Darwin From Insectivorous Plants To Worms - Cross and Self Fertilisation

Cross and Self Fertilisation

With Variation at the printers and with his old essay on The Movements and Habits of Climbing Plants due out in November 1875 with "illustrations... drawn by my son, George", Darwin wrote The Effects of Cross and Self Fertilisation in the Vegetable Kingdom. This drew on a painstaking series of experiments, protecting the plants from insects and controlling the pollination of flowers, counting the seeds and checking them for fertility, repeated for up to ten generations with detailed records kept at every stage.

Darwin tabulated the results, Galton checked his statistics, and they found the crossed plants significantly superior to self-fertilised ones in height, weight, vigour and fertility. The same principle would apply to people, and though the attempt to get a question on the census had failed, George analysed data from lunatic asylums and the Pall Mall Gazette which Darwin cited as showing a small effect produced by first-cousin marriages.

While Emma ensured that he took short breaks, Darwin pressed on with work as "my sole pleasure in life" and finished the first draft of Fertilisation in May 1876, promptly going on to a revision of Orchids.