Robert Brown, (born December 21, 1773, Montrose, Angus, Scotland—died June 10, 1858, London, England), Scottish botanist best known for his descriptions of cell nuclei and of the continuous motion of minute particles in solution, which came to be called Brownian motion. In addition, he recognized the fundamental distinction between gymnosperms (conifers and their allies) and angiosperms (flowering plants), and he improved plant taxonomy by establishing and defining new families and genera. He contributed substantially to the knowledge of plant morphology, embryology, and biogeography, in particular by his original work on the flora of Australia.