200 



FUXGI AXD FUXGICIDES 



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

 lose its green color. As the fungus develops it produces 

 great numbers of spores, which give the pinkish color to 

 the affected parts. As a rnle^ the disease is worse on 

 weak-growing varieties, and those fields which are sowed 

 latest. Consequently, vigorous growth and early blos- 

 soming are thought to be the chief safegtiards against 

 the malady. 



The Wheat Rust 



Piiccinia ruhigo-vera 



Probably no disease of cereals causes a greater loss 

 to American farmers than the rust of wheat. It rippears 

 to be know^n 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, whose 

 Latin name appears above. The European species passes 

 one stage of its existence ujoon the barberry, causing the 

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

 nection w^ith 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 wdieat stages — btit 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 ftingus 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 ftingus. But recent investigations have 

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



