hybrid with the pure gemmules of the same parts derived from 

 the other would necessarily lead to complete reversion of char- 

 acter, and it is perhaps not too bold a supposition that un- 

 modified and undeteriorated gemmules of the same nature 

 would be especially apt to combine. 



"Pure gemmules in combination with hybridized gem- 

 mules would lead to partial reversion, and lastly, hybridized 

 gemmules derived from both parent-hybrids would simply re- 

 produce the original hybrid form. All these cases and de- 

 grees of reversion incessantly occur" {Variation of Plants 

 and Animals under Domestication). 



This statement comes very close to the modern theory 

 of heterozygosis. 



To Darwin we owe the phrase: "Nature abhors per- 

 petual self-fertilization," which, of course, does not hold 

 true in the case of many vigorous plants, such as tobacco, 

 wheat, and barley. East and Jones state that Darwin's 

 phrase should be changed to read: "Nature discovered a 

 great advantage in an occasional cross-fertilization." It is 

 well known that many plants have special adaptations in 

 their flowers, whereby self-fertilization is prevented; that 

 highly colored flowers are usually cross-fertilized by insects; 

 that the more inconspicuous flowers are cross-pollinatd by 

 wind, etc., etc. Darwin proved by numerous experiments 

 that the products of crosses were usually more vigorous than 

 the parents of the hybrid {Cross and Self Fertilization in the 

 Vegetable Kingdom). 



In one case he grew five pots of cross-fertilized seeds 

 of pansy and an equal number of self-fertilized seeds with 

 the following results: 



Average height of the 14 cross fertilized plants =5.58 



inches. 

 Average height of the 14 self- fertilized plants = 2.37 



inches. 

 Next year the crossed plants produced 167 capsules; 



the selfed plants produced 17 capsules. 

 (Plants turned out of pots and planted in soil) . 



In the following year the area covered by the cross- 

 fertilized plants was about nine times as large as that cover- 

 ed by the self-fertilized plants. During the ensuing winter, 

 which was severe, all the cross-fertilized plants survived 

 and grew vigorously. 



'77 



