THE STEM 



41 



2. You see, then, that just as the hard bones 

 support the body of a man, so the heartwood supports 

 the tree; and just as the veins carry the blood 

 through the human body, so the sap-tubes carry the 

 sap to all parts of the tree. And you must notice that 

 the sap-tubes have very tough sides and so are able 

 not only to carry sap to and from the leaves, but to 

 support the stem and the leaves The tubes that run 

 into a leaf are thus able to act as bones as well as 

 veins. And now we shall make 



3. Experiments to shew the water-path in stem 

 and leaf. Cut a vine-shoot which ends in a leaf, and 

 place the cut end in a vessel containing red ink. In 

 a short time, you will see the red ink colouring the 

 smallest veins. Then cut through the shoot with a 

 sloping cut, and you will see a ring of small, red, 

 round spots, shewing the tubes up which the ink has 

 flowed. This ring of red spots is between the bark 



and the pith. Since 

 neither pith nor bark 

 are red, we know that 

 the ink has not run up 

 the bark nor the pith.* 

 Then split the shoot, 

 and you will see the long 

 red streaks that shew 

 where the ink has run. 

 These red streaks are the 

 tough tubes that run up 

 through the sap-wood 

 from the smallest root- 

 hairs to the smallest 



Grape vine shoot, Tiering of dots 



between pith and bark shows the 



root-sap tubes. 



* Besides this quick movement up the sap-wood tubes there is a slower 

 -movement which, in time, stains the whole of the wood. 



