28o 



DIVISION II. — COURSE OF DEVELOPMENT OF FUNGI. 



the outer surface of somewhat cushion-shaped bodies, which are formed by 

 the interweaving of mycelial hyphae immediately beneath the epidermis of the 

 host, more rarely at a greater depth, and burst through it when they form spores. 

 Both are formed acrogenously on crowded sporiferous cells (sterigmata, basidia), 

 which cover the outer surface of the hymenium, either alone or in certain species 

 mixed with or surrounded by paraphyses of peculiar structure ; in a few cases, as the 

 uredo of Melampsora populina, and of Cronartium, they are enclosed in a one-layered 



FIG. 128. Puccinia graminis. .-/ a pair of teleutospores/ germinating with pro 

 mycelium and sporidia sp. /■>' a promycelium with sporidia sj> torn from the spore. 

 C epidermis of the under surface of the leaf of Be rberis vulgaris with a germinating 

 sporidium sf, tin- germ-tube from which has penetrated at 1 into an epidermal cell. 

 l'ispore putting out a germ-tube fourteen hours after being placed on v at< 1 

 Four equatorial Kcrm-pc 1. . >n the empty spore-membrane. C, D magn. 390 



times, A, B somewhat more highly magnified. 



FIG. 1--9. PueciHta Rubigo vera. 



Pair of tcleutospores the lower 

 nil having germinated, the upper 

 germinating! / promycelium, s 

 sporidium. Magn, 390 times. 



envelope like that of the aecidia, the development of which has yet to be more closely 

 examined. 



The uredospores are formed in some species in successive rows and with 

 intervening cells like the aecidiospores, in others singly on slender stalk-like sterigmata, 

 from which they always separate by abscision as they ripen with a view to their 

 dispersion. Their form and structure agree essentially with those of the aecidiospores, 

 Hemileia being the only exception. The teleutospores of most species are formed 



