1 82 FLOWER-LAND. 



ness, as in certain kinds of foreign oak, and is 

 very useful when made into bungs and corks, and for 

 many other purposes. But you can tell me now 

 why the outside of the bark is so dry and dead. Yes, it 

 is because the cork cells hinder the passage of the sap, 

 and both the cork and any other tissues that may be 

 outside it become the dry, hard, outside of the bark, 

 or cortex. 



Now turn to Fig. 1 56, and trace . again the wood, 

 cambium, bast (making up inner bark), and outer 

 bark ; and notice how the latter is continued into the 

 dead outside in Fig. 1 60. 



In roots the fibro-vascular bundles are differently 

 arranged ; but this, and other differences of structure 

 between roots and stems, you will search out in 

 time to come. 



