On any theory of evolution, differences between individuals are compounded somehow into specific and eventually into generic differences. An efficient analysis of plant-to-plant variation should give us critical data for determining the origin of the basic variability which is the raw material for evolution. If, as is currently generally believed, this basic variability results from gene mutation, then an efficient analysis of individual-to-individual differences should reveal the kind of local differentation pattern which might be explained on such an hypothesis. For such studies Adenostoma fasciculatum, the common chamise of coastal California, is excellent material. Over a large part of its range, plant-to-plant variation is so conspicuous as to compel attention. In the hills behind Palo Alto or on the burned-over slopes of Mt. Diablo, virtually any three or four plants of Adenostoma chosen at random can be used to demonstrate the magnitude of this variation and its strongly germinal basis (figs. 1 and 2). If we examine adjacent bushes of Adenostorna along a mountain pathway, it is easy to show that though they are growing so closely side by side that their branches interlock, we can readily distinguish the branches of any one bush by the general similarity of their inflorescences. Though parts of some bushes may be in the sun and parts in the shade, though some branches may be strong terminal leaders and others physiologically suppressed, all the branches on any bush have a nucleus of common features, while the differences from one plant to another are always perceptible and are frequently conspicuous. If we choose a few good-sized bushes and remove the terminal inflorescences from each four to five well-developed branches from each and lay them in the pathway, an independent observer can easily determine from exactly which bush in the vicinity each set of branches was collected. By actual experiment it has been determined that under these conditions a class of students can match up a series of branches with a series of bushes without a single error. Any three such Adenostomna bushes are as different from each other as are three named varieties of lilacs in a collection in a botanical garden. Like the lilacs, they have a strong tendency for all the trusses of bloom on any one bush to be recognizably similar and yet for the trusses to vary perceptibly (and sometimes conspicuously) from one plant to another. Unlike the lilacs, however, the variation is largely confined to differences in the size and branching pattern of the inflorescence. Frequently this may be the only noticeable difference between adjacent bushes, though occasionally one may also find single plants which differ in height, in length of the leaves, in leaf shape, and (even more rarely) in the scurfiness or pubescence at the base of the calyx. Flower color, flower size, and flower shape are not noticeably different in any of the material.