34 PRACTICAL BOTANY 



Heat the slide over a spirit-lamp to boiling-point : 

 the movements will, on examination, be seen to have 

 stopped, the cell having been killed by the high 

 temperature. 



Treat another preparation, in which active movement 

 is going on, with iodine solution : the movement will be 

 arrested, the cell being killed : the protoplasm will be 

 stained brown. 



Similar movements of rotation are to be seen more 

 or less clearly in living cells generally, and are easily 

 observed in cells of the leaf of Vallisneria spiralis, 

 Elodea canadensis, and especially well in the large 

 internodal cells of Nitella, &c. 



More complicated movements are to be seen in 

 various hairs, and notably in those which cover the 

 base of the stamens in species of Tradescantia. 



Remove a few of the hairs from a stamen of an open 

 flower, and mount them in water. Observe under a 

 low power the moniliform hairs, each composed of a 

 row of barrel-shaped cells. Focus the high power upon 

 one of these cells, and note the limiting cell-wall, and 

 protoplasmic lining : threads or bridles of protoplasm, 

 irregularly disposed, pass from the peripheral protoplasm 

 towards the centrally disposed, spherical nucleus. 



Examination of these threads will disclose movements 

 of the protoplasm in various directions : these more com- 

 plicated movements are collectively termed circulation. 

 The hairs should be treated as above directed in the 

 case of the root-hairs, to show that the movement 

 depends upon the life of the cell. 



