306 NATURE-STUDY 



ducts. Outside of the tubular part of the stem is the bark, 

 not yet hard in young tree shoots and in herbaceous plants. 



In cornstalks, lily stems, palm stems, and grasses, the 

 strands are not thus arranged, but are found distributed 

 throughout the pithy substance of the stem. 



If we cut across a twig of a tree that has become woody, 



FIG. 1 1 1 . Section of Corn Stalk Showing Fibrovascular Bundles. 

 ( Photomicrograph.) 



we shall see that the woody part is distinct from the bark 

 on the outside and a pithy portion at the centre. In the 

 spring the bark can be easily peeled from the wood. This 

 is because there is then a layer of especially thin-walled cells 

 between them which can be easily torn. In making a whistle 

 of willow or basswood, boys beat upon the bark to crush this 

 layer of cells and thus loosen the bark. It is in this layer, 

 called the growing zone, that the new growth in the thick- 



