Isaac Bayley Balfour was born in Edinburgh on 31 March 1853. He was the son of the Professor of Botany at Edinburgh University, John Hutton Balfour (1808-1884). Balfour was educated at Edinburgh Academy and then he studied at Edinburgh University where he was awarded the degrees of B.Sc. in 1873, and D.Sc. in 1875. He also studied abroad at Strasbourg and Wurzburg. He participated in expeditions to Rodriguez in 1874, Socotra in 1880, and Japan and China in 1909-1910. Balfour was Regius Professor of Botany at Glasgow University between 1879 and 1884, then Sherardian Professor of Botany at the University of Oxford, and Fellow of Magdalen College, from 1884 to 1888. From 1888, he was Professor of Botany at Edinburgh University, Regius Keeper of the Royal Botanic Garden in Edinburgh, and the King's Botanist in Scotland. During his Keepership of the Garden, the whole establishment underwent re-organisation, buildings and gardens. He was knighted in 1920. Sir Isaac Bayley Balfour died at Haslemere on 30 November 1922.