Joseph Dalton Hooker
Botanist. Worked chiefly on taxonomy and plant geography. Son of William Jackson Hooker. Friend and confidant of CD. Accompanied James Clark Ross on his Antarctic expedition, 1839–43, and published the botanical results of the voyage. Appointed palaeobotanist to the Geological Survey of Great Britain, 1846. Travelled in the Himalayas, 1847–9. Assistant director, Royal Botanic Gardens, Kew, 1855–65; director, 1865–85. Knighted, 1877. FRS 1847.
For more on Joseph Hooker and the 1400 letters he exchanged with Darwin over forty years, see https://www.darwinproject.ac.uk/joseph-dalton-hooker