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 
compactt 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 geniculatus, 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 
Tritict compacti, as well as being susceptible to the other three races. 
In the field barley seems especially to harbor the race T7itict. 
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: 
Tritict 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 therust 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 
Tritict. 
