Breeding of Cereals 79 



Few of the varieties of wheat show conspicuous differences, 

 although their number is great. If we compare the differentiating 

 characters of the smaller types of cereals with those of ordinary 

 wild species, even within the same genus or family, they are obviously 

 much less marked. All these small characters, however, are strictly 

 inherited, and this fact makes it very probable that the less obvious 

 constituents of the mixtures in ordinary fields must be constant and 

 pure as long as they do not intercross. Natural crossing is in most 

 cereals a phenomenon of rare occurrence, common enough to admit of 

 the production of all possible hybrid combinations, but requiring the 

 lapse of a long series of years to reach its full effect. 



Darwin laid great stress on this high amount of variability in the 

 plants of the same variety, and illustrated it by the experience of 

 Colonel Le Couteur 1 on his farm on the isle of Jersey, who cultivated 

 upwards of 150 varieties of wheat, which he claimed were as pure as 

 those of any other agriculturalist. But Professor La Gasca of Madrid, 

 who visited him, drew attention to aberrant ears, and pointed out, 

 that some of them might be better yielders than the majority 

 of plants in the crop, whilst others might be poor types. Thence 

 he concluded that the isolation of the better ones might be a 

 means of increasing his crops. Le Couteur seems to have con- 

 sidered the constancy of such smaller types after isolation as 

 absolutely probable, since he did not even discuss the possibility 

 of their being variable or of their yielding a changeable or mixed 

 progeny. This curious fact proves that he considered the types, dis- 

 covered in his fields by La Gasca to be of the same kind as his other 

 varieties, which until that time he had relied upon as being pure and 

 uniform. Thus we see, that for him, the variability of cereals was 

 what we now call polymorphy. He looked through his fields for useful 

 aberrations, and collected twenty -three new types of wheat. He was, 

 moreover, clear about one point, which, on being rediscovered after 

 half a century, has become the starting-point for the new Swedish 

 principle of selecting agricultural plants. It was the principle of 

 single-ear sowing, instead of mixing the grains of all the selected 

 ears together. By sowing each ear on a separate plot he intended 

 not only to multiply them, but also to compare their value. This 

 comparison ultimately led him to the choice of some few valuable 

 sorts, one of which, the " Belle vue de Talavera,'' still holds its place 

 among the prominent sorts of wheat cultivated in France. This 

 variety seems to be really a uniform type, a quality very useful under 

 favourable conditions of cultivation, but which seems to have de- 

 stroyed its capacity for further improvement by selection. 



The principle of single-ear sowing, with a view to obtain pure and 



1 On the Varieties, Properties, and Classification of Wheat, Jersey, 1837. 



