Text-book of botany : morphological and physiological / by Julius Sachs ; translated and annotated by Alfred W. Bennett ; assisted by W.T. Thiselton Dyer.

Date:
1875
Catalogue details

Licence: Public Domain Mark

Credit: Text-book of botany : morphological and physiological / by Julius Sachs ; translated and annotated by Alfred W. Bennett ; assisted by W.T. Thiselton Dyer. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    802/880 (page 786)
    the movements of the compound leaves of Leguminosae, of many species of Oxalis, and of Marsilea. In the Leguminosae the common petiole is often attached to the stem by a larger contractile organ or ‘pu/uinus’; and in all the cases just named the petiolule of each leaflet possesses a similar organ. If, as in the bipinnate leaves of Mimosa, there are secondary common petioles, these are also attached to the primary petiole by contractile organs. These organs always consist of an axial fibro-vascular bundle surrounded by a thick layer of turgid parenchyma. The other parts of the leaves, the petioles as well as the lamina, are not spontaneously contractile, but the alterations in their length are caused by the curvatures of the organs at their base. The movement is either a curving upwards and downwardas in Phaseolus, Trifolium, Oxalis, and the common petioles of Mimosa, or is directed from behind and below in a forward and upward direction, as in the leaflets of Mimosa. (2) The phenomena known as Waking and Sleeping are exhibited with peculiar dis- tinctness in the leaves of Leguminosae and Oxalideae and of Marsilea, and are caused by the organs which also produce the spontaneous periodic movements’. They occur also in the leaves of many other plants as Scitamineae, where the lamina is attached to the petiole by a similar cylindrical contractile organ, as well as in many leaves (especially also in green cotyledons) the petiole and lamina of which do not possess a sharply differentiated prominent contractile organ; in these cases the movements of sleeping and waking are occasioned by the basal and apical portions of the petiole. It is not known whether these leaves are also endowed with automatic periodic motion. In all these green leaves the movement is caused principally by the alternation in the intensity of the light, and especially by that of the strongly refrangible rays1 2 3; every increase of intensity causing a movement in the direction of the diurnal position, every decrease one in the direction of the nocturnal position. In the diurnal position of these organs the leaves generally have their surfaces com- pletely unfolded and expanded flat; in the nocturnal position they are on the contrary folded up in different ways, being turned upwards, downwards, or sideways. The leaflets of Lotus, Trifolium, Vicia, and Lathyrus are, for example, folded upwards at night, those of Lupinus, Robinia, Glycyrrhiza, Glycine, Phaseolus, and Oxalis downwards; the com- mon petiole of Mimosa turns downwards at night, that of Phaseolus becomes erect; the leaflets of Mimosa and Tamarindus indie a3 turn laterally forwards and upwards in the dark, those of Tephrosia carabica backwards. When the petiole and other parts of the same leaf are contractile, the curvatures of the various motile parts may differ; thus, for example, the petiole of Phaseolus turns upwards in the evening, while the leaflets turn downwards; the petiole of Mimosa on the other hand turns downwards while the leaf- lets turn forwards and upwards, till they partially cover one another in an imbricate manner. As the periodic movement of leaves, and that of sleeping and waking must be distinguished from revolution caused by growth, which makes them unfold, so in flowers a distinction must be drawn—which is not always done4—between mere unfolding and the periodic movements of sleeping and waking. Petals which, after opening and remain- ing open for some time, simply fall off or wither (like those of Mirabilis, Cereus grandi- Jlorus, Helianthemum vulgare, &c.) are not included in this category. There are others however5 which last for some days and alternately open and close, usually in the evening and morning or on a change of weather, as e.g. those of Tulipa, Crocus, the potato, Oxalis, Mesembryanthemum, Ipomaea, Convolvulus, Hemerocallis, Portulaca, &c. The 1 [See Somnus Planlarum, P. Bremer, Linn. Amcen. Acad. iv. p. 333.—Ed.] 2 See Sachs, Bot. Zeit., 1857, p. 813. 3 See Meyen, Neues System der Pflanzen-Physiologie, vol. Ill, p. 476. 4 Compare Dutrochet, Mdmoires pour servir, 1837, vol. I, p. 469 el seq. 6 [See Linnaeus, Philosophia Botanica, ed. 1780, pp. 272-275; K. Fritzsch, On the Periodical Opening and Closing of Flowers, Journ. Hort. Soc. Lond. vol. VIII, 1853.—Ed.]