*- .(/>'< ; ." and C, aecidia on leaf 

 of Pijrux Mulus; 10 and 20, portions of the peridiuin of an aecidium from .", 

 showing the peculiar articulation of the cells. 



G. juniperinum ', and l t , aecidia on Pyi-v.x .1 <'<<' [i !'< ; 7 and S, aecidia un 



Aim li'in-li" r i-i'/!i"i-iti. 



G. clavuriii'.i'iii-im and 10, aecidia on Pin c.< /t'tifftlia; 11, I', and /;, aet-idia 

 on C'riitii'iiii* n.i ,111,-nntiM, grown out-of-doors; li,, the same aecidia, enlarged; 

 l.j, !', and 17, aecidia on Crataegus Oxy/ii'/i/il/m, indoor culture ; 18, 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 Sorb us (Pi/rux). Infections with 



