62 DISCONTINUOUS VARIATION. 



Starting with plants which had one or two peloric 

 flowers, he bred and selected them through several gen- 

 erations, and ultimately obtained some entirely peloric 

 plants. These plants were most of them sterile, but a 

 few yielded seeds, and ultimately De Yries obtained a 

 peloric race, Linaria vulgaris peloria, only 10 per cent, 

 of the seeds of which reverted to hemipeloric plants 

 (i. e. 7 plants with some peloric and some non-peloric 

 flowers). According to De Vries, this new race is a 

 true mutation, because the pure peloric plants from 

 which it was derived arose suddenly, and apparently 

 capriciously, from hemipeloric parents. He also ob- 

 tained new races of other plants by artificial selection 

 extending through several generations, but these he 

 regards only as varieties, and not true species, in that 

 their formation was gradual. However, there seems 

 to be no valid ground for sharply differentiating them 

 in this manner. For instance, in the case of the five- 

 leaved clover race (Trifolium pratense quinque folium) 

 obtained by him,* he started breeding with two natu- 

 rally occurring clover plants which had four leaflets to 

 their leaves, and in the case of one leaf, five leaflets. 

 It is difficult to understand why these naturally occur- 

 ring plants should not be regarded as true mutations, 

 just as much as the peloric race above mentioned, or 

 why, indeed, the naturally occurring hemipeloric plants 

 from which the peloric race was obtained were not like- 

 wise true mutations. 



In the case of the clover, the breeding was continued 

 through several generations, the seed of only the few 

 plants richest in four or more leaflets being preserved 



* LOG. cit., p. 437. 



