PPdMITIVE AGRICULTURE. 3 



the poorer species of their own country. History shows 

 us that wheat, maize, the sweet potato, several species of 

 the genus Panicum, tobacco, and other plants, especially 

 annuals, were widely diffused before the historical period. 

 These useful species opposed and arrested the timid 

 attempts made here and there on less productive or 

 less agreeable plants. And we see in our own day, in 

 various countries, barley replaced by wheat, maize pre- 

 ferred to buckwheat and many kinds of millet, while some 

 vegetables and other cultivated plants fall into disrepute 

 because other species, sometimes brought from a distance, 

 are more profitable. The difference in value, however 

 great, which is found among plants already improved by 

 culture, is less than that which exists between cultivated 

 plants and others completely wild. Selection, that great 

 factor which Darwin has had the merit of introducing 

 so happily into science, plays an important part when 

 once agriculture is established ; but in every epoch, and 

 especially in its earliest stage, the choice of species is 

 more important than the selection of varieties. 



The various causes which favour or obstruct the 

 beginnings of agriculture, explain why certain regions 

 have been for thousands of years peopled by husbandmen, 

 while others are still inhabited by nomadic tribes. It is 

 clear that, owing to their well-known qualities and to the 

 favourable conditions of climate, it was at an early period 

 found easy to cultivate rice and several leguminous plants 

 in Southern Asia, barley and wheat in Mesopotamia and 

 in Egypt, several species of Panicum in Africa, maize, 

 the potato, the sweet potato, and manioc in America. 

 Centres were thus formed whence the most useful species 

 were diffused. In the north of Asia, of Europe, and of 

 America, the climate is unfavourable, and the indigenous 

 plants are unproductive ; but as hunting and fishing 

 offered their resources, amculture must have been intro- 

 duced there late, and it was possible to dispense with the 

 good species of the south without great suffering. It 

 was different in Australia, Patagonia, and even in the 

 south of Africa. The plants of the temperate region in 

 our hemisphere could not reach these countries by 



