Collett was born in
Thetford,
Norfolk, the fourth son of Rev. W. Collett and his second wife Ellen Clarke née Bidwell, He studied at
Tonbridge School and at
Addiscombe Military Seminary. He joined the
Bengal Army on 8 June 1855, rising through the ranks to become a
lieutenant colonel in 1879. In the
Second Anglo-Afghan War (1878–80) he acted as
quartermaster general on the staff of
Frederick Roberts, 1st Earl Roberts. He was promoted colonel in 1884, made
KCB in 1891, and from 1892 to 1893 he commanded the
Peshawar district with the rank of
major-general. He retired from the army in 1893. Collett was a keen botanist, an interest that he developed when posted in 1878 in the
Kurram Valley. He studied and collected plants in Afghanistan, Algeria, Burma, the Canaries, Corsica, India, Java, and Spain. He was made a fellow of the
Linnean Society of London in 1879. He was one of the founding members of the Simla Naturalists' Society. At his death he was working on a book on the flora of
Simla, which was published posthumously as
Flora Simlensis (1902). His
herbarium collection was presented to the
Royal Botanic Gardens, Kew in London, England after his death. The plant species
Iris collettii was named after him in 1909. ==Notes==