EUTHALLEPHYTA EUMYCETES RUSTS 



225 



Fig. 62. Some Rusts. A, B. D. E. 

 Puccinia graminis. A. Aecidium or 

 Cluster-cup on Barberry; a aecidium, 

 s spermogonia on upper surface. B. 

 Uredo spores; u one-celled, teleuto- 

 spores two-celled. C. Germination of 

 uredospores showing long tube. D. 

 Connection of stem showing two-celled 

 teleutosppres. E. A teleutospore 

 germinating with promycelial tube (/>) 

 and sporidia O/>). F. Two-celled 

 teleutospores of Puccinia coronata on 

 oat leaf. G. Teleutospores of Phrag- 

 midium incrassatum. All much en- 

 larged. A and G after I/uerssen. B- 

 D after DeBary. E) after Tulasne. 



spermogonial stage; the flask-shaped bodies are called spermogonia and contain 

 the spermatia which do not germinate; their function is not known. A sweetish 

 fluid, which attracts insects, is frequently found in connection with these. 

 Directly opposite the flask-shaped bodies are small globular affairs, "cups," 

 (aecidia), slightly irregular on the margins. Owing to their upward growth 

 they rupture the epidermal cells, and finally the lining layer of cells of the cups 

 also breaks, thus exposing a large number of 1 -celled spores borne in chains. 

 These spores arise from short stalks contained at the base of these cups; the 

 cluster cup spores are known as aecidiospores and are transported by the wind 

 and other agencies, and have the power to germinate soon after maturity. When 

 the proper host a grass, such as bent grass, oats or wheat appears, the germ 



