512 THE SMALL GRAINS 



to employ them in breeding, promises at present to be the 

 best means of avoiding damage by rust. Just what this 

 resistance is has not yet been satisfactorily determined, 

 but Ward, Biffen (1907-08 b), and Stakman (1914) 



FIG. 157. Resistance of durum wheat (a) to rust, compared with 

 common wheat (6). 



maintain that external morphologic characters have little 

 or nothing to do with it. Biochemic investigations are 

 needed in connection with this question. 



Some of the existing wheat varieties which already have 

 been found to be strongly resistant to rust are Khapli 



