1908.] 



Rust in Wheat. 



247 



in so stable a condition that they will never " throw back " 

 to the parent forms. An elementary example may illustrate 

 the possibilities now open to the breeder. Given a dwarf 

 marrowfat pea and a tall round seeded pea, from these he 

 can obtain tall marrowfat and dwarf round seeded peas in a 

 perfectly fixed condition in three seasons at the most. 



The details are too complex to describe here,* and we need 

 concern ourselves only with a description of some experiments 

 designed to test the possibility of applying Mendelian principles 

 to the breeding of disease-resisting varieties of wheat. At 

 the outset it was necessary to find varieties already possessing 

 this characteristic. For this purpose a large collection of 

 wheats was obtained from various parts of the world and 

 records were made as to their susceptibility to rust at intervals 

 throughout the growing season. Those varieties which proved 

 liable to rust were rejected, and the remainder were again 

 tested in the following seasons. As a result of these tests 

 some half-dozen varieties have been found amongst the three 

 hundred grown which are either very slightly susceptible or 

 completely immune to the attacks of yellow rust. The most 

 important of these are Einkorn, Little's Anti-mildew, and 

 " Club wheat." Einkorn is said to be a primitive type of 

 wheat . It produces small flat ears, at first sight not unlike those 

 of a small Goldthorpe barley. The grain is not set free from 

 the chaff on thrashing, but the stalk of the ear breaks into 

 fragments much as barley does. In general habit the plant 

 is small and tufted. From the English agriculturist's point 

 of view the variety is obviously worthless as wheat. Little's 

 Anti-mildew is a variety of considerable interest, as it repre- 

 sents one of the first attempts to cultivate a disease-resisting 

 crop. References to the literature of half a century ago show 

 that this wheat was valued because of its capacity of resisting 

 the attacks of rust, then described, as it still frequently is, 

 as " mildew." Although, I believe, practically extinct in 

 most parts of the country, it still survives on a small scale in 

 some parts of the fen country in East Anglia. " Club " wheat 

 is a closely set variety found in a plot of Northern Duluth 

 wheat by Mr. A. E. Humphries. Its local name is unknown 

 to me. 



* For details see " Mendelism," by R. C. Punnett. (Macmillan and Bowes.) 



