ON  AFRICAN  TRAGACANTH. 
439 
If  this  shall  succeed  in  leading  any  to  a  closer  study  of  nature's 
beauty,  and  the  goodness  and  glory  of  the  Creator,  its  object 
will  be  answered. — The  Am.  Naturalist,  May,  1869. 
ON  AFRICAN  TRAGACANTH. 
By  Dr.  F.  A.  Fluceiger,  of  Bern. 
The  substance  ^to  which  I  here  apply  the  name  of  African 
Tragacanth  is  an  exudation  from  the  trunk  of  Sterculia  Traga- 
cantha,  Lindl.,  a  tree  of  moderate  size,  occurring  in  tropical 
Western  Africa  from  Senegambia  to  Congo.  Mucilaginous  mat- 
ter is  known  to  characterize  several  plants  of  the  order  Stercu- 
Uaeece,  in  which  respect  one  of  the  most  noteworthy  is  Sterculia 
urens  Roxb.,  an  East  India  tree  which  exudes  abundantly  a  sub- 
stance resembling  tragacanth.  The  exudation  of  the  African 
species  under  notice  has  also  long  been  known  ;  but  as  its  chemi- 
cal nature  has  not  hitherto  been  investigated,  I  think  the  follow- 
ing observations  may  be  of  interest.  The  specimen  examined  is 
authentic,  having  been  collected  with  the  plant  by  the  late  Mr. 
Barter,  and  transmitted  to  the  Royal  Gardens  of  Kew. 
African  Tragacanth,  as  I  have  received  it,  consists  of  irregular, 
knobby,  undulated,  droppy,  or  stalactitic  masses,  more  or  less 
bubbly  or  cavernous,  often  exceeding  an  ounce  in  weight,  of  a 
pale  yellowish  hue  or  almost  colorless,  in  small  fragments  nearly 
transparent,  but  seen  in  mass  somewhat  opaque  by  reason  of  in- 
numerable cracks,  which  also  render  it  much  more  brittle  than 
true  tragacanth.  Each  mass  is  in  fact  traversed  by  curved  fis- 
sures answering  to  successive  protrusions  of  gum.  Fragments 
of  bark  are  often  adherent  to  the  flat  or  inner  side  of  the  pieces. 
With  20  parts  of  water,  coarsely  powdered  African  traga- 
canth forms,  like  common  tragacanth,  a  thick  tasteless  jelly ; 
with  40  parts  of  water,  the  jelly  becomes  more  fluid.  Only  a  very 
small  quantity  of  gum  is  really  dissolved  in  the  water  ;  the  fil- 
tered liquid  is  not  precipitated  either  by  neutral  acetate  of  lead 
or  by  absolute  alcohol,  but  on  addition  of  basic  acetate  of  lead 
it  becomes  a  little  turbid.  The  jelly  itself  reddens  litmus  paper. 
Neither  thin  slices  of  the  dry  tragacanth  nor  the  jelly  exhibit 
any  trace  of  cellular  structure  or  of  startch,  even  when  examined 
