I Clarence A. Cheever MD (1858-1947) a successful Milton, Massachusetts physician and amateur botanist built up in his life time one of the most complete diatom collections in the Western Hemisphere. Dr. Cheever first developed his interest in diatoms as an undergraduate student of Dr. W.G. Farlow, at the Bussey Institute of Harvard University. Though he later chose to go on to medical shchool and became a practicing physician, Dr. Cheever never lost interest in botany. In fact for many years he was the editor of The New England Farmer. Interestingly enough the study of diatoms always remained a hobby to Dr. Cheever, despite the fact that he was continually adding to his collection and keeping abreast of the scientific literature on the subject. Although he had obviously become well qualified he never published a single work on the subject of diatoms. The bulk of Cheever's Diatom Herbarium consists of over 10,000 pre- pared slides, representing a world wide gathering of thousands of species and over two hundred freshwater and marine diatom genera. Acquired mainly through purchases, there are dozens of collectors and authors, both pro- minent and obscure, represented in Dr. Cheever's collection. Among these are: F. Habirshaw, H. van Heurch, Wm. H. Pratt, H.H. Chase, D.B. Ward, H.L. Smith, Wm. A. Terry, J.D. Moller, P.F. Cleve, G.A. Fisher, C. Febiger, Wm. A. Poyser, Tempere DeBrebisson, T. Eulerstein, F.F. Forbes, P. Klavsen, C.L. Peticolas, C.H. Kain, O. Kendall Jr., R.P. Durkee, E. Thum, G. W. Morehouse, J.P. Wintringham, T. Chalkley Palmer, J.R. Bartholomew, J.L. Cloud, H. Reichett and W.C. Walker, M.A. Booth, H.S. Lauder, L. Leger, A. Newman, A.C. Wheeler, R.S. Warren, F.W. Lewis, C. Stodder, M.A. Grunow, E. Samuels, J.W. Bailey, J.D. King, N.A. Mason, L. Woolman, F.S. Morton, E. Weissflog, C. Bourgonne, W.H. Harvey, J. Pain. In addition to the slides the Herbarium also includes 500 vials each of W. A. Terry's and F. Habirshaw's cleaned and dried diatoms; a copy of Schmit's Atlas der Diatomacee through plate 336; an extensive card index to species, collection localities and diatom literature and several of Dr. Cheever's note books. The Cheever Diatom Herbarium was received in part as gifts in 1941 and 1943 from Dr. Cheever himself. The remainder of the collection was later donated by his son Austin Cheever in 1953. The restoration organization and indexing of the Cheever Diatom slide Herbarium was begun in June 1974 and completed February 1975. The restoration and organization of the collection was carried out by Shirley Mah, Dan Plas, Ann Faulkner and Jerry Cacavio. The index was prepared by Ann Faulkner and Jerry Cacavio and typed by Alice Panossian.