EXERCISE 76 

 HOW DOES A PLANT ABSORB WATER? 



Materials. A short-stemmed thistle tube or a metal cup (known as the Lyon Osmometer), such 

 as is shown on page 235 of " Elements of General Science " ; glass tubing ; rubber tubing ; small 

 cord or copper wire ; some thick sirup, sugar solution, or salt solution ; parchment paper, or animal 

 bladder, or sausage casings. 



Directions. Close the stem of the thistle tube or metal cup and place the cup with the stem 

 downward ; pour the sirup or other thick solution into the cup and fasten the membrane securely 

 over the opening of the cup ; turn the cup with the stem upward and open the stem ; by means of 

 rubber-tubing connections fasten a long glass tube to the stem of the cup ; stand the cup in a dish 

 of pure water and fasten the tube securely ; observe the apparatus at intervals for three or four days 

 and record observations. How are the results of this experiment similar to those of Exercise 75 ? 

 How different ? In what ways does this experiment explain how plants secure their water ? 



Additional problems. Bore a hole in the top of a beet or carrot ; place sugar in the hole until it is 

 almost full ; stopper the hole with, a one-holed rubber stopper, a glass tube having first been inserted ; set 

 the apparatus in a vessel of water ; and support the glass tube in an upright position. Observe as in the 

 above experiment. 



When a strong salt solution, such as that from an ice-cream freezer, is poured upon the lawn, the plants 

 upon which it is poured usually die. Why ? 



What is the explanation of the common practice of putting a handful of salt upon the cut sterns or 

 roots of weeds ? 



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