DIFFUSION AND OSMOSIS 35 



Then fill the large cavity with sugar and cork the top 

 hole tightly. 



Stand the potato in a dish and pour in water up to the 

 height of the peeled area. Let it stand for two or three hours. 

 What is the result? The height to which the liquid rises 

 will measure the osmotic pressure. 



Conclusion. State how osmotic pressure may be meas- 

 ured. 



22. OSMOSIS 



Object. To show that osmosis may take place through 

 the skin of a leaf. 



Apparatus. A bell jar, a plate, a thick leaf of such a plant as 

 the begonia, and a piece of paper. 



Method. Lay the leaf upon the plate and beside it 

 place a piece of paper about the same size. Upon the leaf 

 place a little pile of powdered sugar and put a similar amount 

 upon the paper. Cover the plate with the bell jar and let 

 it stand for several days, looking at it from time to time. 



What happens to the sugar on the leaf? What happens 

 to that upon the paper? Explain the difference. In view 

 of what has been learned from the preceding experiments, 

 how do you account for this ? 



Suggestion. (a) Cut sections of beet root and place 

 them in cold water. 



(6) Boil sections of beet root and then place them in cold 

 water. 



What is the difference in the results ? 



(c) Immerse sections of beet root in wood alcohol, then 

 remove them and place them in cold water. 



How do you account for these results ? 



