CHAP. VII. TARLE C. 255 



the same conditions ; but this can hardly be the case, 

 except under the unusual contingency of each individual 

 being surrounded by other kinds of plants in exactly 

 the 'same proportional numbers. For the surround- 

 ing plants absorb different amounts of various sub- 

 stances from the soil, and thus greatly affect the 

 nourishment and even the life of the individuals of 

 any particular species. These will also be shaded and 

 otherwise affected by the nature of the surrounding 

 plants. Moreover, seeds often lie dormant in the 

 ground, and those which germinate during any one 

 year will often have been matured during very different 

 seasons. Seeds are widely dispersed by various means, 

 and some will occasionally be brought from distant 

 stations, where their parents have grown under some- 

 what different conditions, and the plants produced 

 from such seeds will intercross with the old residents, 

 thus mingling their constitutional peculiarities in all 

 sorts of proportions. 



Plants when first subjected to culture, even in their 

 native country, cannot fail to be exposed to greatly 

 changed conditions of life, more especially from 

 growing in cleared ground, and from not having to 

 compete with many or any surrounding plants. They 

 are thus enabled to absorb whatever they require 

 which the soil may contain. Fresh seeds are often 

 brought from distant gardens, where the parent- 

 plants have been subjected to different conditions. 

 Cultivated plants like those in a state of nature 

 frequently intercross, and will thus mingle their 

 constitutional peculiarities. On the other hand, as 

 long as the individuals of any species are culti- 

 vated in the same garden, they will apparently be 

 subjected to more uniform conditions than plants in a 

 state of nature, as the individuals have not to compete 



