PROTOPLASM AND PLANT-CELLS. 19 



bibing water with great avidity withdraws the water of the cell-sap 

 from the cells, causing them to collapse. 



(c) The presence of sugar may be demonstrated in many cases by 

 taste alone, as in the stems of cane and Indian corn. 



(d) Cane-sugar when abundant may be crystallized out (in small 

 stellate crystals) from cell-sap by the use of strong alcohol or glyce- 

 rine. 



(e) Make thin slices of the root of the sunflower or dahlia, and soak 

 for some days in alcohol : the inulin will appear in the shape of 

 sphere-crystals of greater or less size according as the crystallization 

 has been slower or more rapid. 



(/) The presence of acids in the cell-sap of many plants may be 

 shown by placing a moist cut surface in contact with blue litmus- 

 paper. The latter will be distinctly reddened. On the other hand 

 the presence of alkalies may be shown by using red litmus paper, 

 which is turned blue. 



