THE BASIDIUM 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, Z>), 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. 

 jEcidiospores may reproduce the rust plant upon wheat 

 and oats. When the life cycle of black rust was discovered, 

 it was thought that all four stages are essential to it. It is 

 now known, however, that the barberry stage may sometimes 

 be omitted. The native barberry, not the Japanese variety, 

 is the one on which this rust grows, and efforts are being 

 made to destroy this plant with the hope of reducing the 

 rust disease on wheat and oats. Uredospores persist through 

 the winter in sufficient quantity to reproduce the rust upon 

 oats and wheat in the following spring. No satisfactory pre- 

 ventive 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 caryophyllinus) 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 



