MOVEMENT. Several modes of movement are manifeste?I in plants and plant organs. SOIlle of the lower forms (bacteria, and fungi) exhibit movements of locomotion in cer tain stages, swimming freely in the water in which they are found. The same is true of the zoospores and conjugating sexual cells (gametes) of many plants which themselves arc not motile. Also, the phismodia of slime molds show a peettliar thtwing of the protoplasm which results in motion from one place on the substratum to another. This is called anneboid movement. An other kind of movement often met with in plants is the na)vement. This is shown by the awns of certain grasses and other fruits (Fig. 1.), by the valves of many seed-pods ( Fig. 2.), by the teeth of the peristome of MOSS capsules, and by the elaters of liverworts, horsetails (Equisetum), etc. It is a non having no connection whatever with the vitality of the parts, being due merely to equal swelling or shrinkage warping) of the different tissues by reason of their unequal absorption or loss of water; and this depends on the like composition of the terial of the cell walls.
From a physiological point Of perhaps the most important form of plant movement is that exhibited and forward. while the whole leaf sinks (Fig. 3). If a shock be given to one pinwale, the ance there act up. if severe e gh, is propagated to other parts of the same leaf and even to other leaves. Almost any portion of the plant can receive a stimulus in this way and pass it. on to
other regions. The organs which execute the visible response are motor organs (q.v.). cushions by the leaves of the sensitive plants. The best example of this is found in the :Nlinnosa of grpenlionses. \Viten this plant is jarred, struck, locally burned, or injured other wise, its leaves suddenly eollapse. even those al a distance from the shock. Its leaves are doubly compound. and in closing the pintudes rise so that the tipper faces of opposite ones are brought together, the pion:' drop downward of tissue tpulvini) situated one at the base of the leaf, of each pinna. and of each pinnule. Indigenous plants which show this reaction, though not so strikingly. are the common oxalis and different species of Cassia.
The 'sleep of leaves of the pea family, Oxalis, etc_ are Cxecutcd by the same motor organs, which, however, are often fectly developed. These movements consist of changes in the position of the leaf variations in the intensity of illumination. so that these leaves have a nocturnal and a diurnal position. Hence the misleading expression 'sleep movements.' For a discussion of the variety of movements of plants in response to stimulation, which are brought about by unequal growth on opposite sides of an organ, see CIIEMOTROPISM ; ELECTROT ROPISM ; GEOTROPISM IN PLANTS; HELIOTRoP I SM ; RH EOTROPISM ; THERMOTROPISM. See, Alvxo