Butler took an initial interest in botany thanks to
Marcus Hartog, a Professor of Natural History. Hartog was researching
Saprolegnia a
genus of fungus-like
water moulds and Butler learnt techniques of study which he later applied to the related genus
Pythium. He went to Paris, Antibes, Freiburg, and Kew, spending time in the
Jardin des Plantes in Paris in the laboratory of mycologist
Philippe Édouard Léon Van Tieghem. In 1900, at the recommendation of the
Royal Botanic Gardens, Kew, he was appointed as the first Cryptogamic Botanist to the Government of India at
Calcutta. In 1902, Butler was transferred to
Dehra Dun under the Imperial Agricultural Department. During a visit to
Coorg he studied
spike disease of
sandalwood which was later studied by
L. C. Coleman, the Government Botanist in the
state of Mysore. In 1905 he became Imperial Mycologist at the
Imperial Agricultural Research Institute at
Pusa. He published a monograph of the Indian wheat
rusts in 1906 and his research on
Pythium in 1907. In 1918 he produced "Fungi and diseases in plants", which became a standard reference work for tropical plant pathologists. Between 1910 and 1912 Butler additionally held the office of Director and Principal at the Agricultural College in Pusa. In 1921 his services to India were recognised and he was awarded the
Order of the Indian Empire. == Career in England ==