CIRCULATION IN PLANTS. 



45 



Chara, this space is the whole interval between 

 two adjacent knots or joints. The appearance of 

 this partial circulation, or rotation, as it has been 

 more specifically termed, is beautifully seen in the 



cells of the Caulinia fra- 

 gilis ; and is represented 

 in Fig. 239, where the 

 directions of the streams 

 are indicated by arrows.* 

 In each of the cells, of 

 which the jointed hairs 

 projecting from the cuticle 

 of the calyx of the Trades- 

 cantia virginica are com- 

 posed, a similar appear- 

 ance (as shown in Fig. 

 240) of partial circulations 

 is presented. t Schultz, however, maintains that it 

 is properly an example, not of rotation, but of 

 cyclosis, and that it is merely a branch of the 

 general circulation of the plant, which is performed 

 by a system of vessels communicating extensively 

 with one another.^ 



Some light has of late been thrown on the cause 

 of these motions of rotation in the fluid contents of 

 the cells of cellular plants, by the discovery of 

 Donne. It had already been shown by Amici, 

 that in the Chara fragilis, the currents follow the 

 course of the spiral lines formed by rows of green 



* This phenomenon was first observed by Corti, in 1774. 



t This was first observed by Mr. Robert Brown. Mr. Slack found 

 that the movement took place in channels which were circumscribed 

 by a fine pellucid membrane. 



X Ann. des. Sc. Nat. Bot. serie 2, x, 327. 



I 



