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.1. A more complicated 
motion is the etrculation 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 Chara. 
