STUDIES IN CRYPTOGAMS 



193 



each producing a short branch with a little spo- 

 ridium, s. 



A most remarkable circumstance in the life 

 history of the wheat rust is the fact that the my- 

 celium produced by the sporidium can live only 

 in barberry leaves, and it follows that if no bar- 

 berry bushes are in the neighborhood the sporidia 

 finally perish. Those which happen to lodge on 

 a barberry bush germinate immediately, produc- 

 ing a mycelium that enters the barberry leaf and 

 grows within its tissues. Very soon the fungus 

 produces a new kind of spores on the barberry 

 leaves. These are called ctcidiospores. They are 

 formed in long chains in little fringed cups, or 

 (Kcidia, which appear in groups on the lower side 

 of the leaf (Fig. 283). These orange or yellow 

 secidia are termed cluster-cups. In Fig. 284 is 

 shown a cross-section of one of the cups, outlin- 

 ing the long chains of spores, and the mycelium in the tissues. 



The aecidiospores are formed in the spring, and after they have 

 been set free, some of them lodge on wheat or other grasses, 

 where they germinate immediately. The germ-tube enters the 



FIG. 282. GER- 

 MINATING TE- 

 LEUTOSPORE 

 OF WHEAT 

 RUST. 



FIG. 283. LEAF 

 OF BARBERRY 

 WITH CLUS- 

 TER-CUPS. 



FIG. 284. SECTION THROUGH A 

 CLUSTER-CUP ON BARBERRY LEAF. 



leaf through a stomate, whence it spreads among the cells of the 

 wheat plant. In summer one-celled reddish uredospores ("blight 

 spores," red-rust stage) are produced in a manner similar to the 

 teleutospores. These are capable of germinating immediately, 



