THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[SECOND SERIES.] 

 No. 117. SEPTEMBER 185?. 



XV, — Researches on the mode in which Gum-Tragacanth is 

 formed. By Hugo von Mohl*. 



The examination of Tragacanth gum possesses some theoretical 

 interest, for it is connected with many difficult and as yet ob- 

 scure points in the anatomy and physiology of plants. 



Tournefortf was the first of those to whom we are indebted 

 for exact observations on the secretion of gum-tragacanth from 

 one of the plants furnishing this substance. His observations 

 were made on Astragalus creticus, Lam., on Ida in Crete J. Ac- 

 cording to the figure which he gives, the stem of the said traga- 

 canth-plant attains a thickness of about 1 inch. The exudation 

 of the tragacanth, in the form of coiled threads, takes place at 

 the end of June and in the succeeding months. 



Tournefort regarded tragacanth as the sap inspissated by the 

 heat, which burst the vessels and poured itself out in the middle 

 {le cceur) of the stem and branches, as well as in the medullary 

 rays (dans Pinterstices des fibres, lesquelles sont disposees en 



* Botanische Zeitung, Jan. 16, 1857. Translated by Arthur Henfrey, 

 F.R.S. &c. 



t Relation d'un Voyage au Levant, i. 22. Amsterd, 1718. 



X Sieber (Reise nach Kreta, ii.68) has endeavoured to prove that Tourne- 

 fort's statement is altogether incredible, for, according to his investiga- 

 tions in Crete, no tragacanth at all is secreted from the plant above named; 

 but since not only Tournefort's statements regarding the parts of the 

 stems in which the tragacanth is formed agree perfectly with my investi- 

 gations, but his indication of the season at which the tragacanth exudes, 

 as well as of the furtherance of the exudation resulting by making inci- 

 sions in the stems, are confirmed by the observations made a century later 

 by Olivier in Persia, — no one will be led to doubt, on such authority, 

 Tournefort's statement that the said plant secretes tragacanth in Crete. 

 When Sieber refers to the testimony of Belon, he makes a mistake, for 

 Belon (Observat. p. 23) only says that no gum is collected on Mount Ida. 



Ann. ^ Mag. N. Hist. Ser. 2. Vol xx. 11 



