Dixon, Henry Horatio (1869–1953)

Irish botanist, born in Dublin, whose research focused on cytology (the study of cells). Dixon developed the cohesion theory with the Irish geologist and physicist John Joly, which explained why sap and water can rise great heights to the tops of trees. He also observed that cosmic rays could have a mutagenic effect.

Dixon entered Trinity College, Dublin, in 1887, winning a scholarship to study classics. He later switched to natural science in which he graduated in 1891, the move largely due to the influence and encouragement of Joly.

Dixon was intrigued by experiments that showed that sap could rise even if cells in the stem were dead. He built various pieces of apparatus to demonstrate the great cohesive force that could be established in a bubble-free column of water locked in tree cells and drawn forward by evaporation at the leaves.