^"^'jl^i^U^^'""-}  Histology  of  Araroha.       '  359 
THE  HISTOLOGY  OF  ARAROBA  or  GOA  POWDER.^ 
By  Thomas  Greenish,  F.C.S. 
Within  the  last  few  years  much  interest  has  attached  to  a  drug  im- 
ported from  Brazil,  and  to  which  the  native  name  "Araroba"  is 
applied,  and  sometimes  also  "Goa"  powder,  from  Goa,  a  Portuguese 
possession  of  that  name  on  the  Malabar  Coast,  through  which  it  was 
imported  into  British  India. 
Its  chemistry  has  been  investigated  by  Professor  Attfield  and  subse- 
quently by  Liebermann,  the  botanical  characters  of  the  tree  whence  it 
is  produced  have  been  described  and  illustrated,  and  so  much  of  its 
history  as  has  reached  this  country  can  be  gathered  from  various  papers 
in' the  pharmaceutical  journals  of  the  last  five  years. 
The  object  of  this  paper  is  to  deal  with  the  histology  of  araroba,  a 
substance  at  the  present  time  employed  chiefly,  if  not  exclusively,  for 
the  production  of  chrysophanic  acid. 
As  met  with  in  commerce  araroba  is  in  the  form  of  a  powder  more 
or  less  agglomerated  ;  mixed  with  it,  and  covered  by  it,  are  splinters  of 
the  wood  in  which  this  substance  originates.  The  powder  has  an 
intensely  bitter  taste,  and  somewhat  of  a  resinous  adhesion  to  the 
fingers;  it  is  said  that  the  color  is  originally  of  a  fine  yellow,  resemb- 
ling sulphur,  and  that  this  by  exposure  gradually  changes  to  a  rhubarb 
color,  and  then  darkens  to  that  of  aloes.  Occasionally  in  the  com- 
mercial powder  lumps  are  met  with,  which,  when  broken,  show  inter- 
nally a  canary  color,  whilst  the  external  parts  are  dark  brown.  A 
sample  dried  at  100  to  iio°C.  lost  1*98  per  cent. 
The  drawing  No.  i  represents  a  segment  of  a  transverse  section  of 
the  wood  yielding  araroba,  from  an  authentic  specimen  deposited  in 
the  Society's  Museum,  and  the  fragments  of  wood  found  in  the  powder, 
from  sections  of  which  the  other  drawings  were  made,  correspond 
with  this  in  structure. 
The  bark  externally  is  more  or  less  covered  with  lichen,  which  gives 
it  a  somewhat  grey  and  black  patchy  appearance.  The  epidermal  tis- 
sue is  for  the  most  part  thrown  off  by  a  suberous  layer  composed  of  a 
large  number  of  cork  cells  compressed  together  and  forming  a  layer  of 
dense  tissue  ;  within  this  is  a  cellular  tissue  containing  starch  grains, 
and  amongst  these  cells  are  sprinkled  sclerogen  or  stone  cells — cells 
much  thickened  by  secondary  deposit,  and,  therefore,  equally  with  the 
cork  cells,  capable  of  great  resistance  to  external  or  internal  destruc- 
^  Read  at  the  evening  meeting  of  the  Pharmaceutical  Society,  April  7,  1880. 
