Aid.  .lour.  Fhariu.  I 
August,  1896.  J 
North  American  Conifer  ce. 
411 
Bay  region,  about  the  mouth  of  the  Mackenzie  River,  throughout 
Canada,  along  the  eastern  slopes  of  the  Rocky  Mountains,  and  in 
the  northeastern  portion  of  the  United  States.  It  occurs  as  far 
south  as  Pennsylvania  and  Central  Michigan.  It  is  a  moderate-sized 
tree,  attaining  a  height  of  not  more  than  about  70  feet,  and  a 
diameter  of  not  more  than  3  feet.    It  favors  light  and  rocky  soil,  and 
Fig.  40. — Cross- section  from  stem,  several  years  old,  of  Picea  nigra,rmagni- 
fied  75  diameters.  A  and  b,  periderm  layers,  rich  in  tannic  and'  coloring 
matters  ;  c,  tannin  cells  in  cortex  ;  d,  bast  layer  ;  e,  cambium  zonej;  f,  ring  of 
growth  ;  g,  secretion  reservoir  in  xylem. 
hilly  or  mountainous  localities.  It  is  one  of  the  commonest<of  the 
evergreens  of  our  northern  forests. 
This  species  differs  from  P.  alba  in  having  its  branches  pubescent, 
its  leaves  thicker  and  usually  dark  green  or  but  slightly  glaucous, 
and  its  cones  ovate,  and  with  denticulate  scales.  The  trunk  is 
smooth,  straight,  gradually  tapering  from  base  to  apex.  The  bark 
is  smooth  and  the  branches  horizontal. 
