556 
North  American  Conifer  ce. 
(  Am.  Jour.  Pharrn. 
\     October,  ]896. 
for  the  most  part  in  tangential  rows,  but  some  occurred  in  the 
medullary  rays,  and  hence  were  in  radial  rows.  The  xylem  was 
without  secretion  reservoirs,  and  the  tannin  cells,  as  in  the  genus 
Pinus,  were  chiefly  confined  to  the  medullary  rays  and  pith. 
An  examination  of  a  stem  several  years  old  showed,  besides  a 
greater  formation  of  cork,  numerous  scattered  clusters  of  stone 
cells,  some  of  them  branching  and  with  the  branches  often  consid- 
erably elongated.  They  occurred  in  the  outer  portion  of  the  bast 
layer.  Possibly  the  more  fibrous,  branching  forms  are  to  be  regarded 
as  imperfectly  developed  bast  fibres,  forecasting  the  bast  fibres  that 
occur  in  Larix. 
The  leaves  are  linear,  sessile,  yz  to  ^  inch  long,  and  about  y1^ 
inch  in  width,  smooth,  dark  green  and  depressed  along  the  mid-rib 
Fig.  47. — Cross-section  of  leaf  of  Abies  balsamea,  magnified  75  diameters. 
a,  epidermis  ;  b,  b> ',  stomata  ;  c,  Irypoderma  ;  d,  resin  passage  ;  e,  one  of  the  two 
small  fibro-vascular  bundles  ;  f,  endodermis. 
above,  silvery-white  on  each  side  of  the  prominent  mid-rib  below, 
and  usually  slightly  notched  at  the  apex.  A  few  stomata  occur  on 
each  side  of  the  mid-rib  on  the  upper  surface,  but  they  are  much 
more  numerous  in  the  silvery- colored  areas  on  the  lower  surface. 
An  examination  under  the  microscope  showed  the  epidermis  to  be 
composed  of  small,  rather  thick-walled  cells.  There  was  no  hypo- 
derma  observed  except  along  the  mid-rib  on  the  lower  surface.  The 
leaf  contained  two  resin-passages  of  large  size,  with  the  walls  of  its 
strengthening  cells  but  slightly  thickened.  These  passages  were 
buried  in  the  mesophyll,  a  little  nearer  the  margin  than  the  mid-rib. 
The  mid-rib  was  composed  of  two  divergent  collateral  bundles,  of 
