473. Leaf-stalks and tendrils are adapted to their uses in climbing by a similar sensitiveness. The coiling of the leaf-stalk is in response to a kind of irritation produced by contact with the supporting body. This may be shown by gentle rubbing or prolonged pressure upon the upper face of the leaf-stalk, which is soon followed by a curvature. Tendrils are still more sensitive to contact or light friction. This causes the free end of the tendril to coil round the support, and the sensitiveness, propagated downward along the tendril, causes that side of it to become less turgescent or the opposite side more so, thus throwing the tendril into coils. This shortening draws the plant up to the support. Tendrils which have not laid hold will at length commonly coil spontaneously, in a simple coil, from the free apex downward. In Sicyos, Echinocystis, and the above mentioned Passion-flowers (471), the tendril is so sensitive, under a high summer temperature, that it will curve and coil promptly after one or two light strokes by the hand. [Illustration: Fig. 491. Portion of stem and leaves of Telegraph-plant (Desmodium gyrans), almost of natural size.] 474. Among spontaneous movements the most singular are those of Desmodium gyrans of India, sometimes called Telegraph-plant, which is cultivated on account of this action. Of its three leaflets, the larger (terminal) one moves only by drooping at nightfall and rising with the dawn. But its two small lateral leaflets, when in a congenial high temperature, by day and by night move upward and downward in a succession of jerks, stopping occasionally, as if to recover from exhaustion. In most plant-movements some obviously useful purpose is subserved: this of Desmodium gyrans is a riddle. 475. =Movements in Flowers= are very various. The most remarkable are in some way connected with fertilization (Sect. XIII.). Some occur under irritation: the stamens of Barberry start forward when touched at the base inside: those of many polyandrous flowers (of Sparmannia very strikingly) spread outwardly when lightly brushed: the two lips or lobes of the stigma in Mimulus close after a touch. Some are automatic and are connected with dichogamy (339): the style of Sabbatia and of large-flowered species of Epilobium bends over strongly to one side or turns downward when the blossom opens, but slowly erects itself a day or two later. 476. =Extraordinary Movements connected with Capture of Insects.= The most striking cases are those of Drosera and Dionæa; for an account of which see "How Plants Behave," and Goodale's "Physiological Botany."