Martín Sessé y Lacasta (December 11, 1751 – October 4, 1808) was a Spanish botanist, who relocated to New Spain (now Mexico) during the 18th century to study and classify the flora of the territory. Background Sessé studied medicine in Zaragoza, then moved to Madrid in 1775. In 1779 he became a military physician, in which capacity he visited Cuba, and later New Spain. In 1785 he was named a commissioner of the Royal Botanical Garden in New Spain. At the same time a botanical garden and a course of study on the flora of Mexico at the Royal and Pontifical University of Mexico (now UNAM) were authorized. Sessé stopped practicing medicine in order to devote all his energies to botany. The botanical expedition In 1786 Charles III, King of Spain, authorized a major botanical expedition known as the Royal Botanical Expedition to New Spain, that was proposed by Sessé at a time when most of the flora and fauna of Mexico were unknown to European science. Sessé became the head of the expedition and of the botanical garden. His preparation for the expedition began in 1787. It was extensive, and took some time. He visited Santo Domingo, Puerto Rico, and Cuba, where similar (though smaller) studies had already been undertaken, to collaborate and learn. In Cuba he collaborated in the search for a treatment of a parasitic illness that had been spreading rapidly. Back in New Spain, he was joined by a group of Spanish botanists selected by Casimiro Gómez Ortega, director of the Royal Botanical Garden of Madrid. These included Vicente Cervantes, the first professor of botany in New Spain, who continued to live in the country until his death in 1829; José Longinos Martínez, who organized the Gabinete de Historia Natural, the precursor of the Museum of Natural History; Juan Diego del Castillo, pharmacist and botanist; and José Maldonado. Also among the botanists was José Mariano Mociño, a native of New Spain. Juan Cerda was the official artist of the expedition, and the Mexican Atanasio Echeverría was also one of the artists. The genus Echeveria was named for him. Various companies of scientists were sent to such widely separated destinations as the Pacific coast of Canada, the Greater Antilles, Yucatán, Nicaragua, and San Francisco. Sessé and Mociño worked mostly in the central part of Mexico. The tasks of the expedition included collecting specimens and having paintings of