170 BOTANY. 
parasite, and at length burst through the epidermis (Fig. 
94, A and 7). The conidia quickly drop out and are car- 
Fie. 94.—Wheat-rust (Puccinia graminis). J, a cross-section of a Barberry- 
leaf through a mass of Cluster-cups; a, @, a, cups opened and shedding their 
conidia; p, and A, above, cups not yet opened; ia sp, spermogones which pro- 
duce spermatia, whose function is not known. , three Red-rust spores, ur, on 
stalks; ¢,a Black-rust spore. JIJ,a massof Black-rust spores bursting through 
the epidermis, e, of a leaf. All highly magnified. 
ried away by the winds, This stage is known as the 
cluster-cup stage, 
