Francis Darwin

“ Of the book which I have been using as my text, namely, Vegetable Staticks, Sachs says: "It was the first comprehensive work the world had seen which was devoted to the nutrition of plants and the movement of their sap....Hales had the art of making plants reveal themselves. By experiments carefully planned and cunningly carried out he forced them to betray the energies hidden in their apparently inactive bodies [1] ." These words, spoken by a great physiologist of our day, form a fitting tribute to one who is justly described as the father of physiology. ”

“ After reading the 'Journal' of 1845 we come back with a sense of surprise to the Manuscript Sketch of 1844, where his theory of evolution by means of natural selection is so completely given. Even in the note-book filled between July 1837 and February 1838 the views on evolution are striking in their completeness; thus he clearly believed in the common origin of animals and plants. ”

“ Thus the weak, straggling stem of a climbing plant gets all the advantages gained by the solid, column-like tree-trunk. If we apply this test—which is the most economical plan of climbing, twining, or leaf climbing—we see at once that a plant which climbs by seizing wastes far less material than one which twines. Thus a kidney-bean, which had climbed up a stick to a height of two feet, when unwound from its support was found to be three feet in length, whereas a pea which had climbed up two feet by its tendrils was hardly longer than the height reached. ”

“ The work on barnacles, besides being a complete and original study on an imperfectly known and misinterpreted group of animals, was of importance, inasmuch as it may be said to have completed Darwin's education as a naturalist. It gave him an insight into taxonomy and morphology, which served him well in writing the 'Origin of Species,' and it taught him, as Mr. Huxley has said, to understand in this branch of knowledge what amount of speculative strain his facts would bear — an experience he had already gone through during the voyage of the Beagle in the case of geology. ”

“ Here, then, is a most curious power possessed by the shoots of twining plants, which is worth inquiring further into, both as regards the way in which the movement is produced, and as to how it can be of any service to the plant. Questions are often asked in gardening periodicals as to how hops or other climbing plants always manage to grow precisely in the direction in which they will find a support. This fact has surprised many observers, who have supposed that climbing plants have some occult sense by which they discover the whereabouts of the stick up which they subsequently climb. ”

“ If the character of his working life is to be understood, the conditions of ill-health under which he worked should never be forgotten. He bore his illness with such patience that even those most intimate with him hardly realised the amount of his habitual sufferings. But it is no exaggeration to say that for nearly forty years he did not know one day of the health of ordinary men, and that his life was one long struggle against the weariness and strain of sickness. ”

“ This may remind us of Herbert Spencer's words: "Thus the essential characteristic of living organic matter, is that it unites this large quantity of contained motion with a degree of cohesion that permits temporary fixity of arrangement," First Principles, § 103. With regard to the way in which plants absorb and fix the "air" which he finds in their tissues, Hales is not clear; he does not in any way distinguish between respiration and assimilation. But as I have already said he definitely asserts that plants draw "sublimed and exalted food" from the air. ”

“ As plants have no muscles, all their movements are produced by unequal growth; that is, by one half of an organ growing in length quicker than the opposite half. Now, the difference between the growth of a twining plant which bends over to one side and an ordinary plant which grows straight up in the air lies in this, that in the upright shoot the growth is nearly equal on all sides at once, whereas the twining plant is always growing much quicker on one side than the other. ”

“ He wrote in November 1836: ‘Among the great scientific men, no one has been nearly so friendly and kind as Lyell. ... You cannot imagine how good-naturedly he entered into all my plans.’ Lyell received the theory of coral reefs with enthusiasm, although its adoption necessitated the destruction of his own views on the subject. It must have been a great encouragement to Darwin to find himself welcomed as a brother-geologist by such a man as Lyell, the value of whose work he had personally tested and learned to estimate in South America. ”

“ Hales says in relation to greenhouses, "it is certainly of as great importance to the life of the plants to discharge that infected rancid air by the admission of fresh, as it is to defend them from the extream cold of the outward air." ”

