CD had sent proof-sheets of Climbing plants to Carus in October 1875 (see letter to J. V. Carus, 14 October [1875]). The German translation was published in 1876 (Carus trans. 1876b).
Gray’s letter has not been found. The page numbers refer to Climbing plants 2d ed. Passiflora acerifolia (a synonym of Passiflora adenopoda) and Passiflora sicyoides are species of passion-flower.
Kotte Autographs (dealers) (2012) (letter); Staatsbibliothek zu Berlin – Preußischer Kulturbesitz (Slg. Darmstaedter Lc 1859: Darwin, Charles, Bl. 70) (copy of letter and original of enclosure)