Ipecacuanha plant from Hooker. He left for India in March and reached Calcutta on 11 April 1866. India King was initially appointed to the General Hospital before transferring to the Medical College Hospital where he was made house surgeon. He fell ill with pneumonia and it was suggested that he transfer to a drier climate. He was posted to Agra on 4 September and was attached to the 41st Bengal Infantry. He moved to Mathura in January 1867. Bouts of illness continued and it was suggested that he should move to central India. He was posted to Guna in February 1867, taking charge of the Central India Horse. The next year he moved to Rajputana with stints at Deoli, Mount Abu and Jodhpur before moving to the Botanic Garden at Saharanpur. At the end of 1869, as his term was ending at Saharanpur, he was invited to join the Forest Department as an Assistant Conservator. In his postings in India, he worked during his leisure time on its plants, making a study of the famine plants. He also made an ornithological survey of Guna. The posting in Dehra Dun gave him more time for study. King found that the forests of the Doon were being destroyed with a system of bribery and corruption within the Forest Department. King worked to eliminate the corrupt officials. In January 1871 King moved to the Kumaon Forest Division and prepared a report on the forests of Ranikhet. He also contributed to the botanical sections of the Gazetteers. It was recommend that he be made a permanent Deputy Conservator. In 1869, the Superintendent of the Royal Botanic Garden, Calcutta, Thomas Anderson, fell ill (left for Europe and died in 1870) and in 1871, the Secretary of State for India selected King as a successor. King took up the position and was also a Professor of Botany in the Medical College of Bengal. King was faced by the destruction wrought by two cyclones in 1864 and 1867. King was also involved in matters associated with tea and cinchona cultivation. While on an official visit to the Nilgiris in July 1872, he developed symptoms of pulmonary phthisis(tuberculosis). He was treated in Coonoor before moving to Europe. He spent a year in the Riviera and returned to Calcutta to resume duties in November 1873. King restructured the Calcutta Botanical Gardens, raising the level of the ground, creating ponds