506 THE SMALL GRAINS 



Eriksson and Henning (1894) and the author (Hitchcock 

 and Carleton, 1894, pp. 2-4) began investigations, after- 

 wards continued by others, which showed the existence 

 of distinct physiological forms of this and other cereal and 

 grass rusts. The separate forms of this rust on cereals in 

 this country are the orange leaf -rust of wheat (Puccinia 

 rubigo-vera tritici, Carleton) and the orange leaf -rust of 

 rye (P. rubigo-vera secalis, Carleton). In Europe the name 

 brown rust (P. triticina, Eriks. & Henn.) is given to this 

 last-named species, though in this country the uredospore 

 stage is not brown. The different physiologic forms 

 will not be discussed here separately. They present no 

 morphologic differences, but are important from the 

 standpoint of propagation of the species. The form on 

 rye will not infect wheat, and the form on wheat will not 

 infect rye. 



The fact that the rusts have four different stages, corresponding 

 to the different stages of insects, probably needs no discussion in 

 detail, except to call to mind that the different stages are not al- 

 ways on the same host plant, and that one or more of the stages are 

 sometimes wanting. The secidial stage of this leaf-rust occurs in 

 Europe on species of the borage family of plants (Anchusa arvensis 

 and other species). In this country no secidial host has yet been 

 found. The rust occurs by far the most abundantly in the uredo or 

 summer rust stage, and is usually more abundant on wheat than on 

 rye. It sometimes covers the leaves with bright orange sori. To- 

 ward harvest time the teleutospores appear in much smaller numbers 

 on all parts of the plant, but particularly the leaves and sheath. 

 The teleutosori show dimly underneath the epidermis, through 

 which they burst sometimes only in a few places. 



This is the rust that is always present, and is sometimes 

 the only one occurring during the season in 'certain local- 

 ities. When unusually abundant, it is likely to cause 

 some damage, by preventing the complete functioning 



