A chance observation " thoroughly aroused " Darwin's attention to a surprising decrease in vigour of the offspring of " Linaria vulgaris " following only one instance of self-fertilisation, and after eleven years of experimental work he published " The Effects of Cross and Self Fertilisation in the Vegetable Kingdom " in 1876 as " a complement to the'Fertilisation of Orchids,'because it shows how important are the results of cross-fertilisation which are ensured by the mechanisms described in that book ."
