404 



EXPERIMENTS WITH PLANTS 



Wheat was more affected with Rust when it stood on 

 the leeward side of a Barberry bush; it was accord- 

 ingly decreed by the Massachusetts Barberry Law of 

 1755 that the Barberry bushes should be destroyed. 



The matter was 

 (>^ ^_ afterward taken 



^'>^;;^A up by botanists, 



who traced the 

 connection care- 

 fully and came 

 to the conclu- 

 sion that the 

 cluster -cup was 

 a necessary 

 stage in the life- 

 history of the 

 fungus. A diffi- 

 culty arose in the fact that the Rust prospers even 

 when there are no Barberry bushes, and it is now 

 known that, in some cases at least (e. g., in Australia), 

 the uredospores can live through the winter and infect 

 the Wheat again in the spring. It is supposed, how- 

 ever, that the teleutospores cannot infect Wheat, but 

 only Barberry. 



The uredospores of the Black Stem Rust of the 

 Wheat readily infect Barley, and vice versa; but it 

 seems highly probable that they cannot infect Oats 

 (nor vice versa) . The Black Stem Rust of Oats seems 



229. Cluster-cup (tecidium) of Black Stem Rust of Wheat. 



