The second edition of Darwin's The various contrivances by which British and foreign orchids are fertilised by insects, and the good effects of intercrossing (Orchids) was published in January 1877 (Publishers’ Circular, 1 February 1877, p. 93). The first edition had been published in 1862; it was popular with botanists, but sold slowly (Freeman 1977). The text of the second edition was considerably altered, and incorporated a paper published by Darwin in Annals and Magazine of Natural History in 1869 (‘Fertilization of orchids’). The material in this paper also appeared in the French translation of Orchids (Rérolle trans. 1870). Darwin had worked on the second edition from May 1876, in the intervals of his work on Cross and self fertilisation; he described it as ‘much labour’ (Correspondence vol. 24, Appendix II). His work involved new observations (ibid., letter to W. T. Thiselton-Dyer, 3 August 1876), and new references, and Darwin wrote to Asa Gray, ‘I have had to cut up the book immensely’ (ibid., letter to Asa Gray, 9 August 1876). The manuscript and corrected text were sent to the printers in early October (ibid., letter to William Clowes & Sons, 7 October [1876]). Francis Darwin, recovering from the death of his wife, Amy, helped to correct the proofs (ibid., letter to Francis Darwin, 8 October [1876]). The book was stereotyped for the US edition, published by Appleton, immediately (ibid., letter to R. F. Cooke, 16 September 1876); Darwin had sent Asa Gray proof-sheets so that he could write an early review (ibid., letter to Asa Gray, 27 November 1876).

The different forms of flowers on plants of the same species (Forms of flowers) was published on 9 July 1877 (Freeman 1977). Much of the book was taken up by updated versions of Darwin's earlier published papers on heterostyly, namely, ‘Dimorphic condition in Primula’, ‘Two forms in species of Linum’, ‘Three forms of Lythrum salicaria’, ‘Illegitimate offspring of dimorphic and trimorphic plants’, and ‘Specific difference in Primula’. Darwin started work on the book in November 1876 (Correspondence vol. 24, Appendix II), and sent the manuscript to Murray on 11 April 1877 (letter to R. F. Cooke, 11 April 1877). Publication was delayed by lack of paper and the need to make stereotype plates for Appleton (letter from R. F. Cooke, 29 June 1877).