Читать книгу Intelligence in Plants and Animals онлайн

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That a plant and an animal should secrete the same, or nearly the same, complex digestive fluid, adapted for a similar purpose, is a wonderful fact in physiology, but not more remarkable than the movements of a tentacle consequent upon an impulse received from its own gland, the movement at the bending place of the tentacle being always towards the centre of the leaf, and so it is with all the tentacles when their glands are excited by immersion in a suitable fluid. The short tentacles in the middle part of the disc, however, must be excepted, as these do not bend at all when thus excited. But when the motor impulse comes from one side of the disc, the surrounding tentacles, and even the short ones in the middle of the disc, all bend with precision towards the point of excitement, no matter where it may be located. This is in every way a remarkable phenomenon, for the leaf appears as if endowed with animal sense and intelligence. It is all the more remarkable when the motor impulse strikes the base of a tentacle obliquely to its flattened surface, for then the contraction of the cells must be restricted to one, two or a very few rows at one end, and different sides of the surrounding tentacles must be acted on that all may bend with precision to the point of excitement. The motor impulse, as it spreads from one or more glands across the disc, enters the bases of the surrounding tentacles, and instantly acts on the bending place, but does not first proceed up the tentacles to the glands, causing them to reflect back an impulse to their bases, although some influence is sent up to the glands, whereby their secretion is soon increased and rendered acid. The glands, being thus excited, send back some other influence, dependent neither on increased secretion nor on the inflection of the tentacles, which causes the protoplasm to aggregate in cell beneath cell. This maybe called a reflex action. How it differs from that which proceeds from the nerve-ganglion of an animal, if it differ at all, no one can say. It is probably the only known case of reflex action in the vegetable kingdom.