280 FUNGI 



hours and form new mycelia, from which, in six to ten 

 days, fresh spores arise. Formerly this was thought to 

 complete the life history of the fungus, to 

 which the name of Uredo was given. It is 

 now known, however, that the red rust is 

 merely a stage in the life cycle of the plant, 

 and to this stage the old name uredo is 

 applied, and the spores are called uredo- 

 spores. 



400. Black Rust. Next examine with 

 your lens a part of the plant attacked by 

 black rust. Do you observe any difference 

 except in the color ? Do the two kinds of 

 rust attack all parts of the plant equally ? 

 If not, what part does each seem to affect 

 more particularly ? At what 

 S' 537 season does the black rust ap- 



536,537. Leaf pear most abundantly? 

 *,h "S ^ i formerly supposed that 

 rust, Puccinia ru- black rust was caused by a 

 stage^e upper different fungus from that pro- 

 side of leaf; 537, ducing red rust, and to it the 



under side. ,_, . . . , 



name Pucctnia was given, but 

 it is now known to be only another phase of 

 the same parasite that produces the red rust. 



TM. T> -,. j i 538. Stalk 



The name Puccinia is retained as a general w j tn p vc cmia 

 designation for all fungi undergoing these two graminis, te- 

 phases, and the particular form of fungus that 

 we are now considering is known in all its stages as Puc- 

 cinia graminis. 



401. Teleutospores. Toward the end of summer the 

 same mycelium that bore the uredospores begins to 

 develop the dark spore clusters that give to black rust its 

 characteristic color and its name. After this the uredo- 

 spores soon cease to be developed at all, and only the dark 

 ones called teleutospores are produced. These remain on 

 the culms in the stubble fields over winter, ready to begin 



