GEOGRAPHY OF PLANTS. 67 



ploying the varying resources of the elements, 

 with an inexhaustible fertility of contrivance, a 

 constant tendency to diffuse life and well being. 



2. One of the great uses to which the vegetable 

 wealth of the earth is applied, is the support of 

 man, whom it provides with food and clothing ; 

 and the adaptation of tribes of indigenous vege- 

 tables to every climate has, we cannot but believe, 

 a reference to the intention that the human race 

 should be diffused over the whole globe. But this 

 end is not answered by indigenous vegetables 

 alone ; and in the variety of vegetables capable 

 of being cultivated with advantage in various 

 countries, we conceive that we find evidence of 

 an additional adaptation of the scheme of organic 

 life to the system of the elements. 



The cultivated vegetables, which form the 

 necessaries or luxuries of human life, are each 

 confined within limits, narrow, when compared 

 with the whole surface of the earth ; yet almost 

 every part of the earth's surface is capable of 

 being abundantly covered with one kind or other 

 of these. When one class fails, another appears 

 in its place. Thus corn, wine, and oil, have each 

 its boundaries. Wheat extends through the old 

 Continent, from England to Thibet : but it stops 

 soon in going northwards, and is not found to 

 succeed in the west of Scotland. Nor does it 

 thrive better in the torrid zone than in the polar 

 regions : within the tropics, wheat, barley and 



