382 



THE FUNGI WHICH CAUSE PLANT DISEASE 



Spores mostly round or ovate, echinulate, with three or four germ 

 pores, yellow, 20-30 x 17-24 /i. 



III. Telia small, oval, or linear, black, covered by epidermis, 

 surrounded by a thick bed of brown paraphyses. Spores ob- 

 long or elongate, cimeiform, slightly constricted, the lower cell 

 generally attenuated, apex thickened, truncate or often obliquely 

 conical. Spores smooth, brown, variable in size^ 40-60 x 15-20 /*• 

 Pedicels short. 



Hetercecious; and I on Boraginacese. 



II and III on rye. The teliospores germinate as soon as mature. 



Fig. 275.- 



-P. rubigo-vera, section of uredinium. 

 After Bolley. 



P. triticina Erik, is the most common and widely distributed 

 of all rusts of the United States and is a serious wheat pest in 

 India.^* It ordinarily shows only the uredinial stage. The telio- 

 spores germinate the following spring after a resting period. 



Coextensive with wheat culture.'"* Epidemics are frequent. 



Bolley *■ '• " (see also '**) has shown it capable of hibernation by 

 urediniospores and by live winter mycelium and it has further been 

 shown that the spores themselves can survive freezing in ice. The 

 aecial stage can be entirely omitted. 



This species is combined with P. triticina by Garleton ^^* and 

 treated as two races. The name P. dispersa is also used to 

 cover the same two species. P. rubigo-vera tritici on wheat and 

 P. rubigo-vera secalis on rye. 



