THE WALLFLOWER 43 



embedded (see Fig. 19). The nucleus is very trans- 

 parent, and hard to see. (It is shown dark in Fig. 19.) 

 The protoplasm flows in a continuous stream round 

 and round the cell, carrying the chlorophyll granules 

 with it. Owing to the presence of these granules, the 

 movement is very easy to follow. If we fix our eye 

 on one of the granules which is being swept along by 

 the protoplasmic stream, we shall see it travel steadily 

 along one of the side-walls until it reaches a corner of 

 the cell. Here there may be a momentary hesitation, 

 for at these points the current is often choked by 

 the accumulation of chlorophyll granules. Soon, 

 however, the movement goes on again ; the granule is 

 carried along the short end-wall of the cell, the next 

 corner is reached and turned, and the journey con- 

 tinued along the other side-wall, and so on until the 

 circuit is complete. The revolving protoplasm here 

 forms one single stream, which flows round the whole 

 cell. The current, as we have seen, follows the lateral 

 and terminal walls of the cell. What, then, is the 

 behaviour of that part of the protoplasm which is in 

 contact with the other two walls, those, namely, which 

 form as it were the roof and floor of the cell ? This 

 protoplasm also takes part in the general movement 

 of rotation, and revolves in the same direction as the 

 rest. But it has a shorter distance to cover, and the 

 nearer we approach to the middle of the top and 

 bottom walls, the shorter is the circuit, and con- 

 sequently the slower is the speed. Now, just in the 

 middle of each of these two walls there is a band of 

 protoplasm which does not move at all, but forms a 



