His intense interest in the lives of early American botanists, especially those whose names appeared on the Academy's herbarium sheets as collectors, led to his accumulating a great deal of historical material over the years. Much in demand as a lecturer on this subject, he presented biographical sketches which were often published later. Included in this collection are finished biographies as well as his notes. Memoranda about botanical collectors have been roughly sorted into 10 categories, according to name sequence on herbaria sheets, geographical region, country and specialty. One folder is devoted to Quaker botanists.