THE FOOD OF THE PLANT 15 



It was observed also that the water in the basin 

 became sweet, therefore some of the syrup from the 

 bulb of the funnel must have passed out into the water. 

 This interchange of liquids is termed Osmosis. 



The above experiment illustrates very roughly the 

 method of absorption in the root of a plant. The syrup 

 is analogous to the cell-sap, the membrane represents 

 the wall of a cell of the root, the beaker of water takes 

 the place of the water in the soil. Further, the passage 

 of some of the sugar solution out into the water is 

 analogous to the outflow of acid proved in Experi- 

 ment 5. 



A further experiment will determine whether sugar 

 exerts a similar attraction when acting through the 

 tissues of a plant instead of through pig's bladder. 



Experiment 7 



Aim. — To find out whether sugar possesses the power 

 of attracting water through the cells of a plant. 



Method. — For this experiment three large potatoes 

 are used. Young ones are the best to work with, and 

 they should have sound skins. From the end of each 

 a sufficiently large piece is cut to enable the potato to 

 stand steadily. At the other end a pit is made. This 

 is best done with a cork-borer. Each pit should have 

 a diameter of about half an inch and a depth of one 

 inch. A width of about half an inch at the cut end of 

 the potatoes is carefully peeled, and they are then 

 placed in separate glass crystallizing-dishes. 



A little crystallized sugar is put into two of the pits, 

 and a few drops of water, just enough to moisten the 

 sugar, are added. The pit in the third potato is left 

 empty. Water is poured into two of the glass dishes, 

 those which hold respectively the potato with the 

 empty pit and one of the potatoes with sugar in 

 the boring. Thus the second potato which has had 



