In the same way the characteristic element in what is done by memory, or by that “unconscious memory” [51b] known as habit, is the association of a
chain of thoughts or actions each calling forth the next.
What I wish to insist on is, that the process I have called action-by-signal is of the same type as action-by-association, and therefore allied to habit and memory. The plants alive to-day are the successful ones who have inherited from successful ancestors the power of curving in certain ways, when, by accidental deviations from their normal attitude, some change of pressure is produced in their protoplasm. With the pianist the playing of A has become tied to, entangled or associated with, the playing of B, so that the striking of note A has grown to be a signal to the muscles to strike B. Similarly in the plant, the act of bending has become tied to, entangled or associated with, that change in the protoplasm due to the altered position. There is no mechanical necessity that B should follow A in the tune; the sequence is owing to the path built by habit in the man’s brain. And this is equally true of the plant, in which an hereditary habit has been built up in a brain-like root-tip.
The capacities of plants of which I have spoken have been compared to instincts, and if I prefer to call them reflexes it is because instinct is generally applied to actions with something of an undoubted mental basis. I do not necessarily wish it to be inferred that there can be nothing in plants which may possibly be construed as the germ of consciousness—nothing psychic, to use a convenient term; but it is clearly our duty to explain the facts, if possible, without assuming a psychological
resemblance between plants and human beings, lest we go astray into anthropomorphism or sentimentality, and sin against the law of parsimony, which forbids us to assume the action of higher causes when lower will suffice.
The problem is clearly one for treatment by evolutionary method—for instance, by applying the principle of continuity. [53a] Man is developed from an ovum, and since man has consciousness it is allowable to suppose that the speck of protoplasm from which he develops has a quality which can grow into consciousness, and, by analogy, that other protoplasmic bodies, for instance those found in plants, have at least the ghosts of similar qualities. But the principle of continuity may be used the other way up; it may be argued that if a lump of protoplasm can perform the essential functions of a living thing, to all appearances without consciousness, the supposed value of consciousness in Man is an illusion. This is the doctrine of animal automatism so brilliantly treated by Huxley. [53b] He is chiefly concerned with the value of consciousness to an organism—a question into which I cannot enter. What concerns us now is, that however we use the doctrine of continuity, it gives support to belief in a psychic element in plants. All I contend for at the moment is, that there is nothing unscientific in classing animals and plants together from a psychological standpoint. For this contention I may quote a well-known psychologist, Dr. James Ward, [53c]
who concludes that mind “is always implicated in life.” He remarks, too (ibid. p. 287): “It would be hardly going too far to say that Aristotle’s conception of a plant-soul . . . is tenable even to-day, at least as tenable as any such notion can be at a time when souls are out of fashion.”
This is a path of inquiry I am quite incapable of pursuing. It would be safer for me to rest contented with asserting that plants are vegetable automata, as some philosophers are content to make an automaton of Man. But I am not satisfied with this resting-place. And I hope that other biologists will not be satisfied with a point of view in which consciousness is no more than a bye-product of automatic action, and that they will in time gain a definite conception of the value of consciousness in the economy of living organisms. Nor can I doubt that the facts discussed in these pages must contribute to the foundation of this wider psychological outlook.
IV
A LANE IN THE COTSWOLDS
Early in May I walked up from the valley to the extreme rim of the Cotswolds, just above our house. The lower country is all pasture, where we can wander at will, and delight in the many beautiful trees: the fresh green elms, the vernal yellow of the oak (which lingers in varying degrees behind some of its companions, but does not deserve Tolstoy’s epithet ‘maussade’), and the grey anatomy of the timid ash, whose black buds are still getting up their courage. We do not owe the trees in the meadows to landowners with a taste for natural beauty, but to the cattle that must have shade.