Aug. 27, 191 7 Puccinia graminis on Cereals and Grasses 



481 



The facts cited above raise an interesting question which the writers 

 have not yet been able to answer — namely, Is P. graminis avenae a 

 plastic form or is it a composite form from which the component forms 

 can be isolated by culture on various hosts? Morphological studies of 

 the stemrust of oats made by Mr. M. N. Levine, of this Station, not 

 yet published, show that P. graminis avenae is very variable morpho- 

 logically, more variable than any of the other biologic fonns. Spores 

 practically indistinguishable from those of P. phleipratensis , and others 

 very similar to those of P. graminis agrostis, are commonly produced 

 by P. graminis avenae. The infection capabilities of the three rusts are 

 similar. These facts may be of some significance, but, at present, spec- 

 ulation only is possible. 



Stemrust of oats was found very commonly in the region covered by 

 the survey. It was very prevalent on grasses in the western mountain 

 valleys, and, on account of the large number of possible hosts, it is quite 

 probable that grasses are quite important in its spread and possibly as 

 a means of its overwintering. Unfortunately no studies on this phase 

 of the problem have yet been made. They are highly important and 

 will be made as soon as possible. 



Table XXXII. — Results of inoculations with uredinios pores of P. graminis phleipra- 

 tensis 



Original host. 



Immediate host. 



PJant inoculated. 



Re- Degree of in- 

 sult, feclion. 



Phlcum pratensc. . 

 Festuca elatior. . . . 



Do 



Do 



Do 



Phleum pretense.. 



Do 



Do 



Festuca elatior. . . . 



Do 



Festuca pratensis . 

 Festuca elatior. . . . 



Do 



Do 



Do 



Phleum pratense. 



do 



do 



do 



Avena sativa 



Phleum pratense. 



do 



do 



do 



do 



Hordeum vulgar e. 



Phleum, pratense. 



....do 



....do 



....do 



Agrostis alba 



Alopecurus geniculaius . 

 Alopecurus pratensis. . . 



Avena sativa 



do 



Festuca elatior 



Festuca ovina 



Festuca rubra 



Holcus lanaius 



Hordeum. vulgar e 



do 



Koeleria crislata 



Poa compressa 



Secale cereale 



Triticum, vulgare 



lbs 

 70 



Moderate. 



Moderate to 



heavy. 



Weak. 

 Heavy. 



Moderate. 



Weak. 

 Heavy. 



