CH. VlJ TURGIDITY. 93 



which every cell is turgid. Thus the flower-stem and leaf- 

 stalk used in the experiments on withering are stable and 

 rigid, because of the turgidity of the cells which make up 

 the central mass of pith. A woody stem is rigid not 

 from turgidity, but because of the rigidity of its lignified 

 cell-walls. 



