ON THE SMALL GRAINS 



Partly in this way, and partly perhaps through 

 accidental development in regions where the rust 

 does not prevail, some varieties of wheat have 

 been introduced that show a large measure of im- 

 munity to the disease. But unfortunately these for 

 the most part have been plants that did not pro- 

 duce grain of very good quality. In general the 

 favorite wheats of the world have remained sub- 

 ject to the attacks of the fungus. Their degree of 

 immunity in any given season has depended upon 

 accidental conditions of weather that interfered 

 with the development or spread of spores of the 

 rust fungus rather than upon any inherent resist- 

 ance of the cereal itself. 



Thus it is familiar experience everywhere that 

 the farmer cannot have any full assurance as to 

 the amount of his grain crop until the grain 

 approaches the ripening stage; because at any time 

 the invisible spores of the rust may sweep as a 

 devastating horde across his fields and, finding 

 lodgement on the grain stalks, so devitalize them 

 as greatly to reduce their capacity for seed 

 formation. 



The attempt has been made many times to esti- 

 mate the average loss that results to the grain 

 growers of the world — and hence, of course, ulti- 

 mately to the consumers in every rank of life — 

 from the attacks of this microscgpic but all-pow- 



[51] 



