FORMATION  OP  GUM  TRAGACANTH. 
161 
INQUIRIES  INTO  THE  FORMATION  OF  GUM  TRAGACANTH. 
By  Hugo  yon  Mohl. 
(Translated  from  the  Botanische  Zeiiung,  Jahrg.  XIY.,  p.  33,  1857.  by  Berthold 
Seemann,  Ph.  D.,  F.  L.  S.,  with  corrections  by  the  Author.) 
An  inquiry  into  the  nature  of  gum  tragacanth  is  not  without 
theoretical  interest,  as  it  is  connected  with  some  difficult  points 
of  anatomy  and  physiology,  which  have  not  yet  been  sufficiently 
explained. 
Tournefort  (Relation  d'un  Voyage  du  Levant,  Amsterd. 
1718,  I.  22,)  was  the  first  to  whom  we  are  indebted  for  closer 
observations  on  the  exudation  of  gum  tragacanth.  His  obser- 
vations were  made  on  Mount  Ida,  in  Crete,  and  on  Astragalus 
oreticus,  Lam.*  Judging  from  a  figure  given  by  him  (p.  21,) 
the  stem  of  the  plant  in  question  attains  about  one  inch  in  thick- 
ness. The  secretion  of  tragacanth  in  the  form  of  twisted  fila- 
ments takes  place  in  June  and  the  succeeding  months.  Tour- 
nefort looks  upon  the  gum  as  the  nutritious  sap  which  has  be- 
come thickened  by  heat,  has  burst  the  vessels,  discharged  itself 
in  the  middle  (dans  le  coeur)  of  the  stem,  and  branches  as  well  as 
in  the  medullary  rays  (dans  T interstice  des  fibres,  les  quelles  sont 
disposees  en  rayon,)  and  is  then  gradually  forced  out  on  the  sur- 
face of  the  stem,  by  the  sap  ascending  by  the  roots,  and  hard- 
ens in  the  air  in  the  form  of  worms.  He  further  adds  the  sup- 
position that  the  contraction  of  the  fibres  of  the  stem  assists  the 
forcing  out  of  the  gum,  as  the  hemp-like  divided  fibres,  exposed 
to  the  tread  of  shepherds  and  horses,  draw  together  in  the  heat, 
and  favor  the  excretion  of  the  sap.f 
*  Sieber  (Reise  nach  Creta,  ii.5  p.  68)  has,  it  is  true,  endeavored  to  show  Tour- 
nefort's statement  to  be  utterly  undeserving  of  credit,  as,  according  to  his  own 
(Sieber's)  observations,  the  plant  named  does  not  yield  any  gum  tragacanth 
whatever  ;  but,  as  not  only  Tournefort's  statement  respecting  the  places  in  which 
the  stem  of  the  plant  produces  gum  tragacanth,  but  also  respecting  the  season 
of  the  year  in  which  it  is  secreted,  as  well  as  the  aiding  of  the  secretion  by 
wounding  the  stem,  are  confirmed  a  century  later  by  Oliver  in  Persia,  nobody 
will  be  misguided  by  Sieber's  contradiction  of  Tournefort's  statement,  that  the 
plant  alluded  to  does  secrete  tragacanth  in  Crete.  If  Sieber  invokes  the  testi- 
mony of  Belon  in  support  of  his  view,  he  does  so  improperly  ;  for  Belon  (Obser- 
vat.,  p.  23)  merely  says  the  gum  is  collected 
|  We  have  thought  it  well  to  give  the  quotation  from  Tournefort  in  full. — 
Ed.  Ph.  J. 
a  #  *  *  Elle  donne  naturellement  de  la  gomme  Adragant  sur  la  fin  de  Juin, 
11 
