430 
Cotton  Root  Bark. 
/Am.  Jour.  Pharm. 
\  September,  1898. 
broken  and  eroded  on  the  outer  surface,  and  containing  in  the  outer 
layer  tannin  and  coloring  matter.  Underneath  this  corky  layer  lies 
a  parenchymatous  tissue  (/)  consisting  of  a  number  of  layers  of 
thin-walled  cells.  Into  this  latter  extends  a  wedge-shaped  mass  of 
bast  fibres  (b).  The  latter  is  arranged  in  layers,  separated  from  one 
another  by  layers  of  parenchyma  (p)  and  sieve  cells  (5),  the  lower 
layers  being  very  much  broken  by  short  medullary  rays  {m'y  There 
also  occur  secretion  reservoirs  (s)>  and  cells  containing  starch,  tannin 
and  oxalate  of  calcium  crystals.  The  latter  are  rosette-shaped  and 
relatively  numerous  in  the  inner  bark.  Frequently  the  secretion 
reservoirs  can  be  seen  by  the  naked  eye,  especially  if  the  soft  mate- 
rial is  freshly  sectioned. 
In  making  a  micro-chemical  examination  of  the  bark  for  tannin, 
some  of  it  was  macerated  for  two  weeks  in  an  aqueous  solution  of 
copper  acetate  (method  employed  and  suggested  by  Professor 
Kraemer),  which  has  the  effect  of  precipitating  tannin  as  reddish 
masses  in  the  cells  containing  it.  On  sectioning  and  examining 
with  a  magnification  of  twenty  five  diameters,  tannin  was  identified  in 
the  outer  row  of  cork  cells,  but  it  occurs  most  abundantly,  however, 
in  the  first  layers  of  parenchyma  just  beneath  this  cork  layer.  This 
tannin-containing  parenchyma  tissue  is  from  one  to  five  cells  in 
width.  Tannin  also  occurs  in  isolated  parenchyma  ceils  throughout 
the  bark,  especially  lying  between  the  wedge-shaped  groups  of  bast 
fibres  and  in  the  cells  lying  adjacent  to  the  groups  of  bast.  Of  the 
latter,  generally  only  those  cells  contain  tannin  which  are  arranged 
on  the  outer  and  inner  tangential  surfaces  of  the  bast  bundles. 
It  is  also  found  in  the  secondary  medullary  ray  cells. 
Calcium  oxalate  crystals  are  found  occurring  frequently  in  the 
primary  medullary  rays,  and  in  the  cells  lying  on  either  side  of  the 
cells  of  the  smaller  rays  ;  occasionally  in  the  parenchymatous  tissue 
of  the  outer  bark. 
Secretion  reservoirs  (Y),  containing  oil  and  resin,  occur  frequently  in 
among  the  parenchymatous  tissue  lying  near  the  phloem.  These 
are  large  enough  to  be  distinguished  (in  fresh  bark)  by  the  naked 
eye.  The  reservoirs  are  apparently  of  lysigenous  origin.  The 
contents  were  found  to  be  soluble  (on  maceration) ;  in  acetone  and 
alcohol  very  soluble  ;  in  chloroform  and  dilute  alcohol  slightly  solu- 
ble ;  insoluble  in  water.    The  bark,  macerated  in  alcohol  and  ace- 
