280 DIVISION IL.—-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. Puccınia graminis. A a pair of teleutospores ¢ germinating with pro- FIG. 129. Pugeinia Rubiyo vera. 
mycelium and sporidia sf. 3 a promycelium with sporidia sf torn from the spore. Pair of teleutospores, the lower 
C epidermis of the under surface of the leaf of Berderis vulgaris with a germinating not having germinated, the upper 
sporidium sf, the germ-tube from which has penetrated at z into an epidermal cell. inating; 2 p ycelium, s 
D uredospore putting out a germ-tube fourteen hours after being placed on water. sporidium, Magn. 390 times. 
Four equatorial germ-pores are seen on the empty spore-membrane, C, D magn. 390 
times, 4, B somewhat more highly magnified. 
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 
