German physician and botanist in the Caucasus and nephew of J.G. Gmelin, a botanical explorer in Siberia. Samuel Gottlieb Gmelin studied medicine in his home town of Tübingen before visiting Holland where he befriended the explorer and naturalist P.S. Pallas. Gmelin was later named professor of botany at the Academy of Sciences in St. Petersburg and moved to Russia in 1766.

Empress Catherine II was at the time launching many exploratory missions throughout the empire, and Gmelin was sent on an expedition to the Caspian Sea with Pallas and J.A. Güldenstädt in 1768. From St. Petersburg he travelled down to Astrakhan and collected in the North Caucasus. Leaving there by ship in 1770 he visited many Iranian locations on the banks of the Caspian before eventually reaching Mazandaran, where he fell foul of the governor. Luckily Gmelin was given permission to leave and returned to Astrakhan before journeying north a little to the Kuban Steppe. Later he crossed the Caspian again, this time visiting the east coast (present day Kazakhstan) and making interesting ethnographic observations.

Travelling overland around the southern edge of the sea, he was taken prisoner by one of the local Usmi lords near Tehran in 1774. Eventually he was released after lengthy discussions but he had sustained a considerable blow to his health from the poor conditions in which he had been held captive, and died soon afterwards.

Gmelin published two books, a Historia Fucorum in 1786 and Reisen durch Russland zur Untersuchung der drei Naturreiche (Travels through Russia to Investigate the Three Natural Realms) between 1770-1774.

Sources:
W. Floor, commentary on Travels through northern Persia, Mage Publishers:
http://www.mage.com/history/ttnp.html, accessed 9 December 2010
O. Raubenheimer, 1930, "Gmelin, a German family of pharmacists, chemists and botanists", Journal of the American Pharmaceutical Association, 19(3): 259-265.