ON  THE  FRANKINCENSE  TREE  OF  WESTERN  AFRICA.  341 
may  be  peeled  off  in  smooth  ribbon-like  layers,  which  cannot  be 
effected  in  the  older  specimens. 
The  gum,  when  of  a  natural  exudation,  mostly  appears  in  a 
liquid  state,  of  a  white  or  pale  straw  color,  in  some  seasons  oozing 
so  copiously  from  the  branches,  that  the  ground  and  shrubs  be- 
neath are,  from  successive  excretions,  thickly  covered  with  white 
spots.  This  effusion,  however,  does  not  occur  so  abundantly 
from  the  cortex,  and  when  so  produced,  appear  in  thin  and  shallow 
layers,  that  mark  their  course  by  whitish  streaks,  that  after  their 
exsiccation  on  the  trunk,  present  all  the  aspects  of  a  saline  efflo- 
rescence. The  gum  while  in  this  state  of  fluidity  cannot  be  col- 
lected for  ordinary  use.  The  substance  offered  for  sale  is  widely 
different,  from  the  effect  of  certain  indirect  agencies,  tending  to 
considerably  modify  both  its  qualities  and  secretion. 
The  Frankincense  tree  is  subject  to  the  attack  of  a  certain 
insect,  termed  by  the  natives  Tumbo,  which  deeply  perforates  the 
bark  in  various  directions.  Its  progress  is  attended  by  long  and 
sinuous  passages,  the  woody  debris  from  wrhich  is  ejected  exter- 
nally by  a  circular  orifice  about  an  inch  in  diameter.  In  the 
course  of  a  few  days,  the  gummy  liquid  issues  largely  from  this 
aperture,  blended  with  minute  ligneous  particles,  which  in  their 
transit  through  these  excavations,  acquire  a  ruddy  or  brown  tint, 
by  degrees  accumulating  in  small  masses,  and  falling  to  the 
earth.  In  this  state  they  become  converted  into  dark  brown 
fragments  after  a  short  interval,  and  are  then  gathered  by  the 
negro  women  and  children,  who  resort  to  the  woods  with  the  ex- 
press purpose  of  collecting  them.  Another  mode  of  procuring 
this  gum  consists  in  stripping  the  dead  or  unsound  bark  from  the 
wood,  the  more  decayed  portions  of  which  are  commonly  satu- 
rated by  the  gummy  exudation,  and  are  found  amalgamated  with 
the  woody  fibre  beneath  in  black  crusts. 
Great  uncertainty  prevails  with  reference  to  the  period  at 
which  this  tree  flowers.  Several  colonists  remark  that  they  have 
not  hitherto  been  seen,  and  the  majority  appear  to  be  as  equally 
ignorant  on  the  subject.  I  observed  the  pod,  however,  was  in  a 
green  condition  early  in  March,  from  whence  we  may  infer  that 
the  flowering  probably  commenced  in  December  or  January.  The 
fruit  is  a  coriaceous,  thin,  and  dehiscent  legume,  from  two  to 
two  and-a-half  inches  long,  and  one  to  one-and-a-half  inch?s 
