10 CEREAL RUSTS OF THE UNITED STATES. 



rust is probably the same as our P. rubigo-vera. These authors also 

 make the rust heretofore called P. rubigo-vera simplex, occurring on 

 barley, a distinct species — that is, P. simplex (Kcke.) Eriks. and Henu. 

 (30, p. 260). The writer has no reliable information as to the occur- 

 rence of this species on barley in this country, but what is possibly 

 the same rust has been found occasionally on native species of Hordeum. 



In his inoculation experiments Eriksson also has observed that 

 forms of a certain rust species taken from certain hosts would not 

 infect certain other hosts that are attacked by this same si:)ecies. 

 This may be true even where the hosts are of the same genus. On 

 the other hand, infections will sometimes take place from the host 

 species of one genus to the species of another genus. To such distinct 

 forms of the same rust species he has given the name forma specialis. 

 The form name is taken from the generic name of one of the hosts 

 to which the form is restricted, preceded by the abbreviation f. sp. 

 As there seems to be no good reason why the entire name should not 

 be written as an ordinary trinomial, designating the variety, it will be 

 so written in this bulletin. These forms are, as a rule, as good varie- 

 ties as those established on morphological grounds by phanerogamic 

 botanists. 



Eriksson's researches have led him to conclude that so far as known 

 there are at present ten forms of these cereal rusts in Sweden, that is, 

 three black rusts, Puce in ia graminis secalis on rj^e and barley, P. gram- 

 inis tritici on wheat, and P. graminis avenw on oats; three yellow rusts, 

 P. glumarum secalis on rye, P. glumarum tritici on wheat, and P. glii- 

 mariim hordei on barley; two brown rusts, P. dispersa secalis on rye 

 and P. dispersa tritici on wheat; one dwarf rust, P. simplex on barley; 

 and one crown rust, P. coronifera on oats. The writer's inoculation 

 experiments in 1896 and 1897, several thousmid in number, which will 

 be described in detail further on, showed that there are now at least 

 six distinct forms of cereal rusts in the United States, and probably a 

 seventh, namely, two orange leaf rusts, P. rubigo-vera tritici on wheat 

 and P. rubigo-vera secalis on rye; one crown rust, P. coronata on oats; 

 three black stem rusts, P. graminis tritici on wheat and barley, P. gra- 

 minis secalis on rye, and P. graminis avenw on oats; and one maize 

 rust, P. sorghi on maize. 



In comparing the Swedish and the American rusts, it should be 

 observed that Eriksson uses for the crown rust the name established 

 by Klebahn (42, pp. 134-136), that is, P. coronifera. He justifies this 

 ui)on the basis of his own (28) and upon Klebahn's experiments, which 

 showed that in northern Europe P. coronata Corda is a collective spe- 

 cies, of which one section has Bhamnus cathartica for its ajcidial host 

 and occurs on oats and other grasses, and another section has li.fran- 

 gula for its .Tcidial host, but does not occur on oats. The former is 

 called P. coronifera and the latter is called by the old name P. coronata. 

 Each of these newly made species has also its specialized forms or 

 varieties, there being eleven in all. As the writer has not yet deter- 



