332 MOTION IN CHARA. [BOOK n. 



be examined, a current of sap will be distinctly seen in each 

 cellule, setting from joint to joint, flowing down one side and 

 returning up the other, without any membrane intervening to 

 separate the opposing currents ; each cellule has a movement 

 of its own, independent of that of the cellules above and below 

 it ; sometimes the movement stops, and then goes on again 

 after a brief interval ; if a cellule is divided into two by a 

 ligature passed round it, a separate movement is seen in each 

 of the divisions; this motion is rendered distinctly obvious 

 by the numerous minute green granules which float in the 

 transparent fluid, and which follow the course of the currents. 

 The observations of Amici have been verified and much 

 extended by subsequent investigations. 



Among other things, it has been ascertained that in Nitella 

 the currents have always a certain relation to the axis of 

 growth, tha ascending current uniformly passing along the 

 side of the cell most remote from the axis, and the descending 

 current along the side next the axis. 



Mr. Varley considers (Trans. Soc. Arts, xlix. p. 20.) that, 

 in addition to the principal current, which he finds setting 

 up one side and down the other within the green interior 

 granular sac of each joint of Chara, there are two others, of 

 which one takes place between the side of the interior sac 

 and the side of the outer transparent coating, the other 

 current is said to occur in the centre of the interior cell, and 

 to be very sluggish. 



A further and very detailed examination of the Chara 

 fragilis has been made by M. Dutrochet, the general results 

 of which are to be found in the Ann. des Sciences, n. s., vol. ix. 

 p. 73. It appears from them, among other things, that ex- 

 periments, expressly instituted by M. Becquerel, show the 

 motion not to be owing to a voltaic action of the green globules 

 lining the cells, nor to any known form of electrical agency, 

 but to vital force ; and, also, that the rapidity of the movement 

 is increased by an elevated, and diminished by a lowered, 

 temperature, the mean rate of motion of the swimming 

 granules being a millimetre (-&& f a li ne ) i Q 35 or 36 

 seconds. 



Similar motions have been seen in several other plants. 



