As a student of the flora of southern California, the author has long felt the need of some one book containing descriptions of the native plants. While it is essential that one doing critical work should laboriously search through scattered literature, the average student, and especially the novice, will find such a course impossible. In an endeavor to supply this need, the author has written this book. Not that he feels that the flora is so well known that such a work will prove adequate for years to come, but rather to bring together what knowledge now exists concerning the systematic side of our most interesting plant life. That many mistakes must unavoidably occur, and that many plants are yet to be added, is clearly apprehended.<br><br>The exact area included in this volume is the coast slope of Los Angeles and Orange Counties. This territory comprises a large portion of the great southern California valley, as well as the following mountain ranges, in each of which is named the culminating point: Sierra Santa Monica (Castro Peak 3946 ft.), Sierra San Fernando (San Fernando Peak 3793 ft.), Sierra San Gabriel (Mt. Gleason 6493 ft., San Gabriel Peak 6172 ft., Mt. San Antonio 10080 ft.), Sierra Santa Ana (Santiago Peak 5675 ft.). A number of the more conspicuous and common plants of southern California not known to occur within our boundaries are included, however, so that the student will find that a great majority of the plants to be met with on the coast slope south of Point Conception are described.