so THE AMERICAN BOTANIST 



mycetes, or sometimes as Aecidiomycetes. There are possibly 

 ten thousand rusts, all parasitic upon various species of green 

 plants and in many cases confined to a single species of hi st 

 plant. One of the most important and interesting facts about 

 them is that a large number require more than one species of 

 plant for the completion of their life cycle. Thus the rust of 

 apple passes part of its existence on the cedar, the corn rust 

 begins life on the oxalis and the wheat rust has one of its 

 stages on the barberry. Some of these rusts have no less than 

 five different kinds. of spores, each in its proper place in the 

 life cycle and each carrying the rust to new areas of infection, 

 all of which shows how powerful for harm some of the 

 species are. 



The botanist knows the wheat rust as Puccinia gramims. 

 Under this name, however, are included at least half a dozen 

 forms, some of which affect wheat, while others injure rye, 

 oats, barley and various wild grasses. It is likely that all may 

 live on the barberry, but unless they happen to be of the right 

 form, they cannot harm the wheat though they may attack other 

 cereals if they be in the vicinity. The rust is especiallv fond 

 i f Agropyron repens, the well-known quick-grass or quack- 

 grass. One might be willing to donate a bushel of wheat now 

 and then, if the rust would only run this pestiferous species 

 out of existence. 



Under favorable conditions, the wheat rust begins its life 

 cycle in spring on the leaves of the barberry. Here the fruit- 

 ing parts form thickened cushion-like growths from one to 

 several times the diameter of a pinhead. Spores from these 

 bodies are blown by the wind to wheat plants in the vicinity 

 and there set up an infection which later manifests itself in 

 rusty patches on the leaves and stems, and greatly reduces 

 their vigor. From the plants on the wheat new spores are 

 given off to set up new infections, and so spread the mischief. 

 Along toward the end of the season, two-celled, dark-colored 

 spores are produced, and these survive the winter and in spring 



