ning of agriculture. Success was not difficult in regions where propitious conditions of soil and climate favored the propagation of plants of great productiveness. Observation and experiment next fixed the elements of a theory, limited at first to a few species, then extended and perfected by degrees. To reach these feeble beginnings by the rational methods of agriculture, a long series of attempts marked by more failures than successes had to be gone through. Gradually, however, the processes were improved; the resources increased, and the profits of vegetable production, so long surpassed by those of the hunt and of cattle-raising, at last prevailed over them; and this determined the adoption of a special kind of life, the consequences of which were destined to transform the condition of man.
Regarded as a whole, the cultivation of plants was a more complex and more arduous problem than the domestication of animals. To subject animals, it was enough to capture and hold them. They were then tamed as they became familiar, and afterward required nothing more than watching or protection. They could themselves provide for their wants, or make them known in a language easy to understand. They spontaneously sought their food and fled from danger. The mothers suckled and defended their little ones. Animal instinct thus saved the master of the herd much trouble. Plants, on the other hand, although their passive nature is apparently less rebellious to subjection than the undocile character and self-will of animals, really opposed more obstacles by the very fact of their lack of activity, on account of which they could not help and be sufficient for themselves. Constant watchfulness had to be exercised to see that their growth was accomplished regularly, for their needs never became evident till they were dying, and intelligent cares are necessary to prevent this or remedy it. Taking the propagation of plants under his charge, man had to choose a favorable soil for them, to break it up by toilsome labor, to put the seed in at the proper time, to stimulate their growth with manures, to furnish them water, warmth, and light, according to their needs. Their reproduction, in the wild state, was accomplished in the midst of innumerable risks, under the laws of the struggle for existence, and multiplicity of seeds could alone, in the face of a fearful loss, make sure the duration of species. In the hard and incessant struggle to which plants were given in the contest for ground and a place in the sun, the most precious, which were also usually weak and delicate, were liable to be smothered. To cause them to increase, man had to interfere in the conflict, to extirpate useless, vigorous, and aggressive species, and procure for those under his protection conditions of development. It was necessary, therefore, to clear, plow, and weed; to study the phenomena of vege-
