This collection contains three letters (1873–1874) and part of a fourth (n.d.), all from George Engelmann in St. Louis to Girard, concerning the flora of Camp Apache, Arizona, where Lt. Girard was serving as a U.S. Army surgeon. Engelmann asks questions about the flora, gives information and collects advice, and refers to various botanical works. Plants referenced include Agave, Cactaceae, Juniperus, Pinus, Quercus, and Yucca.

Also included is a list (by Girard?) of the local flora and a letter (14 August 1880) from Asa Gray to “Dr.” The letter identifies specimens sent and refers to ones still to be sent to Cambridge “after I go”; the letter begins, “Off in three weeks!”