He then studied Sciences (with a focus upon Geology) at King's College London graduating BSc in 1912 and gaining a doctorate (DSc) in 1919. In 1922 he left Britain to take up a teaching role in the Danish-owned island of St Croix (now part of the US Virgin Islands). In 1923 he became Professor of Botany at the Imperial College of Tropical Agriculture in Trinidad and Tobago. In 1926 he also became Director of the Cotton Research Station in Trinidad, continuing in this role until 1935. In 1940 he moved to Peru as Director of the Institute of Genetics within the National Agricultural Society of Peru.
He returned to Britain in 1949 as a Reader in Botany at the University of Manchester being made the George Harrison Professor of Botany at the University of Manchester the following year, 1950, and retaining this post until 1958, when he was subsequently made an emeritus professor.
He was made a Fellow of the Royal Society in 1943. In 1951 he was elected a Fellow of the Royal Society of Edinburgh. His proposers were Claude Wardlaw, Herbert Graham Cannon, William Black and William Robb.
He died in Snainton on 8 November 1982.
- The Genetics of Cotton (1939)
He married Emily Wilson Cameron in 1915. They had two daughters but divorced and in 1934 he married Olive Sylvia Atteck, from a wealthy Trinidad family. Their son became a Professor of Child Health in the West Indies. Another son of his is psychologist Richard Lynn.
- Biographical Index of Former Fellows of the Royal Society of Edinburgh 1783–2002 (PDF). The Royal Society of Edinburgh. July 2006. ISBN 0 902 198 84 X.
- ‘HARLAND, Sydney Cross’, Who Was Who, A & C Black, an imprint of Bloomsbury Publishing plc, 1920–2016
- Oxford Dictionary of National Biography, S. Harland
- Hutchinson, J. (1984). "Sydney Cross Harland. 19 July 1891 – 8 November 1982". Biographical Memoirs of Fellows of the Royal Society. 30: 298. doi:10.1098/rsbm.1984.0011.