292 THE BREEDING OF ANIMALS 



276. Vilmorin v s pure line wheat-breeding. A good 

 example of the pure line theory among plants is to be 

 found in the very practical and meritorious work of 

 Louis de Vilmorin, who began the improvement of com- 

 mercial varieties of wheat in France about 1840. Vil- 

 morin carefully selected a single head of outstanding merit 

 and from this by in-breeding established a pure line or 

 variety which has bred true to the original ear or head. 

 The commercial seed offered by Vilmorin was always 

 descended from a single plant. Selection in this case 

 failed to bring about any improvement over the original 

 plant, as shown by the Hagadoorns. 1 



" In 1911 Mr. Meunissier, the genetist of the firm of 

 Vilmorin, found the collection of original ears of the varie- 

 ties with which Louis de Vilmorin half a century back 

 began his living museum. Some of these wheats are 

 from the harvest of 1843, others date from 1850, or inter- 

 mediate dates. Mr. Meunissier chose three dozen ears 

 of varieties which are still in the collection, and which 

 have therefore been bred continuously as pure lines for 

 about fifty years. We compared these ears to ears of 

 the 1911 harvest, and photographed them side by side. 

 Some of these pairs x of ears are here shown, each pair con- 

 sisting of the old ear, and its descendant, half a century 

 later. All these generations of selection have not changed 

 any one of the varieties one little bit. It can therefore 

 safely be concluded from this series of experiments, that 

 selection can have no effect, in material pure for its 

 genetic factors. Genetic factors are constant." 



277. Selection most useful when genetic factors are 

 not pure. The pure line theory explains why any 



1 Mrs. C. and Dr. A. L. Hagadoorn, "Selection in Pure Lines," 

 American Breeder's Magazine, 1913, p. 165. 



