444 GENERAL RESULTS. CiiAr. XII. 



any corresponding degree on the pollen of the self- 

 fertilised parents acting inefficiently on the stigmas of 

 the same flowers ; for in the case of the Ipomoea, 

 Mimulus, Digitalis, Brassica, &c, the self-fertilised 

 parents yielded an abundant supply of seeds ; never- 

 theless the plants raised from these seeds were 

 markedly inferior in many ways to their cross-ferti- 

 lised brethren. Again with Reseda and Eschscholtzia 

 the more self-sterile individuals profited in a less 

 degree by cross-fertilisation than did the more self- 

 fertile individuals. With animals no manifest evil 

 has been observed to follow in the first few generations 

 from close interbreeding ; but then we must remember 

 that the closest possible interbreeding with animals, 

 that is, between brothers and sisters, cannot be con- 

 sidered as nearly so close a union as that between the 

 pollen and ovules of the same flower. Whether with 

 plants the evil from self-fertilisation goes on increas- 

 ing during successive generations is not as yet known ; 

 but we may infer from my experiments that the increase, 

 if any, is far from rapid. After plants have been pro- 

 pagated by self-fertilisation for several generations, a 

 single cross with a fresh stock restores their pristine 

 vigour ; and we have a strictly analogous result with 

 our domestic animals. * The good effects of cross-fer- 

 tilisation are transmitted by plants to the next gene- 

 ration ; and judging from the varieties of the comm<! a 

 pea, to many succeeding generations. But this m*y 

 merely be that crossed plants of the first generation 

 are extremely vigorous, and transmit their vigour, like 

 any other character, to their successors. 



The means for favouring cross-fertilisation and pre- 

 venting self-fertilisation, or conversely for favouring 



* t 



Variation under Domestication,' ch. xix. 2nd edit. vol. ii. p. 159. 



