Although Scottish botanist Robert Brown (1773-1858) was responsible for discovering the nucleus of a cell, he is perhaps best known for his discovery of the random movement of microscopic particles in a surrounding solution, later referred to as "Brownian motion." He also developed alternative plant classification systems.

Robert Brown was born in Montrose, Scotland--the son of an Episcopalian minister. Although he later discarded his religious faith, Brown gained an appreciation for high intellectual standards from his father. He studied at Marischal College in Aberdeen, and completed his medical studies at Edinburgh University in 1795.

Met Future Collaborator

Immediately after graduation, Brown served as an assistant surgeon in the Fifeshire Regiment of Fencibles, an army regiment stationed in Northern Ireland. His journal entries during this period suggest that Brown's military duties did not demand much of his time. Not one to waste time, Brown's intellectual curiosity led him to study the German language. He also continued his botanical pursuits, memorizing the structures of various plants such as ferns and mosses. His knowledge of German later helped Brown recognize a significant scientific work in that language (Geheimniss der Natur im Bau und in der Befruchtung der Blumen, by C.K. Sprengel, 1793) and bring it to the attention of peer and fellow scientist, Charles Darwin, in 1841.

During a 1798 military recruiting trip to London, Brown was introduced to Sir Joseph Banks. Banks was a prominent lover of botany who used the resources in his home (which included a large library and plant room) to create a botanical center for enthusiasts in the region. Banks was particularly interested in meeting Brown, who had been highly recommended by a peer, Jose Correa da Serra. Both Banks and his current botanist librarian were impressed with Brown's intellectual tenacity. The meeting between Brown and Banks was fortuitous and would later provide the young Scottish botanist with opportunities that would enhance his career. Brown continued to serve as an army official in London during 1798, but was not forgotten by Banks.

A Notable Expedition

A few years after their original meeting, Banks chose Brown to serve as a naturalist for an expedition by sea (beginning in 1801). The chief purpose of the expedition was to study the flora and fauna of the north and south coasts of Australia. Banks used his influence with the Admiralty (who sponsored the voyage) to secure the position for Brown. In typical fashion, Brown spent much of his time preparing for the expedition by studying what was known about the plants of Australia. Captain Matthew Flinders led the expedition. The team of naturalists made several stops including King George Sound (which proved to host a wealth of previously undiscovered plant species), and Port Jackson. Brown spent ten months in Port Jackson, while the ship returned to Timor for provisions. By the time Brown returned to London in 1805, he had collected over 4,000 samples of plants, supplemental drawings, and specimens for zoological research. Banks convinced the Admiralty to give him a salary for classifying and describing the plant samples that had been collected. The task took Brown an additional five years. Brown's collection included 2,200 species of plants, at least 1,700 new species, and 140 new plant genera.

Publication Proved Disappointing

While Brown catalogued his collection from the expedition, he also served as librarian for the Linnean Society, beginning in 1806. He also served as Banks' librarian, beginning in 1810. During that year, Brown published Prodromus Florae Novae Holandiae et Insulae Van Diemen, a study of Australian flora. The study modified one of the prevailing systems of plant classification (the Jussiaean system) by adding new families and genera and including observations about plants worldwide. Even though the study was well received by peers and botanists, Brown had to pay the costs of publication and was only able to sell 24 of 250 printed copies. This effort appeared to have discouraged him and Brown never completed a companion volume that would have covered other plant families from the expedition. Fortunately, Brown's botanical observations were also recorded in his memoirs, such as his "General Remarks, Geographical and Systematical, on the Botany of Terra Australis"; a piece that was published in Flinders' A Voyage to Terra Australis in 1814. Brown's disappointing experience while publishing his study of Australian flora affected the style of his future work. He attempted no further broad syntheses, but instead published his discoveries or thoughts as appendages to other works or as pieces of his memoirs.

A Parting Gift

Banks, who had already provided the botanist with opportunities and resources for advancement, gave Brown one final gift. When he died in 1820, Banks' entire library and all collections were left to Brown. According to the terms of the Banks will, these library collections were to be transferred to the British Museum after Brown's death. However, Brown did not wait until his own death to share the wealth of information that Banks had left. With typical pragmatism, Brown took it upon himself, in 1827, to convince staff at the British Museum to establish a new botanical department, comprised of the Banks collection. They agreed, and Brown ran the botanical department until his death. The collection was notable for being the first nationally owned collection of such material in Britain that was available to the public as a resource.

An Important Discovery

During microscopic research performed in 1827, Brown made his biggest discovery. While observing the sexual organs of plants under the microscope, the scientist found that pollen grains seemed to be darting around in a random manner. Curious, Brown studied other substances under the microscope in search of the same movement. He discovered that if particles were of a certain size (or smaller), that the movement continued to occur. Brown observed the same movement in glass and rock particles, and theorized that the movement was not limited to living matter. The botanist concluded that the movement was caused by some phenomenon of physics and named the phenomenon "Brownian motion." In 1905, Albert Einstein suggested that Brownian motion was the result of the particles colliding with molecules. Nobel Prize winner, Jean Perrin, proved that Einstein's thesis of Brownian motion was correct. Brown's discovery provided the first evidence that proved the existence of atoms. The phenomenon of Brownian motion also led scientists to quantify Avagadro's number--a physical constant for describing random motion.

Brown continued his work in botanical research, focusing especially on work with a microscope. He led the field on research that studied fossils under the microscope, and was particularly interested in studying pollination among the higher plant species. His microscopic research led him to discover the nucleus of the cell (1831), which he observed in plant tissue and which he named. The presentation of this discovery was typical of much of Brown's work-he imbedded this discovery in a pamphlet which focused on the sexual organs of orchids.

A Dedicated Botanist

In his personal life, Brown was known as a witty, yet quiet man who associated mainly with his peers. He never married and lived a home bequeathed to him by Banks until his death. Because of Brown's broad range of knowledge that would have been difficult to synthesize, his published work often suggested questions and possibilities for further research. Darwin, a peer of Brown's remarked on the "minuteness of [Brown's] observations and their perfect accuracy". Darwin claimed that when Brown died, much of his knowledge "died with him, owing to his excessive fear of never making a mistake." Brown appeared to have been untroubled by financial worries during his lifetime, and turned down three professorships. He continued his lifelong passion for botany and hiked to the top of a Scottish mountain (where he had studied plants 60 years earlier) five years before his death. Brown died in London on June 10, 1858.

Further Reading

• Collier's Encyclopedia, edited by William D. Halsey, Macmillan, 1990.
• Columbia Encyclopedia, 5th edition, 1993.
• Dictionary of Scientific Biography, edited by Charles Coulston Gillispie, Charles Scribner's Sons, 1973.
• Merriam-Webster's Biographical Dictionary, 1995.
• World Who's Who in Science, edited by Allen G. Debus, Marquis Who's Who, 1968.
• Economist, October 3, 1992.
• Science News, May 4, 1991.
• Scientific American, August, 1991.