U.S. Army surgeon who collected plants in the southern United States and Panama. Hayes, a native of New York, studied medicine and after qualifying was appointed assistant surgeon on an expedition surveying a route for emigrants to the Pacific States. The government-sponsored El Paso to Fort Yuma Wagon Road Expedition took two years, during which time Hayes made good use of botanical knowledge he had acquired during earlier studies in Paris. The surgeon's health began to deteriorate during the trip, however. Suffering from tuberculosis, he decided to remove to Panama to recuperate. On his arrival in Colón (then known as Aspinwall) his condition appeared so serious he would not survive long, but the warm climate in fact gave him more than three extra years of life during which he enjoyed collecting tropical specimens until the very last. Botanising around Panama City and the Panama Railway, he sent the fruits of his labours to the Royal Botanic Gardens, Kew and many other herbaria. He discovered many new species and several are named after him.

Sources:
Anon., 1863, Journal of Botany, 1: 254
L.J. Dorr, 2000, "Review: Heckadon-Moreno, Stanley. Naturalistas del Istmo de Panamá" 1998, Taxon, 49(2): 339
W.B. Hemsley, 1888, in F.D. Godman and O. Salvin (editors), Biologia Centrali-Americana, 4: 135.