At the start of 1863, Charles Darwin was actively working on the manuscript of The variation of animals and plants under domestication, anticipating with excitement the construction of a hothouse to accommodate his increasingly varied botanical experiments, and continuing a massive scientific correspondence. Six months later the volume of his correspondence dropped markedly, reflecting a decline in his already weak health. Although Darwin worried about the effect of the quarrels on public perceptions, his theory was gathering support in influential scientific circles. He struggled with leaf angles, fractions, diagrams, and shoot dissections.

1862 was a particularly productive year for Darwin. This was not only the case in his published output (two botanical papers and a book on the pollination mechanisms of orchids), but more particularly in the extent and breadth of the botanical experiments he carried out. While many of these remained unpublished for several years, they formed the foundation of numerous later publications. The promotion of his theory of natural selection also continued: Darwin’s own works expanded on it, Thomas Henry Huxley gave lectures about it, and Henry Walter Bates invoked it to explain mimicry in butterflies.