398 THALLOPHYTES 
teleutospore produces a promycelium bearing the basidiospores, 
often called sporidia, as shown in Figure 355. Thus the teleuto- 
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. 
Fic. 355. — Te- Thus four kinds of spores are involved in 
leutospore having the complete life cycle of the Black Rust 
developed the pro- ang g fifth kind occurs. The uredospores 
mycclia bearing : 
basidiospores (s). 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 
