MOVEMENTS IN CELLS — ROTATION. 



151 



experiments that the sap raised the mercury upwards of thirty inches. 

 The apparatus used by Hales is similar to that used by Dutrochet, to 

 measure endosmose, as is represented 



at fig. 243, where c is the stem of a i 



vine cut, t is a bent glass tube fitted 

 to the cut extremity of the vine by 

 a copper ring, v, carefully luted and 

 secured by a bit of bladder, m ; n n, 

 represents the level of the mercury 

 in the two branches of the lower 

 curvature, before the experiment, and 

 n' n' the level at the conclusion of it. 

 He calculated that the force of the sap 

 in the vine, in some of his experi- 

 ments, was five times greater than 

 that of the blood in the crural artery 

 of the horse. 



Special Movements of Fluids. 

 — Besides this general circulation of the 

 sap, special movements have been 

 observed in the individual cells of 

 plants, which have been included 

 under the name of Rotation (rota, a 

 wheel) or Gyration (gyrus, a circuit or 

 circle). These motions have been de- 

 tected in the cells of many aquatic 

 plants, especially species of Ohara and 

 Vallisneria, and in the hairs of Trades- 

 cantia. The currents proceed in a 

 more or less spiral direction, and are 

 rendered visible by the granules of 

 chlorophyll which they carry along 

 with them. There exist also other 

 granules in the fluids, whiph are 

 coloured yelloy by iodine, and are 

 probably of a nitrogenous nature. 



The species of Chara (fig. 244) in 

 which rotation has been observed, are 

 aquatic plants growing in stagnant 

 ponds, and composed of a series of cylin- 

 drical cells, placed end to end. Some- 

 Fig. 243. Apparatus of Hales, to show the force of ascent of the sap. c, Stem of a vine 

 cut. ty A glass tube with a double curvature attached to the upper pai-t of the vine-stem, 

 by means of a copper cap, v, which is secured by means of a lute and piece of bladder, m. . 

 n n, Level of the column of mercury in the two portions of the tube at the commencement 

 of the experiment, n W, Level of the mercury at the conclusion of the experiment. 



Fig. 243. 



