IMPROVING THE HUMAN PLANT 



developer is looking for the production or the 

 accentuation of some quality that may be said to 

 constitute an abnormality; whereas the human 

 eugenist is concerned above everything else with 

 the accentuation of normal qualities and the elim- 

 ination of the elements of abnormality. Neverthe- 

 less the experiments of the plant developer may 

 afford a demonstration of principles of heredity 

 that are susceptible of useful application. 



It is fairly demonstrated, for example, that 

 there is no necessary deterioration brought about 

 by the crossing of plants that are related in the 

 degree which in the case of human beings we de- 

 scribe as cousinship. If the strain is normal and 

 healthy, and in particular if the cousins have 

 grown up under different environment, there is no 

 inherent objection to their mating. That is to say, 

 there is no hereditary reason why they may not 

 produce normal and healthy offspring. The great 

 difficulty, however, is that very few families are 

 quite free from one taint or another of disease or 

 infirmity, and the mating of cousins brings to- 

 gether the hereditary factors for this defect in 

 such combination as to accentuate them, and en- 

 hance the probability that the defect will make 

 itself manifest in the offspring. 



Take, for example, the case of the wild heu- 

 chera with the crinkled leaf from which it proved 



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