402 



EXPERIMENTS WITH PLANTS 



spores), as shown in Fig. 225. These two forms of 

 spores are developed from the same mycelium, the one 



224, Summer spores, or uredo- 

 spores (red rust stage), of the 

 Black Stem Rust of Wheat. 



225. Autumn spores, or teleuto- 

 spores (black rust stage) , of the 

 Black Stem Rust of Wheat. 



(uredospores) earlier, the other (teleutospores) , later 

 in the season. The uredospores germinate during the 

 summer; they send out germ-tubes which enter the 

 stomata of the leaf (Fig. 226). The teleutospores rest 



during the winter; in the 

 spring they germinate, 

 producing conidia (Fig. 

 227, c) , which are borne by 

 the wind to the leaves of 

 the Barberry plant; here 

 they germinate, penetrat- 



226. Summer spores of the Black Stem Rust * ^ fVio Incif Kat TvioQna r^f 

 of Wheat, germinating on a Wheat leaf ^^& ^^'^^ ^^"^^ ^V UieaUb OL 

 and sending the germ tubes through the , , in 



stomata. a gcrm-tube and forming 



