200 FUNGI AND FUNGICIDES 



affected part is cut off, causing it to stop growing and 

 lose its green color. As the fungus develops it produces 

 great numbers <>f .-pores, which give ihe pinkish color to 

 the affected parts. As a rule, the di>ease is woix- on 

 weak-growing varieties, and those fields which are sowed 

 latest. Consequently, vigorous growth and early blos- 

 soming are thought to be the chief safeguards against 

 the malady. 



The Wheat Rust 



Pucdnia rubigo-vera 



Probably no disease of cereals causes a greater loss 

 to American farmers than the rust of wheat. It appears 

 to be known wherever wheat is grown, and is often 

 responsible for the destruction of a large percentage of 

 the crop. It has, until recently, been quite generally 

 assumed, by botanists and others, that the fungus caus- 

 ing wheat rust in America is the same species that 

 causes it in Europe a species known to science as Puc- 

 dnia graminis but it has lately been shown that our 

 common rust is often an entirely different fungus, whose 

 Latin name appears above. The European species passes 

 one stage of its existence upon the barberry, causing the 

 familiar cluster-cups, but the other fungus has no con- 

 nection with the barberry. It has a first, or cluster-cup 

 stage, which is passed on certain plants belonging to the 

 Borage family ; and has also two different stages upon 

 wheat. The first of the wheat stages but the second 

 in the life-cycle of the fungus is the red rust stage, 

 called, by botanists, the uredo stage. It is in this con- 

 dition that the fungus is most destructive. Later in 

 the season an entirely different kind of spore is produced 

 the so-called teleuto-spore which forms the third 

 stage of the fungus. But recent investigations have 

 shown that the second, or uredo-stage, is able to survive 



