200 FUJfGI AND FUNGICIDES 



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

 lose its green color. As the fungus develops it j^roduces 

 great numbers of spores, which give the pinkish color to 

 the affected ^larts. As a rule, the disease is worse on 

 WTak-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 maladv. 



The Wheat Rust 



Puccinia ruhigo-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- 

 cinia graminis — but it has lately been shown that our 

 common rust is often an entirely different fungus, w^hose 

 Latin name appears above. The European sjoecies 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, bv botanists, the uredo staire. 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 



