This collection includes letters between Ingenhousz and European and American scientists.

All but one of these letters are to Charles Alston, the professor of botany at Edinburgh University, and concern medicine, botany, and science in general. They are dated between 1737 and 1750. One letter is to George Whately, dated 1778.

These letters and papers include a memorandum book (1795-1827), lectures on botany and medicine, genealogical materials, committee reports from Columbia College, speeches, minutes of the New York Horticultural Society (1822-1828), letters to Sir James Edward Smith (1817-1826), a receipt book of Alexander Hosack (1781-1801), and diaries of Thomas K. Wharton (1830-1862).

This collection contains material relating to his legal affairs, medical publications, receipts for books purchased, and information on botany. Important correspondents include Edward H. Clarke, George Mifflin Dallas, Samuel David Gross, and Joseph Henry. There is also family history in these papers.