istic of such an area is the tendency to specialize in some one or two foods. Reference to the initial chapter of this work will make this point clear. For example, we have, centering in California (3), the use of the acorn; in the Plains (1), the bison; in parts of both continents, maize; and in the Amazon country (14), manioc. At all these culture centers we find more or less elaborate processes of preparation involving technical knowledge, for example, the making of acorn flour and bread, the roasting of camas, etc. These processes tend to spread throughout the area of supply. Thus, the acorn industry extends well up into Oregon far beyond the California center; the roasting of camas (2) to the mouth of the Columbia, and also to the Blackfoot of the Plains, etc. Again, we note certain specializations of manufacture: California (3), baskets; North Pacific Coast (4), boxes and plank work; the Plains (1), rawhide work (parfleche, bags, etc.); Mackenzie (6), birchbark (canoes, vessels, etc.); Plateau (2), sagebrush weaving; Southwest (9), textiles and pottery; Southeast (8), cane and fiber weaving; the Eastern Woodlands (7), knot bowls and bass fiber weaving, etc. Types of shelter present similar distributions, and so do many other traits. All of these traits are seen to reach out far beyond the borders of the respective culture centers, and such extensions can, in the main, be correlated with faunal and floral distributions. Yet, not even all of the more material traits can be considered dependent upon the fauna and flora, for example, pottery. Also, art and ceremonies are no less distinctive and, as we have seen, are also localized in these same centers. In this case, the influence of the environment could be but remote. In any case, we find that the people in a culture area have chosen but a few of the possibilities and specialized in them, leaving many other resources untouched. It is, of course, plain that, if the directions of this specialization varied, many different kinds of culture could successively occupy the same geographical area.
Apparently, the chief explanation of this phenomenon lies in man himself. A group of people having once worked out processes like the use of acorns, maize, manioc, etc., establish
