Henry Horatio Dixon FRS (19 May 1869, Dublin â 20 December 1953, Dublin) was a plant biologist and professor at Trinity College Dublin. Along with John Joly, he put forward the cohesion-tension theory of water and mineral movement in plants.
He was born in Dublin, the youngest of the seven sons of George Dixon, a soap manufacturer and Rebecca (nÊe Yeates) Dixon. He was educated at Rathmines School and Trinity College, Dublin. After studying in Bonn, Germany he in 1894 he was appointed assistant and later full Professor of Botany at Trinity. In 1906 he became Director of the Botanic gardens and in 1910 of the Herbarium also. He had a close working relationship with physicist John Joly and together they developed the cohesion theory of the ascent of sap.