450 GENERAL RESULTS. CHAP. XII. 



from the self- fertilisation of plants, is the result of the 

 increase of some morbid tendency or weakness of consti- 

 tution common to the closely related parents, or to 

 the two sexes of hermaphrodite plants. Undoubtedly 

 injury has often thus resulted ; but it is a vain 

 attempt to extend this view to the numerous cases 

 given in my Tables. It should be remembered that the 

 same mother-plant was both self-fertilised and crossed, 

 so that if she had been unhealthy she would have 

 transmitted half her morbid tendencies to her crossed 

 offspring. But plants appearing perfectly healthy, 

 some of them growing wild, or the immediate offspring 

 of wild plants, or vigorous common garden-plants, were 

 selected for experiment. Considering the number of 

 species which were tried, it is nothing less than absurd 

 to suppose that in all these cases the mother-plants, 

 though not appearing in any way diseased, were weak 

 or unhealthy in so peculiar a manner that their self- 

 fertilised seedlings, many hundreds in number, were 

 rendered inferior in height, weight, constitutional 

 vigour, and fertility to their crossed offspring. More- 

 over, this belief cannot be extended to the strongly 

 narked advantages which invariably follow, as far as 

 my experience serves, from intercrossing the indivi- 

 duals of the same variety or of distinct varieties, if 

 these have been subjected during some generations to 

 different conditions. 



It is obvious that the exposure of two sets of plants 

 during several generations to different conditions can 

 lead to no beneficial results, as far as crossing is con- 

 cerned, unless their sexual elements are thus affected. 

 That every organism is acted on to a certain extent by 

 a change in its environment, will not, I presume, be 

 disputed. It is hardly necessary to advance evidence 

 OD this head ; we can perceive the difference between 



