178 The Origin of Species by Mutation. 



sowings of pure bred kinds for a space of a few years 

 to find out which of them were the most valuable. The 

 offspring of these sorts proved to be pure and constant; 

 and his original field must therefore have contained 

 simply a mixture of these sorts. Le Couteur continued 

 to grow the best of the kinds thus purified with such 

 success that he put them on the market with no small 

 advantage to himself; even now some of them are still 

 very well known, as for example the Bcllevne dc Tala- 

 vera. 



Wheat was therefore at that time a mixture of dif- 

 ferent sorts; Le Couteur seems to have been the very 

 first to isolate these units. ^ And even now the common 

 types of wheat are still mixtures. The mixture main- 

 tains itself without artificial selection, but the pure form 

 does not.^ 



Later, Patrick Shirreff in Scotland worked on the 

 same lines as Le Couteur w^ith various forms of cereals. 

 He used to look in his own fields and in those of his 

 friends for striking and apparently better examples : then 

 he sowed their seeds separately and examined their off- 

 spring. As a rule they turned out to be constant and 

 often very productive. In this way he found the original 

 of Mungo swells wheat in 1819, Hopetozvn oats in 1824, 

 Hopetozvn wheat in 1832, and later Shirreff' s oafs.^ 

 They were absolutely constant and as soon as a sufficient 

 quantity of seed had been obtained by cultivation for two 



^ At that time nobody thought of improvement : the idea did not 

 arise till about 50 years later. 



^ See p. 98. 



' V. RiJMKER, loc. cit., p. 70. See also the account of Dr. Hesse's 

 travels in Landw. Jahrb., VI, 1877, p. 850 et seq., and Shirreff's 

 Improvement of Cereals, London, 1873. 



