398 



THALLOPHYTES 



tcleutospore produces a promycelium bearing the basidiospores, 

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

 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 mycelia in the leaf tissues. 

 Upon the Barberry, the mycelia produce on 

 the under surface of the leaf small cups called 

 aecidia in which spores are borne in chains 

 as shown in Figure 356. These spores are 

 called aecidiospores or cup spores. The 

 aecidiospores, 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 

 aecidiospores there occur on the upper sur- 

 face of the Barberry leaf very small flask- 

 shaped cups called spermagonia, in which are 

 produced very small spores called spermatia 

 or pycniospores. The spermatia have no 

 function and the spermagonia and aecidia 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 uredospores 

 and teleutospores occur on the grains or 

 other Grasses. The basidiospores are pro- 

 duced by the teleutospores and no host is required, while aecidio- 

 spores 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 

 little 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. — Tc- 

 leutospore having 

 developed the pro- 

 mycelia bearing 

 basidiospores (s). 



