Title: Correspondence
Subjects: Correspondence, Opuntia, Botanical specimens, Cereus, Barter, Echinocactus, Collectors and collecting
Places: Mogollon Mountains, New Mexico
People: Henry Hurd Rusby (1855-1940), F. A. Wislizenus (1810-1889), George Engelmann (1809-1884), Asa Gray (1810-1888)