Observations and Experiments on Cereal Rusts. 173 
zation is not quite so fixed as far as black rust is concerned. 
Barley, as has already been pointed out by Stakman and 
Piemeisel, is infected by all the six forms that these authors 
have worked with. Again rye has been reported in other regions 
to be infected by the form on wheat. In this locality wheat has 
been repeatedly infected with the form on Couch grass. It seems 
likely that in every class of cereals there are certain varieties, 
which are undoubtedly susceptible to one or more biologic 
forms of this rust, other than the one to which they are said 
to be restricted. Probably the differences in specialization re- 
corded from different regions are largely due to the fact that the 
various investigators have been working with different varieties. 
To illustrate this fact one may say that some more susceptible 
variety of rye may be infected by the form on wheat in this 
locality. Again the variety of wheat (Red Sudan) may be infected 
by the form on rye or Couch grass in other countries too. 
Brown rust of wheat (P. triticina Evikss. and Henn.). 
Eriksson* has found that this form can sometimes infect rye. 
The writer made some inoculations with a pure culture on wheat, 
rye, barley and Agropyron repens. Barley and Agropyron repens 
were not infected, wheat showed very good infection and out 
of twenty-one seedlings of rye three were infected. The results 
are thus in complete agreement with those of Eriksson as regards 
the casual infection of rye with the brown rust of wheat. 
Brown rust of rye (P. dispersa f. sp. secalis 
Evrikss. and Henn.). 
This form has been found by Eriksson* to be altogether 
specialized on rye. The same has been found to be true in this 
locality. Inoculations with a pure culture were made in August 
Ig21, and in both the trials it was found that barley, wheat 
(Red Sudan) and Agropyron repens were not infected, whereas 
rye inoculated on both occasions showed heavy infection. 
The dwarf brown rust of barley (P. simplex Erikss. and Henn.). 
Some inoculations were made in August 192I with a pure 
culture of this rust, on wheat (Red Sudan), rye, Agvopyron 
vepens and barley; only barley was infected. This rust too 
seems therefore to be quite specialized. 
Yellow Rust. 
In this rust also there is strict specialization of the different 
biologic forms as pointed out by Eriksson}. The writer 
* Eriksson, J., Ann. Sc. Nat. sér. 8, Ix, p. 241 (1899). 
t Eriksson, J., Ber. Deutsch. Bot. Gesell. x11, p. 292 (1894). 
