HOW PLANTS DO THEIR WORK 293 



for the second pot. This solution should be renewed at 

 least once a week. 1 



We have now seen that that soil water with raw 

 material goes into the roots. We have also seen that one 

 function of this water is to hold the plant rigid. We are 

 now ready to ask, Where does this water go, and what 

 finally becomes of it? 



Experiment. — Cut off a growing twig from a maple, 

 or box-elder tree; also the stem of a growing bean or sun- 

 flower close to the ground. The plant should be at least 

 five inches high. Place these cut stems in a tumbler half 

 full of water to which you have added a tablespoonful of 

 red ink. Allow these to stand twenty-four hours. With a 

 sharp knife slice off small sections of the stems and ex- 

 amine closely. Through what part of the tree stem did the 

 water travel upward? This is called the wood, the soft 

 portion in the middle is the pith, and the portion outside 

 the woody part is the bark. If you look at this closely 

 you will see that it is made up of three layers — the brown 

 epidermis on the outside, the green layer in the middle, 

 and the white bast on the inside. The sticky layer between 

 the bast and the wood is the cambium. Where did the 

 water travel upward in the sunflower? In the bean? 

 Those spots are made of woody fibers and correspond to 

 the wood in the maple twig. You will remember in the 

 study of germination of seeds that we classified plants into 

 dicots and monocots. Is a bean a dicot or a monocot? 



1 The above experiment may be tried by using food tablets in the 

 water. These tablets contain the same kind of compounds found in the 

 soil. They may be procured at ten cents a box with directions for using 

 from Edward F. Bigelow, Stamford, Conn. 



