PRACTICAL EXERCISES 33 



diffuses out of the cells : hence it is evident that though 

 the colouring-matter does not diffuse out of a living 

 cell, it diffuses readily out of a dead cell. 



b. Mount another section in water, and run some 

 2^ per cent, salt solution under the cover-slip; it will 

 be seen that the red sap collects as rounded deeply- 

 coloured bodies in the centre of the cells. This is due, 

 as in the previous cases, to the contraction of the 

 primordial utricle. Wash out the salt solution with 

 water, and some at least of the plasmolyzed cells will 

 gradually reassume their original appearance. 



V. In order to observe the movements of proto- 

 plasm in the living cell, mount in water a rootlet 

 of Trianea Bogotensis, or, if that be not available, of 

 Hydrocliaris morsus-rance : examine it first with a low 

 power, and note the solid cylindrical body of the root 

 with its conical apex : its surface is studded, except 

 near to the apex, by transparent cylindrical out-growths 

 the root-hairs. Neglecting the body of the root, 

 focus under the high power upon one of these hairs, 

 and observe : 



1. The thin, smooth cell-wall. 



2. The granular protoplasm constituting the prim- 

 ordial utricle which lines it, and surrounds the large 

 central vacuole, from which it is separated by an 

 irregular inner surface. 



o 



Focussing carefully upon the granules in the proto- 

 plasm, these may be seen to be in motion, being carried 

 along by a streaming movement of the protoplasm 

 (rotation). By gently warming the slide on the palm 

 of the hand, or over a lamp, the movement may be 

 accelerated. 



D 



