82 GENERAL BOTANY 



cork, in the course of a few years, may become two 

 or three inches thick, or even more, and it can then 

 .be cut off, and made into corks for bottles, etc. 



Just as layers of hard and of softer wood are formed 

 in different seasons of the year, so, too, layers of hard 

 and soft tissue are formed in the cork. These can 

 nearly always be seen in any bottle-cork the softer 

 broader part is formed in the spring months, March, 

 April, May, and the other later on in the year. 



It is the waterproof and yielding, yet firm nature 

 of cork, that renders it so useful for keeping liquids 

 in bottles, etc. ; and it is precisely those same charac- 

 teristics that make it so useful to the tree. For it 

 prevents loss of sap by evaporation from the surface 

 of the tree, and the dead tissue outside offers no 

 attraction to animals to nibble at the trunks. In 

 FICUS (Banyan, Peepul, etc.) and some other trees 

 the cork and bark are very thin and can easily be 

 bitten through ; but the sticky and poisonous milky 

 juice contained in these trees prevents animals to a 

 certain extent from doing much damage. 



Again in many trees a second layer of phellogen 

 is formed deeper in the wood, and by forming cork 

 cuts off the sap from the original phellogen, which 

 therefore dies. When this happens the outer part, 

 from the first layer of phellogen outwards, generally 

 comes off, it may be in flakes as in STEPHIGYNE, 

 PINUS (Pine) and PLATANUS, the Plane-tree, or in long 

 pieces as in the EUCALYPTUS, or in almost complete 

 cylinders as in the Cherry-tree and Birch. 



On the young branches of very many shrubs and 

 trees there are often to be seen little brown or 