“ There are other facts of a different nature, which seem to show how difficult the problem is, and how delicately balanced is that part of the organization of the plant which is connected with the power of climbing. For instance, if we cut a branch of most shrubs, and put it in water, it goes on growing, apparently as healthily as ever. Indeed, the practice of making cuttings—where a cut-off branch or shoot develops roots and turns into a new plant—shows us that no serious injury is thus caused. But the twining organization is sensitive to such treatment. ”

“ The great feature of his Cambridge life was undoubtedly his friendship with Henslow, the professor of botany in the university. Henslow was a man courteous and placid outwardly, but at the same time unbending and full of vigour where principle was concerned, and fully worthy of the great love and respect that Darwin felt towards him. He was eminently well fitted to be a friend to undergraduates. ”

“ A hop-plant will supply a good example of the mode of growth of true twining plants. Let us imagine that we have a young hop-plant growing in a pot; we will suppose that it has no stick to twine up, and that its pot stands in some open place where there are no other plants to interfere with it. A long, thin shoot will grow out, and, not being strong enough to support itself in the upright position, will bend over to one side. ”

“ What Darwin himself believed to be the great flaw in the 1844 sketch was want of the ' principle of divergence ' (see Origin of Species 6th ed.) By those who are imbued with evolution as taught in the 'Origin of Species,' this 'principle of divergence will hardly be missed in reading the sketch of 1844; we seem unconsciously to assume the principle, although it is not given. In his later years Darwin had something of this feeling, for it became all but incredible to him that he should at first have overlooked it. ”

“ It is by looking to exceptions that the key to a problem is often found. It is the exceptions to general rules that often lead us to understand the meaning and origin of the rules themselves; and it is to such exceptions that any one who wants to work at climbing plants should turn. Now, it is a general rule that a climbing plant twines in the same way that it revolves. It seems an obvious thing that in the case of the rope model, if we swing the rope round our head in the direction of the hands of a watch, it must twine round the stick against which it strikes in the same direction. ”

“ Darwin always enjoyed experimental work far more than writing, and the pleasure of following out the brilliant discoveries which he made in the natural history of insectivorous plants was a relief and rest to him from the drier labour of preparing a second edition of the 'Descent of Man.'
Darwin's last publications were two papers of no great importance, read before the Linnean Society in the autumn of 1881. ”

“ The fact that leaf-and tendril-climbers have been developed out of twiners, and not vice versa, is a proof that climbing by leaves or tendrils is a more advantageous habit than twining; but we do not see why it should be so. If we inquire why any plant has become a climber, we shall see the reason. Light is a necessity for all green plants; and a plant which can climb is enabled to escape from the shadow of other plants with a far less waste of material than a forest tree, which only pushes its branches into the light by sheer growth. ”

“ It has been well said that one great service rendered by Darwin to science was the revival of teleology in a rational form, a form in which it is no longer opposed to, but 'wedded to morphology.' The knowledge of the manner in which the structures of living beings have become adapted to their various encfa gives a vigour to the study of the form and organisation of animals and plants, the importance of which can hardly be exaggerated. ”

“ Now, a revolving shoot may be more than two feet long, so that it might be detained in its swinging-round movements by a stick fixed into the ground at a distance of nearly two feet. There would then be a straight bit of stem leading from the roots of the plant, in a straight line to the stick up which it twines, so that an observer who knew nothing of the swinging-round movement might be pardoned for supposing that the plant had in some way perceived the stick and grown straight at it. This same power of swinging round slowly comes into play in the very act of climbing up a stick. ”

“ And it was to a great extent by his special botanical work that he wrought this cnange; for it was in botany that he showed in practice how powerful, for the study of adaptive structure, are the means of research which the ' Origin of Species ' has placed in our hands. It was work of this nature which occupied his later years; the subject-matter varied, but whether he investigated the fertilisation of flowers, the twining of steins, the movements of leaves, or the natural history of insectivorous plants, the character of the work remained the same. ”

“ Supposing that we have noticed the shoot, when it began to bend over, pointed toward the window—say a north window—and that, when we next look at it after some hours, it points into the room, that is to say, south, and again, north after another interval, we shall have discovered the curious fact that the hop-plant has a certain power of movement by which its shoot may sometimes point in one direction, sometimes in another. ”