Sir Francis "Frank" Darwin, F.R.S. (August 16, 1848 - 19 September 1925), a son of the British naturalist Charles Darwin, followed his father into botany.
Francis Darwin was born in Down House, Downe, Kent in 1848. He was the third son and seventh child of Charles Darwin and his wife Emma.
Darwin went to Trinity College, Cambridge, at first studying mathematics, then changing to natural sciences, graduating in 1870. He then went to study medicine at St George's Medical School, London, earning an MB in 1875, but did not practice medicine.
Darwin was married three times and widowed twice. First he married Amy Ruck in 1874, but she died in 1876 four days after the birth of their son Bernard Darwin, who was later to become a golf writer. He remarried Ellen Crofts and they had a daughter Frances Crofts Darwin (1886-1960), a poet who married the poet Francis Cornford and became known under her married name. Ellen died in 1903. His third wife was Florence Henrietta Fisher, widow of Frederic William Maitland, whom he married in 1913, the year in which he was knighted. Her sister Adeline Fisher was the first wife of Darwin's second cousin once removed Ralph Vaughan Williams.
Francis Darwin worked with his father on experiments dealing with plant movement, specifically phototropism and they co-authored The Power of Movement in Plants (1880). Their experiments showed that the coleoptile of a young grass seedling directs its growth toward the light by comparing the responses of seedlings with covered and uncovered coleoptiles. These observations would later lead to the discovery of auxin.
Darwin was elected a Fellow of the Royal Society on June 8, 1882, the same year in which his father died. Darwin edited The Autobiography of Charles Darwin (1887), and produced some books of letters from the correspondence of Charles Darwin; The Life and Letters of Charles Darwin (1887) and More Letters of Charles Darwin (1905). He also edited Thomas Huxley's On the Reception of the Origin of Species (1887).