MECHANICAL USES OF WATER. 59 



dril does after the free end has caught hold of some place for 

 support. 



120. Transverse tissue tension. To illustrate this one may 

 take a willow shoot $-$cm in diameter and saw off sections about 

 2cm long. Cut through the bark on one side and peel it off in a* 

 single strip. Now attempt to replace it. The bark will not 

 quite cover the wood again, since the ends will not meet. It 

 must then have been held in transverse tension by the woody 

 part of the shoot. 



