This collection includes roughly 900 letters, postcards and related items from botanists and their correspondents who were active in the 20th century. The materials themselves range in creation date from the late 19th through the 20th centuries. The collection includes both handwritten and typed letters, almost all of which are signed by their authors. There are few items in the collection that are not accompanying letters (roughly 20), including manuscripts, checks, receipts and other miscellaneous documents.