Robert Brown (1773-1858)
A Scotsman who discovered the brownian movement of minute particles (1828), a phenomenon that provides a basis for demonstrating molecular motion. He later discovered the general occurrence of the nucleus in plant cells (1831). He first observed (1827) that pine trees and their kin have ovules (undeveloped seeds) and mature seeds that are naked (not protected by an ovary). He classified gymnosperms and separated them from true, flower-bearing angiosperms (1825). He discovered the minute areola (spaces) in pollen grains, which he regarded as points for the production of pollen tubes.