392 Field, Forest, and Wayside Flowers 



lies just behind the root-tip, ready to put out fresh 

 root-hairs as soon as spring returns. 



While the root-tips are being enclosed in cork- 

 sheaths, preparations for a long winter sleep are 

 going forward among the branches overhead. 



All the trees which wear union suits of cork have 

 on their youngest branches little ventilating holes, 

 called " lenticels. " These can be plainly seen on 

 the twigs of birch, beech, cherry, and elder, as 

 rough oval dots, slightly raised, and different in 

 color from the bark around them (Fig. 102). 



Those of the birch become greatly extended as 

 time goes on and appear as sharply-drawn, blackish 

 stripes, running horizontally around the trunk. But 

 on the roughened older bark of most species of 

 tree the lenticels are hard to find, though they are 

 still there. 



In the older bark of the cork-oak, however, we 

 know them only too well, for the brown, powdery 

 streaks which sometimes run through bottle-corks, 

 and cause them to crumble vexatiously when one 

 tries to draw them, were the lenticels of the growing 

 tree. 



A lenticel is a lens-shaped rift in the outer bark, 

 filled in with a loose mass of cork-cells, which are 

 not rectangular, and ranged in rows after the 



