. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. 376 VEGETABLE petioles, as in tlie Sensitive plant, they may be bent inwards towards each other, while the common petiole is bent downwards. Mimosa sensitiva and pudica (fig. 657), commonly called sensitive plants, display these movements of their leaves in a remarkable degree, not only under the influence of light and darkness, but also under mechanical and other stimuli. They have bipinnate leaves with four partial petioles pro- ceeding from a common r
. A Manual of botany : being an introduction to the study of the structure, physiology, and classification of plants . Botany. 376 VEGETABLE petioles, as in tlie Sensitive plant, they may be bent inwards towards each other, while the common petiole is bent downwards. Mimosa sensitiva and pudica (fig. 657), commonly called sensitive plants, display these movements of their leaves in a remarkable degree, not only under the influence of light and darkness, but also under mechanical and other stimuli. They have bipinnate leaves with four partial petioles pro- ceeding from a common rachis, and each of the petioles is furnished with nume- rous pairs of leaflets (about twenty), which are expanded horizontally during the day. During darkness, or when touched or irritated in any way, each leaflet moves upwards towards its feUow of the opposite side, which in its turn I * rises up, so that their upper surfaces Fi& 657. come into contact. When the movement commences at the apex of the leaf it usually proceeds downwards to the base, and thence may be communicated to the leaflets of the next partial petiole, and ultimately to the common petiole, which falls down towards the stem. The partial petioles then converge towards each other, and have a tendency to become parallel to the common petiole, at the extremity of which they are suspended. When the plant is shaken, as by the wind, all the leaflets close simultaneously, and the petioles drop together. If, however, the agitation is long continued, the plant seems as it were to become accustomed to the shock, and the leaflets will expand again. The stem itself is not concerned in the movements. It may be cut and wounded cautiously without causing any change in the leaves, and a portion of it may be removed with a leaf attached and still remaining expanded. If, however, a mineral acid is applied to the stem, after some time the petioles will fall and the leaflets collapse—the leaves perishing with the stem which
Size: 1492px × 1674px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
