George Gammie was the son of the head gardener (later deputy superintendent) at the Bengal Government Cinchona Plantation at Mungpoo, near Darjeeling. It was here that the young Gammie's interest in plants was first stimulated. Gammie went on to carry out botanical work in India while officially employed as an assistant in the Cinchona Department between 1881 and 1899. His interest in botany having been recognised, Gammie was put in charge of the Lloyd Botanic Garden in Darjeeling in the early 1890s. At this time he also made a botanical tour of Sikkim and in 1894 collected plants in the Lakhimpur district of Assam. He was then invited to take up curatorship of the herbarium of the Calcutta Royal Botanic Gardens, where he stayed from 1894-1896. He then collected in the north-western Himalayas.

Gammie was transferred to the service of the Government of Bombay in 1899, being appointed Lecturer in Botany and Agriculture at the Poona College of Science. He was also put in charge of the Botanical Survey of the Bombay Presidency and from 1904-1908 served as Economic Botanist to the Government of Bombay. After entering the service of the Bombay Government, Gammie was afforded much time to make extensive collections in western India. Gammie's final posting was as Imperial Cotton Specialist, which role took him up to his retirement in 1919. His published work reflected his interest in both systematic and economic botany. Gammie's obituary in the Proceedings of the Linnean Society describes him as "an unassertive, genial, slow-moving man of massive build and fair complexion, welcome in any company." He was elected a Fellow of the Linnean Society in 1899.

Sources:
A.T.G., 1936, Proceedings of the Linnean Society of London, 148(4): 207-208.