Salvia apiana and Salvia mellifera are two common species of sage in coastal California. Over much of their overlapping ranges they give little or no indication that they can (and frequently do) hybridize and that their hybrids are quite fertile. These significant facts were called to scientific attention by Epling. After monographing these and other Salvias taxonomically (Epling, 1938), he studied them experimentally in the field and in the breeding plot. He demonstrated (Epling, 1947) that they hybridize readily when artificially cross-pollinated and that the resulting hybrids are fertile enough to yield variable F-2's and back-crosses. Though these two species grow closely intermingled over thousands of square miles he found little evidence that hybridization did take place except under disturbed conditions. This he interpreted as due to a complex of internal and external barriers. One of the most important is the different adaptive mechanisms for insect pollination in the two species, S. apiana being pollinated largely by bumble bees and S. mellifera by small solitary bees. The problem seemed such an interesting one that the senior author has studied it repeatedly and intensively in the field for somewhat over a decade and has used these two species as field and laboratory material for a summer school course. Population samples from critical areas were pickled for laboratory study, and with the help of the junior author an exhaustive analysis of variation in pubescence, calyx shape, corolla shape, and inflorescence branching was undertaken. This confirms and extends Epling's experimental and field studies. It analyzes a little more precisely the conditions under which the barriers break down between the two species. Thanks are due to Carl Epling, to Harlan Lewis, and to E. G. Anderson for assistance in making the collections. In addition to the various facts collected by Epling, careful study of two quite different matters seemed necessary before we could interpret the hybridization dynamics of these two species: (1) a more complete morphological analysis of the two species and their intermediates; (2) a precise investigation of the disturbed habitats in which intermediates were common.