Aug. 37. 1917 Pticcinia graminis on Cereals and Grasses 441 



There can be but little question that Agropyron tenerum is very instru- 

 mental in spreading and possibly also in the overwintering of the wheat 

 stemrust and the rye stemrust. It is especially important because it is a 

 congenial host for at least these two common biologic forms and can 

 also be easily infected by P. graminis tritici compacti. 



Table VII. — Results of inoculations with urediniospores from Agrostis alba L. 



The stemrust on Agrostis alba looks somewhat like P. graminis 

 phleipratensis . It infects the cereals in somewhat the same way, and 

 it was at first thought that possibly the rust was P. graminis phleipra- 

 tensis, especially since the urediniospores are nearly equal in size. How- 

 ever, the rust seemed incapable of infecting timothy, and morphologically 

 it differed enough from P. graminis phleipratensis to render any idea of 

 the identity of the two rusts untenable. The rust is no doubt P. graminis 

 agrostis Erikss., since it infects barberry readily. It is capable of infect- 

 ing various grasses and oats, barley, and rye. On the three cereals 

 the infection is very weak and resembles that caused by timothy rust 

 very much. The uredinia were always very distinct, but very small. 

 They were usually about 0.25 mm. in diameter, round or slightly elongate, 

 and were not surrounded by large, dead areas as is so often the case when 

 a biologic form develops slightly on an uncongenial host. From the 

 character of the infection it seems quite improbable that P. graminis 

 agrostis infects any of the cereals in the field, except possibly very 



