Volume 12 of The Correspondence of Charles Darwin provides the full authoritative texts of all known and available letters to and from Charles Darwin. The letters are accompanied by detailed explanatory footnotes and relevant supplementary materials, offering unparalleled insights into Darwin's experiments, thoughts, friendships, and family life. Volume 12 of this continuing series contains letters from 1864, when Darwin, despite continuing illness, was carrying out botanical experiments and working on his book, The Variation of Plants and Animals Under Domestication.