In August 1873, Darwin had ‘a fit’, in which he temporarily lost his memory and could not move. He recovered, and busied himself in work on the cross- and self-fertilization of plants. Published in 1876, Effects of Cross and Self Fertilisation in the Vegetable Kingdom provided ample proof of his belief that cross-fertilized plants produced vigorous off-spring better placed to survive. Co-incidentally, about this time, his thoughts lingered towards his own family, with his seven children grown up and yet still no grandchildren.
Charles Darwin, The Effects of Cross and Self Fertilisation in the Vegetable Kingdom. London: John Murray, 1876. Leith Storage 9FFB D
In July 1877, Darwin and his son Francis collated various papers on heterostyled flowers (with styles of differing length, e.g. the primrose) which had been published previously by the Linnean Society. He believed Different Forms of Flowers – one of his most technical – was ‘very important, as bearing on the sterility of hybrids’ (Autobiography). It also validated his thoughts, expressed to Huxley: ‘Plants are splendid for making one believe in Natural Selection, as will and consciousness are excluded.’ The book was dedicated to Asa Gray, the American botanist.
____, The Different Forms of Flowers on Plants of the Same Species. London: John Murray, 1877. Science F3D
Darwin’s last botanical publication appeared in 1880, in a print run of 3,000. It was The Power of Movement in Plants, a continuation of his Movements and Habits of Climbing Plants. By investigating the mechanical cause of bending, Darwin revealed that plants are responsive to stimulation and have a high degree of sensitivity. Although his home-based experimental techniques were contested by the German botanist Julius von Sachs, his research held up, eventually leading to the science of growth hormones in plants.
____, The Power of Movement in Plants. London: John Murray, 1880. Science F3D
A true gardener at heart, Darwin was fascinated by worms, believing that they had a modicum of intelligence. He fed them (cabbage was a favourite), observed their skill at pulling leaves into their burrows, and devised ways of measuring worm activity. Although seemingly on an insignificant topic, Formation was a best-seller, when published in October 1881. The work also validated Darwin’s own belief in ‘small agencies and their accumulated effects’ over time, a lesson he had first learnt when reading Lyell’s Principles on board the Beagle. This was his last book; he died on the 19 April 1882.
____, The Formation of Vegetable Mould, through the Action of Worms. London: John Murray, 1881. Leith Storage GOQD