CHAPTER IX 



SWOLLEN ROOTS AND TUBEROUS STRUCTURES 



THE roots of many herbaceous plants grow 

 vertically downwards ; and under cultivation, in 

 which much nourishment is artificially supplied, 

 the roots increase in size, until the garden forms 

 are acquired, such as those of the carrot, parsnip, 

 turnip, radish, etc., all of which are wild flowers 

 of England, with wiry inedible roots. 



Darwin compared natural selection to artificial 

 selection, and these roots ought to furnish a 

 good illustration. 1 A profound difference, how- 

 ever, should have been noticed, but is always 

 ignored ; and that is, while the majority in the 

 wild state are supposed to perish from some 

 inherent injurious variations of structure ; yet if 

 seed happen to reach a new environment, when 

 the gardener selects the best roots and rejects 

 the majority, the latter would have lived just 

 as well as the ones selected. A garden is only 

 an improved environment-, how is it that no 

 seedling ever produces a mortal variation ? 2 It 



1 " Origin of Plant Structures," ch. ix., p. 179. 



2 Called by Darwin " injurious," by which he meant an " in- 

 adaptive " variation of structure, the actual cause of death, 



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