THE SENSITIVE PLANT.

Lake Wakatip Mail, Issue 1860, 26 February 1892, Page 4

THE SENSITIVE PLANT.

Who that know?, who that bai seen the eensitive plant, mimosa pudica, has not also remarked on the sensibility of its leaves ? The slightest touch suffices its leaflets to close upon their supports, the petiolules, and the petiole upon the stem. If we cut with scissors the extreme end of one leaflet, the others will immediately close in succession. De Candolle was in the habit of placing a drop ot water upon one of the leaflets of the sensitive plant, applying it with so much delicacy as to excite no movement whatever. But when he substituted for the water a drop of sulphuric acid, he observed that the leaflets closed, the petiolules as well as the petiole were lowered and submitted to its influence, and gradually all the leaves situated above the one touched had undergone the same fate. Without the leaves situated b dow participating in the movement. This irritation cle<vrly shows that the irritation is not local, but communicates itself gradually in the various elements of a leaf, and propagates itself similar'y from one leaf to another. During the time that these movements are in operation, it will be observed that the limb of the leaflet neither curves itself nor shrivels. In short, the contractile power res des at the point of insertion of the leafleti upou the petiolulep, these upon the common petiole, and these again upon the stem. These various points of insertion correspond with the very perceptible cylindrical cushions which during the season of rest swell below, while in the state of irritation they are distended above. The movement v/hich we provoke in the case of the sensitive plant manifests itself with much greater rapidity when irritated upon this cushion than in any other part of the plant. We have remarked that the more vigorous the sensitive plant is in its habit, the more susceptible '"sit; th) higher the temperature, the more promptly does it respond to the touch. We may observe besides that the Sensitive Plant can, up to a certain point get accustomed to the movement. Desfontaines, carrying a Sensitive Plaut in a carriage, observed that th* plant closed its leaflets, and all its leaves drooped 3s soon as the carriage to roll over the pavement, but by decrees it seemed to recover from its fright, become habituated, so to speak, to the movements, resumed its erect position, and its leaflets their full expansion. Deefantaines now caused the carriage to etop for a time. When it resumed its motion the flower responded by droppiug its leaves as before, but after a time they expanded again, and so continued during the remainder of the journey. These phenomena of irritability undor the influence of direct chemical or mechanical action the plant repeats of itself during the night. The Sensitive Plant closes its leaflets when the obscurity of night sets iD. —From Figuer's Vegetable World.