398 



THALLOPHYTES 



teleospore produces a promycelium bearing the basidiospores, 

 often called sporidia, as shown in Figure 355. Thus the teleo- 

 spore occupies the same position in the life history of Rusts as the 

 brand spore occupies in the life history of Smuts. The basidio- 

 spores are scattered by the wind, and in regions where Barberry 

 bushes grow, they come in contact with the leaves of the Barberry 

 where they grow and produce myceha in the leaf tissues. 

 Upon the Barberry, the mycelia produce on 

 the under surface of the leaf small cups called 

 aecia in which spores are borne in chains 

 as shown in Figure 356. These spores are 

 called aeciospores or cup spores. The 

 aeciospores, which are shed in the spring 

 or early summer, are disseminated by the 

 wind and start the disease on the grains or 

 other Grasses, thus completing the life cycle 

 as it is shown in Figure 357. 



In connection with the development of the 

 aeciospores there occur on the upper sur- 

 face of the Barberry leaf very small flask- 

 shaped cups called pycnia, in which are pro- 

 duced very small spores called spermatia or 

 pycniospores. The pycniospores have no func- 

 tion and the pycnia and aecia are supposed to 

 represent the remnants of a sexual apparatus 

 which has become functionless. 



Thus four kinds of spores are involved in 

 the complete life cycle of the Black Rust 

 and a fifth kind occurs. The urediniospores 

 and teleospores occur on the grains or other 

 Grasses. The basidiospores are produced by 

 the teleospores and no host is required, while aeciospores occur 

 on the Barberry bush. 



If the Black Rust must have all of the stages in order to 

 propagate from year to year, then it seems that there should be 

 httle or no Black Rust in regions where there are no Barberry 

 bushes, but such is not the case, for the Black Rust occurs 

 abundantly in fields many miles away from Barberry bushes. 

 Just how it gets started on the grains in localities where there 

 are no Barberry bushes is not definitely known. It was once 



Fig. 355. — Tel- 

 eospore having de- 

 veloped the pro- 

 mycelia bearing 

 basidiospores (s). 



