CLOSE AND CKOSS FEKT1L1ZAT1ON CONTRASTED. 449 



IPOM<EA PURPUEEA. 



1153. The results of close and cross fertilization, as shown by 

 the weight of the seed-capsules, are given by Darwin thus : " The 

 offspring of intercrossed plants of the ninth generation, crossed 

 by a fresh stock, compared with plants of the same stock inter- 

 crossed during ten generations, both sets of plants left uncovered 

 and naturally fertilized, produced capsules by weight as 100 

 to 51." l 



1 The following summary (Darwin : Effects of Cross and Self Fertilization, 

 p. 56) shows more of the results : 



First generation of crossed and self-fertilized plants growing in competition 

 with one another. Sixty-five capsules produced from flowers on five crossed 

 plants fertilized by pollen from a distinct plant, and fifty-five capsules pro- 

 duced from flowers on five self-fertilized plants, fertilized by their own pollen, 

 contained seeds in the proportion of 100 to 93. 



Fifty-six spontaneously self-fertilized capsliles on the above five crossed 

 plants, and twenty-five spontaneously self-fertilized capsules on the above five 

 self-fertilized plants, yielded seeds in the proportion of ... 100 to 99. 



Combining the total number of capsules produced by these plants and the 

 average number of seeds in each, the above crossed and self-fertilized plants 

 yielded seeds in the proportion of 100 to 64. 



Other plants of this generation grown under unfavorable conditions and 

 spontaneously self-fertilized yielded seeds in the proportion of . 100 to 45. 

 2P 



