34 PLANT-BREEDING 



have approached this high degree of invariability in the pro- 

 ducts of Le Couteur's selection, and only at present is it 

 recognized as an instance of one of the most common laws, 

 which rule the phenomena involved. 



Another celebrated breeder who worked on the same 

 principle, though after a somewhat different method, was 

 the Scottish agriculturist, Patrick ShirrefT. He lived in 

 about the middle of the nineteenth century and had his 

 farm at Haddington in Haddingtonshire. During the first 

 period of his work, he had no better conception concerning 

 the purity of his fields than his contemporaries. But he 

 observed that, from time to time, and as he thought by mere 

 accident, a plant occurred which seemed far more promis- 

 ing than all the remainder of the same field. Such individ- 

 uals he marked, helping their development by pulling out 

 their neighbors if they were crowded and surrounded them 

 by all manner of attention. Then he saved their seeds 

 separately and sowed them, in order to multiply his new 

 types as fast as possible. That such isolated individuals 

 would yield a uniform progeny and become the ancestors of 

 constant races he took for granted, and it is very curious to 

 note in his writings that he did not judge it worth while to 

 discuss this point, or to state the fact as he observed it. 

 His races were pure, and there was no single reason for him 

 to suggest that it could have been otherwise. 



ShirrefPs exceptional plants were very rare, so rare even 

 that in the first period of nearly forty years, he succeeded 

 in isolating only four new varieties of prominent value. 

 His first discovery was made in the year 1819. He observed 

 a plant of wheat which surpassed its neighbors by its high 

 degree of branching. It yielded 63 ears with about 2500 

 kernels. He saved the seeds, sowed them on a separate 

 field and at considerable distances apart so as 'to induce in 

 all the plants the same rich branching. He contrived to 



