local and ephemeral trials must have passed. Determining influences were needed to incite these trials, to secure their renewal, and bring them to success. We can easily understand what they were.
The first thing necessary was to have within reach some plant offering qualities desirable to all men. The most backward savages are acquainted with the plants of their own country; but the Australians and Patagonians are examples to show that, if they do not judge them productive and easy to raise, they do not think of putting them under cultivation. Other conditions are quite evident: a climate not too rigorous; in hot countries, freedom from too long drought; some degree of security and fixedness; and, last, a pressing necessity resulting from failure of resources in fishing, hunting, or the production of the nutritious fruits of native plants, such as the chestnut, the date, the banana, or the bread-fruit. When men can live without working, that is what they prefer. Besides, the element of chance in hunting and fishing tempts primitive men—and some civilized ones too—more than do the difficult and regular labors of agriculture. To return to the species which savages may be disposed to cultivate. They find them sometimes in their own country, but frequently they receive them from neighboring people who are more favored by natural conditions than they, or have already entered upon some degree of civilization. Unless a people is cantoned in an island or in some place difficult of access, it will speedily receive those plants discovered elsewhere whose advantageous qualities are evident, and this will divert them from the cultivation of the inferior species of their own country. History teaches us that wheat, maize, the yam, several species of the genus Panicum, tobacco, and other plants—particularly annual ones—became widely diffused before the historical period. These good species encountered and arrested the timid efforts which might have been made here and there with less productive or less agreeable plants. In our own days, we see, in different countries, wheat taking the place of rye, maize preferred to buckwheat, and many grains, vegetables, and economical plants falling into neglect because other species, often brought from a distance, offer more advantages. The disproportion in value is, however, less between plants already cultivated and improved than formerly existed between cultivated plants and quite wild ones. Selection—that grand factor which Darwin has had the merit so fortunately to introduce into science—plays an important part when agriculture is once established; but in every period, and especially in the beginning, the quality of the species is more important than the selection of varieties.
The various causes which favor or oppose the beginnings of agriculture will explain why some regions have been for thousands of years populated by cultivators, while others are still inhabited by wandering tribes. Rice and several legumes in Southern Asia, barley and wheat in Mesopotamia and Egypt, several grain-plants in