At such times the seeds of all sorts of little annual plants, including grasses, daisies, lupines, and a host of others, sprout quickly, and give rise to a carpet of vegetation as varied and beautiful as that of the prairie. Thus the desert has not only its own peculiar bushes and succulents but many of the products of vegetation in swamps, grasslands, and forests. Though much of the ground is bare in the desert, the plants are actually crowded together as closely as possible. The showers of such regions are usually so brief that they merely wet the surface. At a depth of a foot or more the soil of many deserts never becomes moist from year's end to year's end. It is useless for plants to send their roots deep down under such circumstances, for they might not reach water for a hundred feet. Their only recourse is to spread horizontally. The farther they spread, the more water they can absorb after the scanty showers. Hence the plants of the desert throttle one another by extending their roots horizontally, just as those of the forest kill one another by springing rapidly upward and shutting out the light. Vegetation, whether in forests, grasslands, or deserts, is the primary source of human sustenance. Without it man would perish miserably; and where it is deficient, he cannot rise to great heights in the scale of civilization. Yet strangely enough the scantiness of the vegetation of the deserts was a great help in the ascent of man. Only in dry regions could primitive man compete with nature in fostering the right kind of vegetation. In such regions arose the nations which first practised agriculture. There man became comparatively civilized while his contemporaries were still nomadic hunters in the grasslands and the forests. CHAPTER V. THE RED MAN IN AMERICA When the white man first explored America, the parts of the continent that had made most progress were by no means those that are most advanced today. * None of the inhabitants, to be sure, had risen above barbarism. Yet certain nations or tribes had advanced much higher than others. There was a great contrast, for example, between the well-organized barbarians of Peru and the almost completely unorganized Athapascan savages near Hudson Bay. * In the present chapter most of the facts as to the Indians north of Mexico are taken from the admirable "Handbook of American Indians North of Mexico," edited by F. W. Hodge, Smithsonian Institution, Bureau of Ethnology, Bulletin 30, Washington, 1907, two volumes. In summing up the character and achievements of the Indians I have drawn also on other sources, but have everywhere taken pains to make no statements which are not abundantly supported by this authoritative publication. In some cases I have not hesitated to paraphrase considerable portions of its articles.