506 
BARK  OF  CEDRELA  FEBRIFUGA. 
appears  to  be  composed  of  several  alternating  layers  of  cork  and 
parenchyma  cells,  and  is  therefore  a  true  rhjtidoma.  The  last 
mentioned  cells  are  filled  with  brown  coloring  matter  ;  they  are 
more  roundish  in  the  secondary  parenchyma,  thin-walled,  inter- 
mixed with  many  small  groups  of  bast  cells. 
The  innermost  corky  layer  is  followed  by  a  few  thick- walled 
porous  cells,  filled  with  a  brown  resin  or  coloring  matterj  and 
by  the  inner  parenchyma  ;  consisting  of  uniform  somewhat 
tangentially  elongated  cells,  which  are  likewise  filled  with  brown 
coloring  matter.  The  outer  layer  of  this  portion  contains  but 
few  bast  cells ;  in  the  inner  layer,  however,  rows  of  such  cells 
alternate  with  parenchymatous  strata.  These  several  layers 
are  separated  by  dark  brown  lines,  probably  intercellular  mat- 
ter, which  are  produced  by  the  one-sided  thickening  of  the  walls 
of  a  whole  row  of  parenchyma  cells.  The  contexture  is  again 
radially  divided  by  numerous  light  large-celled  medullary  rays, 
so  that  the  whole  inner  bark  appears  to  be  divided  into  rectan- 
gular fields,  which  are  tangentially  elongated,  and  may  be  re- 
cognized by  the  magnifying  glass. 
The  bark  is  free  from  starch,  but  it  is  interspersed  with 
numerous  rosettes  of  crystals  of  oxalate  of  lime,  precisely  like 
the  roots  of  rheum,  viola,  fragaria,  vincetoxicum,  cortex  canellse 
albse  and  many  other  drugs. 
The  longitudinal  tangential  section  shows  the  very  long  bast 
cells,  the  apparently  elongated  parenchyma  cells,  and  the  crys- 
tals in  rows  in  the  interstices. 
The  whole  anatomical  structure  of  Cedrela  bark  reminds  of 
cinchona,  and  approaches  Loxa  bark  probably  nearer  than  any 
other,  though  they  may  be  readily  distinguished  by  external 
signs.    The  difference  in  their  anatomy  is  as  follows : 
Cedrela  bark  wants  a  resin  ring,  observable  with  the  naked 
eye,  though  resin  cells  are  present ;  starch  is  likewise  wanting. 
Instead  of  the  crystal  cells  of  the  cinchona  barks,  containing 
single  crystals,  Cedrela  bark  has  them  always  in  cavities.  The 
bast  cells  resemble  those  of  the  cinchonas  very  much,  but  are 
invariably  much  thinner,  longer,  less  plainly  arranged  in  layers 
and  rarely  with  porous  canals.  The  cross-section  shows  the  bast 
cells  roundish,  not  angular  like  those  of  cinchona,  and  either 
with  very  little  lumen  or  entirely  closed.    While  their  diameter 
