The letters to Persifor Frazer cover primarily matters related to geology and mineralogy. A portion of the correspondence, principally from British scientists, concerns the 1884 meeting in Philadelphia of the American Association for the Advancement of Science (B F867).

Mostly concerned with Blakeslee's studies on beans, blood groups, colchicine, Datura, embryo cultures, and horticulture. Many letters relate to the support and direction of the Smith College Genetics Experiment Station, which he headed. Other letters are about the Carnegie Institution of Washington, "Biological Abstracts," American Association for the Advancement of Science, American Philosophical Society, Institut de France, University of Connecticut. Also contains travel letters from Germany and miscellaneous lectures.

Britton Chance (1913-2010) was a biochemist and biophysicist as well as a pioneer in the field of biomedical optics. Chance received his Ph.D. in Physical Chemistry from the University of Pennsylvania in 1940 and his Ph.D. in Biology and Physiology from Cambridge University in 1942. Over the course of his nearly eight decade career, Chance was dedicated to the application and transfer of basic scientific research and technology to clinical medicine. The Britton Chance Papers contain correspondence, research notes, experimental data, publication materials, and photographs stemming from Chance's life as a biochemist, biophysicist, and yachtsman. The collection is broken up into fifteen series that document every aspect of his scientific work.

A botanist and historian of science at the University of Pennsylvania, Conway Zirkle published on the history of evolutionary thought and genetics, with a particular interest in the discipline as practiced in the Soviet Union. The Zirkle Papers consist of approximately one linear foot of materials accrued by Zirkle during research for his book on Lysenko-era biology in the Soviet Union, The Death of Science in Russia (1949). Among the miscellaneous materials in the collection are four volumes (0.5 linear feet) of pressed specimens of ferns and algae.