358 BROOKLYN BOTANIC GARDEN MEMOIRS 



and rye (Secale cereale) as hosts for the same specialized race Secalis. 

 Carleton, on the other hand, places wheat and barley as common hosts 

 for the race Tritici, although he gives no information regarding the 

 relation of the rye rust to the other forms. Other variations in the 

 hosts for the different races, as reported by these three workers, also 

 occur. Eriksson lists Dactylis glomerata as a host for the race Avenae; 

 Jaczewski lists it for the race Secalis; and Carleton records it as a 

 host for both races Avenae and Tritici. Agropyron repens is a host for 

 the two races Secalis and Tritici according to Jaczewski. Carleton 

 records the race Avenae on Hordeum murinum, while Eriksson places 

 this host, along with the other species of Hordeum, as a host for the 

 race Secalis. 



It is important to note that many grasses are listed by Stakman 

 and Piemeisel as common hosts for several races. They suggest that 

 the six races which they experimented with may be divided into two 

 groups on the basis of their parasitism. The races Tritici, Tritici 

 compacti and Secalis form one group ; these vary in their capacity for 

 infecting certain hosts but all three vigorously infect Agropyron 

 cristatum, A. elongatum, A. smithii, Bromus tectorum, Hordeum jubatum, 

 H. vulgare, Elymus canadensis and Hystrix patula. The other three 

 races, Agrostis, Avenae and Phleipratensis , also vary in their infecting 

 capacity but all vigorously attack Alopecurus geniculatiis , A. pratensis, 

 Dactylis glomerata, Holcus lanatus and Koeleria cristata. Three hosts, 

 Bromus tectorum, Hordeum vulgare and Secale cereale, are infected by 

 all six races. 



Stakman and Piemeisel do not regard the barley rust as a distinct 

 race. Barley is a very favorable host for races Secalis, Tritici, and 

 Tritici compacti, as well as being susceptible to the other three races. 

 In the field barley seems especially to harbor the race Tritici. 



Freeman and Johnson (57) have confined their work almost ex- 

 clusively to the cereal hosts of Puccinia graminis. They conclude 

 that their experiments indicate the existence of four specialized races : 

 Tritici on wheat, Hordei on barley, Secalis on rye, and Avenae on oats. 

 The rust on wheat can be transferred to barley and rye, but not to 

 oats; the rust on barley can be transferred to the other three cereals, 

 rye, oats and wheat; the rust on rye can be transferred to barley, but 

 not to wheat nor oats ; the rust on oats can be transferred to barley. 

 These workers also report that Hordeum jubatum can be infected with 

 the rust of both wheat and barley; Agropyron repens with the rust of 

 wheat; and Dactylis glomerata with the rust of oats. So far as the 

 cereals are concerned it appears that the different grains may be 

 hosts for more than one specialized race of the black-stem rust. Stak- 

 man and Piemeisel, however, do not regard Hordei as distinct from 

 Tritici. 



