CRYPTOGAMS 



319 



only the dark teleutospores are produced. These remain on 

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

 the work of reproduction in spring. For this reason the 

 teleutos are popularly known as " winter spores " in contra- 

 distinction to the uredos, or " summer spores," whose activity 

 is confined to the warm months. 



It was formerly supposed that black rust was caused by a 

 different fungus from that producing red rust, and to it the 

 name Puccinia was given. This has been 

 rotained as a general designation for all fungi 

 undergoing these two phases, and the par- 

 ticular form of fungus that we are now con- 

 sidering is known in all its stages as Puccinia 

 graminis. 



361. The nonparasitic stage. — The for- 

 mation of teleutospores completes that por- 

 tion of the life history of the fungus during 

 which it is parasitic on wheat and grasses of 

 different kinds. In spring they begin to 

 germinate on the ground, each cell producing 

 a small filament, from which arise in turn 

 several small branches. Upon the tip of 

 each of these branches is developed a tiny 

 sporelike body called a sporidium (Fig. 454), 

 which continues the generation of the rust ter's "Plant stmc- 

 fungus through the next stage of its exist- 

 ence. The filament which bears these sporidia is not para- 

 sitic, but when the sporidia ripen and the spores contained 

 in them are scattered by the wind, there begins a second 

 parasitic phase, which forms the most curious part of this 

 strange life history. 



362. The aecidium. — Examine next the under side of 

 some barberry leaves (or comfrey, etc., if orange leaf -rust 

 is used) for clusters of small whitish bodies that appear 

 under the lens like little white corollas with yellow anthers 

 in the center, Examine a section of one of these under the 



Fig. 454. — Tclcu- 

 tosporo germinating 

 and forming sporidia, 

 s, s. {From Coul- 



