HEMIBASIDIOMYCETES 



333 



twelve germ-pores, and are produced singly at the tips of 

 unbranched hyphae ; these hyphae are produced in dense 

 clusters just below the epidermis, which is finally ruptured, 

 exposing the sorus or dense aggregation of uredospores. 



FIG. 96. Phragmidium rnbi-idaei, a parasite on rasp- 

 berry leaves, i, under surface of a raspberry leaflet showing 

 numerous sori of teleutospores ; 2, teleutospore ; 3, section 

 through an aecidium ; a, chains of spores ; b, b, large sterile 

 cells or paraphyses forming the covering of the aecidiospores ; 

 4, uredospores. Fig. i, nat size ; remainder mag. 



The sori of uredospores become exposed in all known 

 instances, excepting the genus Hemileia, by rupturing the 

 epidermis. In Hemileia the hyphae bearing the uredo- 

 spores and later the teleutospores emerge in small 

 clusters through the stomata. 



