350 



VEGETABLE PHYSIOLOGY 



filled with granules, as in their absence it is so transparent 

 that it is impossible to say whether it is in motion or not. 

 In the leaf of Elodea we find a very good instance of this 

 movement. Each cell contains a considerable quantity of 

 water, so that the protoplasm for the main part is found as 

 a layer lining the cell-wall. This layer consists of two 

 parts, an outer one in which are situated the chloroplasts, 

 and an inner one in which are large numbers of fine 

 granules. It is this inner layer which exhibits the move- 



FIG. 151. CELLS FBOM THE LEAP 

 OF Elodea. x 300. 



?i, nucleus ; p, protoplasm, in which 

 are embedded numerous chloro- 

 plasts. The arrows show the 

 direction of the movement of the 

 protoplasm. 



FIG. 152. Two CELLS FBOM A 

 STAMINAL HAIK OF Trades- 

 cant ia. x 300. 



The arrows show the direction 

 of the movement of the 

 protoplasm. 



ment, which can be seen as a streaming motion of the 

 granules, the whole layer flowing slowly round the cell 

 (fig. 151). 



In other cases, particularly in long pollen-tubes, where 

 the distribution of the protoplasm is so far different that 

 bands or bridles of it cross the vacuole in various directions, 

 the movement has a more complicated course, streams of 

 granules passing along these bridles as well as along the 

 peripheral portions of the protoplasm. These two cases of 



