Aug. 2 7, 191 7 Puccinia graminis on Cereals and Grasses 467 



lonifera Vasey, Alopecurus genictUatus L-, Anthoxanthum odorahim L., 

 Beckniannia eritcaeformis (h.) Host., Bromus erectus Huds., B. inermis 

 Leyss., Calamagrostis canadensis (Michx.) Beauv., Cynodon dactylon 

 (L.) Pers., Cynosurus cristatus L., Festuca ovina L., F. rubra L., Holcus 

 lanatus h., Koeleria cristata (L.) Pers., Lolium italicum R. Br., L. perenne 

 L/., L. te-mulentum L., Poa tiemoralis L. 



The results obtained by the writers in the main substantiate and 

 extend those previously obtained by Carleton (6, 7) in this country, 

 who says (7, p. 16) — 



(i) that the forms of black stem rust on wheat, barley, Hordeum jubatum, Agropyron 

 tenerum, A. richardsoni, Elymus canadetisis , and E. canadetisis glaucifolius are iden- 

 tical, with the probability that those on Elymus virginicus, E. virginicus muticus, 

 and Holcus lanatus should be included; (2) that the black stem rust of Agropyron 

 occidentale is physiologically distinct from any other. 



The writers were unable to infect Holcus lanatus, although only a 

 limited number of trials were made. Agropyron smithii {A. occidentale) 

 is a very common host for both P. graminis tritici and P. graminis secalis 

 in the upper Mississippi Valley. All the stemrust which the writers 

 found was one of these two forms. 



Eriksson (11, p. 601) gives Triticum vulgare as a host for wheat stem- 

 rust in Sweden, and states that barley, rye, and oats are sometimes 

 weakly infected. The writers' results agree in general, except that 

 barley is a very congenial host for the rust in this country, a fact pre- 

 viously noted by Carleton. Rye is weakly infected in a very character- 

 istic manner. The production of uredinia in dead leaf areas (see pi. 53) 

 is quite characteristic, although small uredinia may be produced without 

 the killing of large areas. Rye is usually hypersensitive to the rust. 

 Oats are infected rarely and with great difficulty. 



Jaczewski (18, p. 353) gives Triticum vulgare as a host and says that 

 Hordeiim -vulgare, Triticum, re pens, T. caninum, Lolium perenne, and 

 Festuca gigantea can be infected, while Secale cereale, A vena sativa, 

 Dactylis glomerata, Bromus inermis, and B. secalinus are immune. 

 However, the writers have been able to infect both Secale cereale and 

 Avena sativa. 



In the spring-wheat-growing States some of the commonest grasses 

 are very susceptible to wheat stemrust. The common species of Agro- 

 pyron, except A . repens, are very congenial hosts. All of the species of 

 Elymus and the closely related Hystrix which were tried are very sus- 

 ceptible, as well as the species of Hordeum. Of the cereals rye may 

 rarely be affected with the rust in the field, and natural infection rarely, 

 if ever, occurs on oats. Barley is very commonly affected, more often, 

 probably, than with rye stemrust, to which it is also susceptible. Bromus 

 tectorum is moderately susceptible, the uredinia usually remaining small 

 and often round. 



Only a few grasses besides the common hosts have been infected in 

 the greenhouse. Oats and two of the grasses which are common hosts 



