70 Rusts. (cH. 
Puccinia glumarum. 
This species, known as yellow rust, is the commonest 
form of rust found in this country. It may be readily 
distinguished from Puccinia graminis by the uredospore 
stage. In this case the uredo patches or sori are orange 
yellow instead of dark orange coloured as in Puccinia 
graminis and most of the other rusts. The sori are 
smaller and are often united with their fellows, making 
them appear as lines on the leaf and stem; they are 
usually present in larger numbers. The uredospores 
themselves are more rounded, but otherwise they are 
very similar. The teleutospores are produced in smaller 
sori, and the deep gaping wounds of Puccinia graminis 
are never present. They are also much shorter and 
appear more like black dots than lines. 
No aecidiospore stage has been found and no 
alternate host. The uredospores and teleutospores 
germinate in a similar manner to those of Puccinia 
graminis, and the uredospores probably carry on the 
disease from one season to another. The yellow rust 
of wheat cannot be distinguished from the yellow rust 
of barley under the microscope, but by experimenting 
it has been found that barley cannot be attacked by 
yellow rust of wheat, neither can wheat be attacked 
-by yellow rust of barley. From our point of view this 
fungus may be divided up into a number of species 
each of which has its particular host or hosts. 
There are numerous other rusts besides the two 
described, some of which possess all the spore stages 
and others only one or some of the stages; the differ- 
ences are very similar to those of the two species 
described. 
