THE  GUMS  AND  RESINS  OF  COMMERCE. 
79 
forming  more  or  less  rounded  and  variously-colored  masses, 
weighing  each  from  a  few  grains  to  several  ounces.  These  soon 
bleach  and  whiten  upon  exposure  to  the  light  of  the  sun,  finally 
becoming  nearly  colorless,  semi-transparent,  and  often  filled  with 
minute  fissures.  Specimens  collected  from  the  trunks  of  the 
trees,  were  generally  found  to  be  less  pure  and  more  highly 
colored  than  when  obtained  from  the  branches. 
The  gum  may  be  collected  during  the  months  of  July,  August, 
and  September ;  but  the  most  favorable  period  for  that  purpose 
is  in  the  latter  part  of  August,  when  it  may  be  obtained  in  the 
greatest  abundance,  and  with  but  little  trouble.  The  quantity 
yielded  by  each  tree  varies  from  an  ounce  to  three  pounds  ;  but 
incisions  in  the  bark  not  only  greatly  facilitate  the  exudation,  but 
cause  the  tree  to  yield  a  much  greater  amount.  As  it  is,  a  good 
hand  will  probably  be  able  to  collect  from  ten  to  twenty  pounds 
in  a  day.  Were  incisions  resorted  to,  double  the  amount  might 
be  obtained. 
A  simple,  pure  gum,  was  recently  shown  at  Madras,  obtained 
in  Travancore,  from  the  Maearanga  indica,  which  has  been 
used  for  taking  impressions  of  leaves,  coins,  medallions,  &c. 
When  the  gum  is  pure  and  carefully  prepared,  the  transparent 
impressions  are  as  sharp  as  those  of  sulphur,  without  its  brit- 
tleness.  The  exudation  appears  to  be  an  entirely  unknown  pro- 
duction. 
Keekur  gum,  a  variety  of  Arabic,  is  produced  by  Vachillia 
farnesiana.  Acacia  sirissa  in  India  yields  a  large  quantity  of 
a  clear  gum  known  as  Dirisani  gum,  and  closely  resembling 
Keekur  gum.  Booraga,  obtained  from  Bombax  malabricum,  is 
a  pure  gum. 
Tragacanth  is  a  gummy  exudation,  obtained  from  various 
species  of  Astragulm  ;  A.  verus  (Olivier),  Grurnmifera  creticus 
(Lamarck),  which  is  imported  for  medicinal  purposes  from  Smyrna 
and  other  ports  in  the  Levant,  to  the  extent  of  about  five  or  six 
tons  per  annum.  It  is  obtained  principally  from  Northern  Persia, 
Asia  Minor,  and  America.  Hamilton  (Researches  in  Asia 
Minor,  &c.,)  states  that  tragacanth,  which  is  called  by  the  Turks 
"  kittereh,"  is  collected  in  large  quantities  in  the  hills  about 
Buldur,  from  a  low  prickly  plant,  resembling  a  species  of  furze. 
The  white  flaky  gum  is  obtained  by  making  an  incision  in  the 
