These are letters and papers relating to North America chiefly from the official correspondence of the Gardens and the correspondence of its two directors, Sir William Jackson Hooker and Sir Joseph Dalton Hooker. There are 2 reels of letters from Asa Gray to the Hookers, in addition to other Gray letters elsewhere in the collection. A few letters (1787) from Americans to William Forsyth, superintendent of the Royal Gardens of St. James' and Kensington.

There is correspondence concerning geology, botany, natural history, natural selection, evolution, British science and scientists, and other scientific topics. Most of the letters are written by Lyell, with a very few items by others.