^"'j'i^y'^im*'^™"}        Pharmacognosy  of  Echinacea.  317 
DESCRIPTION  OF  RHIZOME  AND  ROOT. 
The  crown  of  the  rhizome  is  simple  or  branched,  resembhng  that 
of  other  Compositse.  The  undergroinid  stem,  or  rhizome,  attains  a 
length  of  as  much  as  12  centimetres,  and  is  from  10  to  15  milli- 
metres in  diameter.  It  is  slightly  annulate,  marked  by  a  number  of 
V-shaped  stem  scars  and  circular  root  scars,  but  otherwise  it  is 
nearly  smooth  and  of  a  somewhat  purplish-brown  color.  The  root 
is  continuous  with  the  rhizome  and  extends  downward,  producing 
a  number  of  irregular  branches. 
The  commercial  drug  may  be  described  as  follows :  Nearly  entire, 
cylindrical,  very  slightly  tapering,  10  to  20  centimetres  long,  4  to 
8  millimetres  in  diameter ;  externally,  grayish  brown,  light  brown  or 
purplish  brown,  slightly  annulate  in  the  upper  portion,  with  occa- 
sional V-shaped  stem  scars,  somewhat  wrinkled  longitudinally,  or 
furrowed  and  sometimes  slightly  spirally  twisted ;  fracture  short, 
fibrous ;  internally,  bark  less  than  i  millimetre  in  thickness,  wood 
thick  and  composed  of  alternate  light  yellowish  and  black  wedges ; 
the  rhizome  with  a  circular  pith ;  odor  faint,  aromatic ;  taste  sweet- 
ish, followed  by  an  acrid  and  tingling  sensation  resembling  that  of 
aconite  but  lacking  the  persistency  and  numbing  qualities  of  the 
latter. 
MICROSCOPICAL  STRUCTURE. 
The  outer  portion  of  the  rhizome  and  root  (Fig.  i)  consists  of 
two  to  four  layers  of  more  or  less  tabular  cork  cells  with  somewhat 
thickened  yellowish  suberized  walls,  the  cells  being  frequently  filled 
with  more  or  less  spherical  globules  of  a  substance  which  may 
become  changed  to  a  granular  form.  Beneath  these  outer  layers 
of  cork  occur  six  to  eight  rows  of  tangentially  elongated  cells  with 
more  or  less  thickened  walls,  which  are  usually  rich  in  cytoplasm, 
and  in  which  is  frequently  found  a  distinct  nucleus.  In  among 
these  cells  also  occur  some  intercellular  (schizogenous)  oil  and 
resin  cavities  or  reservoirs  (Figs,  i,  4  and  5).  Beneath  this  second 
layer  occur  from  twelve  to  twenty  rows  of  parenchyma  cells  of  vary- 
ing shape,  among  which  are  large  intercellular  oil  reservoirs  and 
numerous  small  stone  cells  (Figs,  i,  2  and  3).  These  stone  cells 
are  usually  more  or  less  elongated,  and  frequently  ten  to  twenty 
times  as  long  as  they  are  wide.  They  are  of  considerable  interest 
by  reason  of  the  fact  that  in  the  intercellular  spaces  and  in  some 
of  the  adjoining  cells,  occur  blackish,  carbon-like,  resinous  masses 
