What scientist first identified that there were different sexes in plants ?

Rudolph Jacob Camerarius

(source) Born 17 Feb 1665; died 11 Sep 1721.
German botanist who demonstrated the existence of sexes in plants, which made plants available for studies of genetics and heredity. He demonstrated experimentally the sexuality of plants in Epistolae de Sexu Plantarum (Letter on the Sexuality of Plants, 1694) in which he identified the stamen and pistil as the male and female organs, and the pollen as the fertilizing agent.