PLANTS WHICH CAUSE DECAY 405 



to be a distiDct form, though it in every respect closely 

 resembles that of the Wheat, and passes its cluster- 

 cup stage on the Barberry. The same is probably true 

 of the Black Stem Rust of the Rye: it does not appear 

 to affect any other Grain. 



The Orange Leaf Rust of the Wheat is very similar 

 in appearance to the Black Stem Rust; its cluster- cup 

 stage is passed on Anchusa and Echium; the uredo 

 lives over the winter in the United States. The Orange 

 Leaf Rust of the Rye appears to be distinct from that 

 of Wheat: its uredo lives over the winter in the 

 southern states. 



The Crown Rust of Oats is found only on Oats. It 

 resembles the Orange Leaf Rust of Wheat. Its cluster- 

 cup stages are passed on Rhamnus. 



The method of observing the germination of the 

 cluster -cup spores or the uredospores is simply to 

 place perfectly fresh spores in a hanging drop of water. 

 The teleutospores are to be treated in the same manner, 

 only they must be preserved during the winter, for they 

 will germinate only in the spring. These germination 

 experiments may not always succeed, but they are 

 worth trying. 



In order to make infections with uredospores, it is 

 only necessary to grow some Wheat in pots during the 

 summer; and when the leaves are three or four inches 

 long, bring in a fresh leaf of Wheat which is well covered 

 with uredospores, and tie two of the growing Wheat 



