FUNGI 



185 



328. Leaf of barberry with cluster-cups. 



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

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

 (Fig. 328). These orange or yellow eeeidia 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 a?eidiospores are formed in 

 the spring, and after they have been 

 set free some of them lodge on wheat 

 or other grasses, where they germi- 

 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 wedospores ("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 Puecinia 

 graminis produce different spore- 

 forms on different plants. The 

 phenomenon is called hetcroecism, 

 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 

 .j.jQ demonstrated, as has 



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

 wheat rust. j^^^^g ^^ sowing the jecidiospores 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 tbe 

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

 attack various fruit trees oroducing aecidia on their leaves. 



3L'n. Sect 



througli a cluster-cup on 

 barberry leaf. 



