STEMS 97 



and dead tissues are disposed with regard to each 

 other. 



127. Methods hy ivhich firmness is secured. — If 

 the stem is to hold the leaves and flowers aloft, 

 it must secure a certain amount of rigidity in its 

 own body. It does this by two methods, which 

 may be illustrated as follows : Cut off a fresh branch 

 from a woody tree, and also the stem of a tomato or 

 potato, ajad lay in the hot sun for two hours. Take 

 a second fresh branch from the tree and bend or 

 break it across the knee. Bend or break the one 

 which has lain in the sun in the same manner. Has 

 the latter lost any of its rigidity or firmness ? Is it 

 more easily bent ? Repeat with other stems. What 

 is the result ? It will doubtless be found that the 

 herbaceous stem has lost its firmness and that it is 

 wilted and may be very easily bent double, while the 

 ivoody stem is practically unchanged. Both stems 

 lost water in the sun. This did not affect the woody 

 stem, but did the other. It seems fair to conclude 

 that the presence of water is necessary for the firm- 

 ness of herbaceous stems, and it is not for the woody 

 stems. If the experiment is carried farther, it will 

 be found that dead and thoroughly dried stems 



