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for helpful suggestions and data as to occurrence. He is greatly indebted to Dr. Elbert Ahlstrom for assistance in reading manuscript and proof and checking of bibliographical references. He is under especial obligations to the artist, Mr. Alexander Chudom, whose illustrations require no commendation to be appreciated. These have been prepared by him from living material with the exception of S. calif ornica and S. Brandegei. Drawings of the flowers were made by the author from living plants and copied in wash by the artist. The calyces are shown without pubescence. The outline maps show the approximate limits of each species in so far as known. The author is further indebted to Mr. "William Stewart for pollen smears of several species and hybrids. His obligations should also be recorded to Mr. J. E. Harding for his courtesy at El Arco no less than to Mr. N, R. Vail for his hospitality on Santa Rosa Island.The chief prior treatments are as follows :

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