plants, discovered elsewhere, of which the advantage is evident, and are thereb}^d ivert3d from the cultivation of PRIMITIVE 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 preferred 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 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 fishingoffered their resources, agriculture must have been introduced there late, and it was possible to dispense with the good species of the south without great sufi'ering. It was difi'erent 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 4) ORIGIN OF CULTIVATED PLANTS. reason of the distance, and those of the intertropical zone were exchidcd by pjreat droufrlitor by the absence of a hi^h teinporature. At the same time, tlic indigenous species are very pooi'. It is not merely the^vant of intelligence or of security "which lias prevented the inhabitants from cultivating them. ' De Nai'laillac, Les Premiers Hommes et Ics Temps Prt^istoriqnes, i. pp. 266, 208.The absence of traces of agi-icuUure among these remains is, moreover, corroborated by Ueer and Cartailhac, both well versed in the discoveries of archseology.* Heer, Lie I'Jlanzen der P/ahlbauten, in 4to, Zurich, 18C5. See the article on " Flax."