DARWIN'S WORK ON THE MOVEMENTS OF PLANTS
BY FRANCIS DARWIN
Honorary Fellow of Christ's College, Cambridge.
MY father's interest in plants was of two kinds, which may be roughly distinguished as Evolutionary and Physiological. Thus in his purely evolutionary work, for instance in The Origin of Species and in his book on Variation under Domestication, plants as well as animals served as material for his generalisations. He was largely dependent on the work of others for the facts used in the evolutionary work, and despised himself for belonging to the "blessed gang" of compilers. And he correspondingly rejoiced in the employment of his wonderful power of observation in the physiological problems which occupied so much of his later life. But inasmuch as he felt evolution to be his life's work, he regarded himself as something of an idler in observing climbing plants, insectivorous plants, orchids, etc. In this physiological work he was to a large extent urged on by his passionate desire to understand the machinery of all living things. But though it is true that he worked at physiological problems in the naturalist's spirit of curiosity, yet there was always present to him the bearing of his facts on the problem of evolution. His interests, physiological and evolutionary, were indeed so interwoven that they cannot be sharply separated. Thus his original interest in the fertilisation of flowers was evolutionary. "I was led 1," he says, "to attend to the cross-fertilisation of flowers by the aid of insects, from having come to the conclusion in my speculations on the origin of species, that crossing played an important part in keeping specific forms constant." In the same way the value of his experimental work on heterostyled plants crystalised out in his mind into the conclusion that the product of illegitimate unions are equivalent to hybrids -- a conclusion of the greatest interest from an evolutionary point of view. And again his work Cross and Self Fertilisation may be condensed to a point of view of great importance in reference to the meaning and origin of sexual reproduction 2.____________________