Am.  Jour.  Pharm.  \ 
December,  1896.  J 
North  American  Conifer  ce. 
647 
cluster  from  three  to  about  seven  cells  long.  The  cells  of  the 
medullary  rays  were  observed  also  to  contain  much  starch. 
The  leaves  of  this  hemlock  are,  when  young,  of  a  fine  light  green 
color,  which,  at  maturity,  changes  into  a  deep  but  still  vivid  green. 
In  form  they  are  linear,  from  one-half  to  three-fourths  of  an  inch 
long,  and  about  one-sixteenth  to  one-twelfth  of  an  inch  wide,  obtuse 
at  the  apex,  contracted  below  into  short  green  petioles  about  one- 
twenty-fifth  of  an  inch  in  length  ;  these  readily  break  away,  on  dry- 
ing, from  the  elevations  on  the  stem  on  which  they  are  inserted  ; 
Fig.  5<5. — Cross-section  of  leaf  of  Tsuga  Canadensis,  magnified  about  65 
diameters.  A,  large  epidermal  cell  at  margin  of  leaf ;  b,  thick-walled  epider- 
mis of  under  surface  ;  st,  one  of  the  stomata  ;  sec.  r.,  secretion  reservoir  be- 
tween m^d-rib  and  lower  epidermis  ;  en,  endodermis  ;  xy,  xylem. 
the  margins  of  the  blade  are  roughened  by  sharp,  anteriorly 
inclined,  rather  distant  teeth.  The  upper  surface  is  smooth  and 
deep  green,  while  the  lower  surface  is  glaucous-white  on  each  side 
of  the  mid-rib.  These  glaucous  areas  indicate  the  position  of  the 
crowded  stomata  arranged  in  longitudinal  lines,  about  six  lines  on 
each  side  of  the  mid-rib.  The  rows,  however,  are  commonly  more 
or  less  interrupted.  A  considerable  area  of  the  under  surface 
adjacent  to  the  margin  is  free  from  stomata,  as  well  as  the  whole  of 
the  upper  surface. 
