358  Structure  of  Our  Hemlock  Barks.  {Am'^;^rm' 
in  medicine  for  the  same  purpose  as  Burgundy  pitch.  Tsuga  Mer- 
tensiana  occurs  on  the  Pacific  Coast  from  the  vicinity  of  San  Fran- 
cisco northward  to  Alaska.  While  very  similar  in  appearance  to 
our  Eastern  species,  it  is,  when  fully  developed,  a  tree  of  much 
larger  size,  sometimes  attaining  a  height  of  200  feet.  It  is  also 
straighter-grained,  and  has  a  redder  and  usually  thicker  bark ;  but 
the  most  distinctive  difference,  perhaps,  is  in  the  fruits  and  seeds, 
the  scales  of  the  cones  being  more  elongated  and  the  wings  of  the 
$ 
Fig.  2. 
seeds  being  relatively  longer  and  straighter.  The  wood  and  bark, 
like  those  of  our  Eastern  species,  are  used  for  lumber  and  tanning 
purposes,  respectively,  but  whether  or  not  any  commercial  use  is 
made  of  the  pitch  certainly  obtainable  from  the  bark,  the  writer  is 
not  informed. 
The  barks  of  these  two  species  are  the  only  ones  the  writer  has 
examined  microscopically.  The  barks  show,  as  might  have  been 
expected,  a  great  similarity  in  structure,  though  there  appear  to  be 
