THE EOOT 



21 



of glass tubing, and fit it iato the rubber tubing. Tie 

 tightly, and then, in order to keep the glass-tubing 

 upright, fix it to a stake. The water, in a few hours, 

 ■will rise in the tube and continue to do so for a day 

 or two. The soil must be watered as if the plant were 

 uncut. 



8. How the water passes from the earth into 

 the root. And now I am ready for the question 

 ■which you have been waiting to put : " How is it that 

 ihe water passes from the earth into the root-cell, but 

 cannot pass from the root-cell into the earth ? " To 

 understand this, take a large, long potato, and hollow 



it out carefully, as shewn in the 

 Figure. Place in the bottom of 

 this potato-tube a dessert-spoonful 

 of sugar, and then place the tube in 

 a tumbler that has a little water in 

 it. Mark on the tumbler the level 

 of the water, and note how, in a 

 day or two, this water is drawn into 

 the tube and up the tube. In a few 

 days the water may be at the brim 

 of the potato-tube. And now re- 

 verse the process. Empty the 

 potato-tube and tumbler, and put 

 pure water in the potato, and strong 



isugared water in the tumbler. The water will now 



pass from the potato into the tumbler. 



9. Now, what does all this mean ? It means that 

 the flow of liquid is always from the weaker to the 

 stronger fluid. This is why the water, in both cases, 

 flowed towards the sugared water. Now, the fluid in 



Tube made of a 

 ■potato, to show how 

 roots suck up water. 



