170 



BOTANY. 



parasite, and at length burst through the epidermis (Fig. 

 94, A and I). The oonidia quickly drop out and are car- 



FiG. 94. — Wheat-nist (Puccinia graminis). I, a cross-section of a Barberry- 

 leaf through a mass of Cluster-cups; a, a, a, cups opened and slieddingr their 

 conidia; p, and A, above, cu^s not yet opened; sp, sp, spermogones which pro- 

 duce spermatia, whose function is not Icnown. ii, three Red-rust spores, ttr, on 

 stalks : t, a Black -rust spore. 7/J, a mass of Black-rust spores bursting through 

 the epidermis, e, of a leaf. All highly magnified. 



ried away by the -vraids. 

 cluster-cup stage. 



This stage is known as the 



