Title: Correspondence
Subjects: Correspondence, Ephedra, Botanical specimens, Eriophyidae, Fagaceae, Gnetaceae, Erineum, Euphorbiaceae, Euphorbia
People: George Engelmann (1809-1884), Friedrich August Wilhelm Thomas (1840-1918), Wilhelm Olbers Focke (1834-1922), Alexander Braun (1805-1877)