You may see a still faster movement if you carefully examine a twining tendril. Notice how the young tendrils of a sweet-pea are at first almost straight, growing out into the air (~see~ fig. 31). Now choose such a one for the experiment, and another like it which you do not touch, but keep to compare with the one on which you have experimented. Gently rub one side of the tendril with a small rough twig, and then leave it alone. You will see that in about five or ten minutes it has begun to curve, and in a quarter of an hour may have bent round completely. Such movement is more rapid than that in the ordinary growth, and this power of bending so quickly is one of the special characters of tendrils, and one that is very important in helping them to do their work for the plant and to seize on any support within reach as quickly as possible. [Illustration: Fig. 32. Leaves of Wood-sorrel; A in the day position, B “asleep” at night.] Then there are other movements, one of which you must have often observed in the “sleep” of plants. Many flowers and leaves close up and bend down at night, taking up their usual position again next day. This is not the same thing as the opening of buds, for it may occur again and again in the fully grown parts of plants. For example, you may mark certain leaves of wood-sorrel or common clover, and watch them close up at night and re-open in the morning many times. These movements are not very fast, and you cannot see the plant moving as you can see a kitten waving its tail, but the difference is only one of degree. [Illustration: Fig. 33. Leaf of Sensitive Plant in its usual position.] [Illustration: Fig. 34. Leaf of Sensitive Plant, leaflets at ~a~ beginning to close after being gently touched.] There are plants, however, which move so quickly that you can see them close up their leaves at once at the slightest touch. This is the case in the Sensitive Plant (fig. 33), and if you only tap one of its tiny leaflets with a straw, that pair of leaflets will immediately fold up, then the next pair, and the next, till the whole leaf has closed, when it drops quickly down (~see~ fig. 35), this movement only taking a moment. If the shock is great, all the leaves on the plant will close up instantly, and they move so quickly that you can hardly see them doing it. [Illustration: Fig. 35. Leaf of Sensitive Plant quite closed, and the leaf-stalk fallen, after being touched.] Some foreign plants swing their leaflets round slowly like the arms of a windmill, but we have not yet found out why they do this. Also in many flowers we find movement, and in flowers it is generally in relation to the insects which visit them. For example, some orchids shut up their big front petal with a sudden snap when an insect alights on it and shoot the astonished fly towards the middle of the flower.