These letters from taxonomist Alain White (1880–1951) refer to Letty’s illustrations in the journal Flowering Plants of South Africa, the use of her drawings of Stapelia Linnaeus from that journal in White and Boyd L. Sloane’s The Stapelieae (Pasadena, Abbey San Encino Press, 1937, 3 vols.), and the preparation and publication of the book, in which she is listed as a collaborator. White's letters also cover the use of Letty's drawings in White, Sloane, and R. Allen Dyer’s The Succulent Euphorbieae (Pasadena, Abbey Garden Press, 1941, 2 vols.). References are made by White to Sloane, Inez Verdoorn of Summerville, South Carolina, and M. E. Connell of Litchfield, Connecticut. White’s letter of 10 July 1935 contains some autobiographical data as well.

Also included is one letter (22 June 1937) from Sloane to Letty, written after the publication of The Stapelieae.