This Philadelphian, though a famous plant collector and herbarium owner, must not be confused with the English botanist of the same name and time. These letters are entirely botanical in nature, coming from 55 individuals, and present a cross section of the botanists and their problems in the early 19th century. At Collins' death his fine herbarium was claimed by Rafinesque to settle a debt, but only a portion of it went to that naturalist. Some of the specimens eventually came to this Academy.

Contains a series of letters to Rev. Henry Muhlenberg, 1812-15, to F. A. Muhlenberg, 1815-16, and correspondence with Stephen Elliott, 1813-21. An index, a partial typed analysis of the correspondence, and a microfilm of the entire collection are included.