402 



EXPJCBIMJSNTS 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 (I'ed nist stage), of the 

 Black Stem Rust of Wheat. 



. 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- 



■J6 Summer sporei of tlio Black stem Rust 4„™ J.-U„ lonf li\' iiin.inc nf 

 of Wheat. ucrmiuatiiiK "II a Wheat leaf lUg TiUe l(\lt l)\ meaUSOt 

 anil spiiiUng the germ tubes tlirough the , , ^ p 



stomata. a germ-tuue and lorming 



