86 



NUTRITION. 



Fig. 52. 



separate division called Characese, and are found in our 

 own country in ponds, and sluggish streams of water; they 

 consist of simple tubes or cells placed one above the other, 

 but having no communication from cell to cell, the mem- 

 brane composing which is more or less transparent, but 

 in some cases covered with a layer of carbonate of lime. 

 65. When a portion of a transparent Chara is exa- 

 mined with the microscope, an incessant movement of 

 little globules is seen along 

 the side of each cell, turn- 

 ing round at the top and run- 

 ning down the other side, then 

 turning round at the bottom, 

 and so repeating a continuous 

 motion along the inner surface 

 of each cell. The relative po- 

 sition and connection of these 

 globules one with another, show 

 that they are quite passive 

 themselves, but are swimming 

 in a fluid which is moving them 

 along : now to this motion the 

 term rotation is applied. 



66. The direction of the 

 streams of rotation in the cells, 

 depends upon the following cir- 

 cumstance : Within the cell, upon its inner surface, 

 are placed a number of green- coloured little bodies, ar- 

 ranged as at fig. 52. In the youngest cells of the plant 

 they are seated parallel to the longitudinal axis of the 

 cell (as at a), whilst in the old ones they are in a spiral 

 arrangement around it (b) ; the space which is left be- 

 tween the series of green bodies being termed by Du 

 Trochet line of repose. 



67. However these bodies may be placed, the streams 

 of rotation always follow their direction, and no motion 

 is to be observed except over where they are situated. 



68. These currents take place in each cell, which is 

 perfectly close, and no connection exists with the cur- 



