CEREAL IMPROVEMENT SELECTION 191 



kept constantly free from foreign plants and weeds. It 

 will be one or more acres in size, depending upon the 

 acreage of field crop grown. 



192. Pure-line selection. Individual or pure-line 

 selection is selection from a single, superior, mother plant, 

 which plant and its progeny are kept protected from out- 

 side pollination. The latter is not difficult in any of the 

 small cereals except rye. This method of selection was 

 practiced by H. Vilmorin at Verrieres, France, and has 

 been called the Vilmorin System of selection. Later at 

 Svalof, Sweden, it has been referred to usually as the 

 System of Pedigree Culture. The basic principle of the 

 system is to separate from a commercial variety the 

 greatest possible number of forms, to propagate each of 

 these separately, and finally through a process of elimi- 

 nation to isolate a few of the best for increase and distri- 

 bution. 



193. Work of Le Couteur. The method of form- 

 separation, in German " Formentrennung " (Friiwirth), 

 was long ago employed as a means of discovering superior 

 individuals, as a starting point in developing new strains, 

 by an English breeder, Le Couteur (1837, p. 119), at 

 Bellevue, on the island of Jersey, in the early part of the 

 last century. La Gasca, of the University of Madrid, 

 showed Le Couteur that his grain was a composite of 

 many distinct types, and not pure, as he supposed. Le 

 Couteur therefore saved spikes of 23 types indicated and 

 sowed the kernels of each spike separately. Some of 

 the types were found to be poorer and some better than 

 the average of the parent variety. New varieties were 

 isolated in this way and put on the market. One of 

 them is yet grown considerably in western Europe, and 

 is said to be a pure and uniform type. It was isolated 



