BSTILAGINK^. 



321 



there grow out small sporidia, which germinate by sending 

 out a slender hypha ; when this hypha comes in contact 

 with the proper host plant, it penetrates the walls of its 



Fig. 234. — TiUetia caries, d, transverse section of an infected wheat-^rain ; e, ripe 

 spore ; /, tlie iir^t stage of germination ; g, the formation of a brandling promyce- 

 lium, with granular protoplaem in its upper end ; A, ihe formation of slender 

 branches winch unite by a Ijind of conjugation ; the ends of these branches give rise 

 somewhat later to very small sporidia, and when thet-e germinate very slend' r hy- 

 phfie are produced, which penetrate the epidermis as at i ; k', mycelium from the 

 young ovary of the wheat — two small lateral branches are shown, from which spores 

 will develop ; k, spores more fully developed.— of, after OErsted ; e-k, after Tulasne, 

 X «0 ; i-*, after Kuhn, x 300. 



cells, and thus gains admittance to its interior, where it pro- 

 duces a new mycelium* (Fig. 224, {). In Ustilago carho the 



* This is upon the authority of Kuhn : " Krankheiten der Culturjre- 

 wacbse," 1859. There are some doubts as to the correctness of his 

 observations, and they have not been confirmed bv any one. 



