PROTOPLASM AND ITS PROPERTIES 185 



195. Circulation of Protoplasm. — When confined by a 

 cell-wall, protoplasm often manifests a beautiful and con- 

 stant rotating movement, traveling incessantly up one 

 side of the cell and down the other.^ A more complicated 

 motion is the circulation of protoplasm, shown in cells of 

 the jointed blue hairs in the flower of the common spider- 

 wort and in the stinging hairs of the nettle (Fig. 127). 

 The thin cell- wall of each hair is lined with a protoplasmic 

 layer in which are seen many irregular, thread-like cur- 

 rents, marked by the movements of the granules, of which 

 the protoplasmic layer is full. 



1 See Huxley and Martin's Elementary Biology, under Chora. 



