EXERCISE 55 



We saw that through the actions of the roots water is made to rise above the surface 

 of the ground (Exercise 44). 



Problem. Can the transpiration from the leaves raise water in a plant ? 



What to use. Glass tube; water; sealing wax or paraffin; a living leaf; small dish 

 of mercury. 1 



What to do. Fasten the stalk of a vigorous leaf in the end of a glass tube with sealing 

 wax or paraffin. 



Fill the tube with water and place the open end in the mercury, avoiding the entrance 

 of air bubbles. 



Watch the set-up from time to time for any change in the level of mercury in the tube. 



CAUTION. See that the end of the stalk is clean and free from the sealing material. 



Record. Tell what happens and show what light it throws on the problem of the rise 

 of water to the top of a high tree. 



Questions. 1. Under what conditions would leaves give off the largest amount 

 of water ? 



2. Find out the specific gravity of mercury and calculate the amount of water- 

 raising represented by the change in the column of mercury. 



1 If mercury is not to be had, connect the apparatus as shown in the figure. Any water-raising 

 effect resulting from the transpiration would be shown by the rise of water in the second bottle. 



[60] 



