448 



JSXPEEIMENTS WITH PLANTS 



'_''il. Four-, five- and seven- 

 leaved Clover. 



bore (in addition to the normal leaves) one four -leaf 

 and one five-leaf, he sowed its seed and found that 

 about half the resulting plants bore 

 (in addition to normal leaves) four- 

 and five-leaves. The best four plants 

 were saved and their seed sown: 

 this time 80 per cent of the offspring 

 had the four- and five-leaves 

 and a few six- and seven - 

 leaves made their appear- 

 ance. This process of selec- 

 tion was continued until 

 practically all the offspring 

 were of the new type (i. e., three- to seven- 

 leaved, Fig. 251), or, in other words, the seed 

 came true. One might suppose that it would 

 now be possible to go on and make plants 

 with eight and nine leaves. The attempt, 

 however, proved fruitless. The limit of selec- 

 tion was reached with seven, and it was im- 

 possible to go beyond it. On the ground of 

 UKUiy similar experiences, he comes to the 

 conclusion that all plants have a limit which 

 is quickly reached by selection, and here its 

 power ends.i The improved race is not a species: 

 it has no constancy, and when left to itself quickly 

 returns to the original ty]ie. 



'He liclicves tlinr it is even possililc Id lill licl'ini'liaiiil liow iiir.cli n 

 plant can be improved by selection ami where Uie limit will be. 



