THE BASLDIUM FUNGI (BASIDIOMYCETES) 245 



appear as blistery patches, much like those made by the red- 

 dish spores except for the difference in color. The teleuto- 

 spores are scattered over the ground and upon wheat and oat 

 straw. After a period of dormancy, usually lasting through 

 the winter, these spores germinate. From each cell of the 

 teleutospore in the spring there grows a small hypha (Fig. 

 199, D), quite resembling the one which grows from the smut 

 spore (Fig. 196). Similarly, each cell of this hypha may form 

 one of the thin-walled spores (sporidia). 



Puccinia graminis sometimes has another stage in its life 

 cycle. In regions as in the New England States where 

 a shrub known as barberry is common, the sporidia when 

 alighting upon leaves of the barberry may grow and produce 

 within the leaf an extensive growth of mycelium. When 

 this mycelium produces spores they appear in a peculiar cup 

 on the underside of the barberry leaf (Fig. 199, E). These 

 spores being different from any of the three described, and 

 being formed in a cup, are called cecidiospores, or cup spores. 

 ^Ecidiospores may reproduce the rust plant upon wheat and 

 oats. When the life cycle of black rust was first being dis- 

 covered, it was thought that all four stages are necessary, 

 and that if any one stage could be destroyed, the others 

 would of course be destroyed. Therefore attempts were made 

 to kill the barberry plants so that secidiospores could not be 

 formed. About this time it was discovered that the barberry 

 stage can be omitted. Uredospores persist through the winter 

 in sufficient quantity to reproduce the rust upon oats and 

 wheat in the following spring. No satisfactory preventive 

 for this fungus has been discovered. Some progress has been 

 made by learning which varieties of wheat and oats are most 

 resistant to attacks by the parasite. 1 



234. Other rusts. Upon the leaves and stems of carnations 



an injurious rust ( Uromyces caryopJiyllinus) sometimes appears. 



Asparagus rust (Puccinia Asparagi), probably introduced into 



this country from Europe but a few years ago, is now generally 



1 "Rusts of Cereals," Bulletin 109, S. Dak. Agr. Exp. Sta., 1908. 



