FUNGI 



185 



called cecidiospores. They are formed in long chains in little fringed 

 cups, or cecidia, which appear in groups on the lower side of the leaf 

 (Fig. 328). These orange or yellow secidia are termed cluster- cups. 

 In Fig. 329 is shown a cross-section of one of the cups, outlining- 



the long chains of spores, and the 

 mycelium in the tissues. 



The secidiospores are formed in 

 the spring, and after they have been 

 set free some of them lodge on wheat 

 or other grasses, where they germi- 



328. Leaf of barberry with cluster-cups. nate immediately. The germ-tube 



enters the leaf through a stomate, 



whence it spreads among the cells of the wheat plant. During sum- 

 mer one-celled uredospores ("blight spores") are produced in a man- 

 ner similar to the teleutospores. These are capable of germinating 

 immediately and serve to disseminate the fungus during the summer 

 on other wheat plants or grasses (Fig. 330). Late in the season, 

 teleutospores are again produced, 

 completing the life cycle of the 

 plant. 



Many rusts beside Puccinia 

 graminis produce different spore - 

 forms on different plants. The 

 phenomenon is called hetercecism, 

 and was first shown to exist in 

 the wheat rust. Curiously enough, 

 the peasants of Europe had ob- 

 served and asserted that barberry 

 bushes cause wheat to blight long 

 before science explained the rela- 

 tion between the cluster-cups on 



barberry and the rust 



on wheat. The true 



relation was actually 

 330 demonstrated, as has 



329. Section through a cluster-cup on 

 barberry leaf. 



Uredospores of since been done for many other rusts on their respective 

 wheat rust. h os t s fty sowing the cseidiospores on healthy wheat 

 plants and thus producing the rust. The cedar apple is another rust, 

 producing the curious swellings often found on the branches of red 

 cedar trees. In the spring the teleutospores ooze out from the 

 " apple " in brownish yellow masses. It has been found that these 

 attack various fruit trees producing rocidia on their leaves. 



