Henry A. Cummins, son of William Jackson Cummins and his wife Elizabeth Henrietta, born Poole, was educated at Queens's College, Cork, Ireland (later University College, National University of Ireland), and later qualified as Doctor of Medicine (MD) at the Royal University of Ireland. As a member of the Royal Army Medical Corps he served in military expeditions to Sikkim (in north-east India, bordering on east Nepal) in 1888, and Ashanti (Gold Coast, now Ghana) in 1895-1896. The first of these expeditions enabled him to describe a new species of toothwort, a parasitic plant, in 'Description of a new Lathraea from the Eastern Himalaya' (Journal of the Asiatic Society of Bengal, 1896). The second expedition led to a paper on 'Botany of the Ashanti expedition', in Kew Bulletin (1898). His wider interests are indicated by two further papers at this time: 'A theory of vegetable antitoxins' (Proceedings of the Asiatic Society of Bengal, 1897), and 'On the food of Uropoda' (a group of crustaceans belonging to the class Malacostraca; Journal of the Linnean Society (Zoology), 1898).
During the Anglo-Boer War (1899-1902) Cummins served in South Africa, where he earned the Queen's Medal (4 clasps) and in 1900 was invested as a Companion of St Michael and St George (CMG). Soon after his arrival he wrote on 'Enteric fever in South Africa' (1900) and 'The sterilisation of enteric stools' (1901) in the British Medical Journal. His 'Meteorological notes on South Africa' appeared in the Quaterly Journal of the Royal Meteorological Society (Vol. 28, pp. 105-106) in 1902. It gives an account of his experiences in South Africa, including the violent thunderstorms that much impressed him. In 1909 he collaborated with D. Prain in describing the family of trees Loganiaceae for the Flora Capensis (Vol. 4(1), pp. 1036-1055).
Cummins was recalled for military service in World War I (1914-1918). He was a Fellow of the Linnaean Society of London and ended his professional career as professor of botany at the University College, Cork. Some of his later papers dealt with the fungi found in milk (1929) and in butter (1930), and fungi of the genus Phoma (1932). In 1894 he married Ethel Percy Hall, with whom he had five children.