French naturalist and surgeon with the merchant navy. Vieillard explored New Caledonia and Tahiti in 1855-1867, making extensive botanical collections. As a 'médecin de la marine' he was posted first to Tahiti (1855-1857), where he collected with gardener-botanist Isadore Pancher, and then to four garrisons on New Caledonia with his colleague and co-collector Emile Deplanche. He took a year's leave in 1861, devoting several months to collecting ferns in New Zealand, as well as exploring the Cape of Good Hope and Réunion en route back from France. In New Caledonia he collected algae and land plants, amassing more than 12,000 specimens, which were sent to France for distribution to botanists in Europe. He numbered them according to species rather than specimens, however, meaning that different specimens of the same species, although collected on different dates and in different localities, share a number. Vieillard published several works on the plants of New Caledonia in the 1860s and became a respected botanist, and after his return to France was appointed Professor of Botany and director of the Botanical Garden at Caen in northern France. He remained at Caen from 1871-1895. More than 35 species of plant have been named in his honour.

Sources:
O. Lignier, 1905, "Essai sur l'histoire du Jardin des Plantes de Caen", Bulletin de la Société Linnéenne de Normandie, sér. 5, 8: 130
M.E. McKee and H.S. McKee, 1981, "E. Vieillard et E. Deplanche, deux grands botanistes collecteurs en Nouvelle-Calédonie", Histoire & Nature, 17-18: 49-68.