240 r MEDICAL BOTANY. 



destitute of it, and the same takes place with the Liquidambar, as in Georgia, 

 &c.,it affords large quantities of balsam, whilst in Pennsylvania this secretion 

 is almost wanting in it. 



All the spiny species of Astragalus possess the same general appearance 

 and characteristics, and form so natural a group, that it was proposed by 

 some botanists to erect them into a genus under the name of Tragacantha. 

 They are, without exception, small shrubs, with very numerous branches, 

 covered with imbricated scales, and beset with spines. So great is their ana- 

 logy and resemblance, that Linnaeus considered them as varieties of one spe- 

 cies. The more recent researches of Pallas, Liedebour, and De Candolle, 

 have shown the error of this amalgamation ; though it must be confessed that 

 the characters assigned to these species are vague and unsatisfactory, and 

 may arise rather from climate and situation than from any inherent difference 

 in the plants. In fact, the confusion that exists in the synonymy is so great, 

 that it has become almost impossible to ascertain what species really exist, and 

 what are founded on varieties. Thus, the original A. tragacantha of Linnseus is 

 the A. massiliensis of Lamarck, and the A. massiliensis of the former is the 

 A. aristatus of Villars, though not perhaps of Sieber or Sibthorp. The-^4. 

 tragacantha of Hablizt is the A. poterium of Pallas; the A. creticus of 

 Lamarck is the A.echinoides of Willdenow, and the A. gummifer of Labil- 

 lardiere is the A. caucasicus of De Candolle, &c. From this confusion it 

 becomes almost impossible to decide what species furnish the gum of com- 

 merce, though it is certain it is from the spinous kinds only. The London 

 College and the United Stales Pharmacopoeia have followed Olivier in as- 

 cribing it to the A. verus, and the Edinburgh to the A. gummifer, in accor- 

 dance to the opinion of Labillardiere. The species which are generally ad- 

 mitted are four, and will, therefore, be noticed separately. 



1. A. verus, Olivier. — Flowers axillary, in clusters of 2 — 5, sessile. Calyx tomentose, 

 obtusely 5-toothed. Leaflets 8 — 9 pairs, linear, hispid. 



Olivier, Voyage, iii. t. 44 ; De Candolle, ii. 296 ; Lindley, Fl. Med., 247. 



This species is found in Asia Minor, Armenia, and Persia, and is stated by 

 Olivier [Voyage dans V Empire Ottoman, iii. 44) to afford the largest propor- 

 tion of the gum sent to Europe. It, like the others, is a low shrub, and very 

 hispid. 



2. A. gummifer., Labillardiere. — Flowers 3 — 5, axillary, sessile. Calyx 5-cleft, and 

 with the legumes woolly. Leaflets 4 — 6 pairs, oblong, linear, smooth. 



Labill., Journ. Phys., 1790; De Candolle, Prod., ii. 296; Lindley, Fl. 

 Med., 247. 



It is a native of Syria and Koordistan, and, according to Lindley (Bot. 

 Reg., 1840), who received specimens of it from the English consul at Erze- 

 roun, is the plant furnishing the best kind of tragacanth. 



F 'g- 12 4- 3. A. creticus, Tournefort. — Flowers axillary, 



sessile, clustered. Calyx 5-partite, with setaceous 

 lobes, rather longer than the corolla. Leaflets 5 — 8 

 pairs, oblong, acute, tomentose. 



Lamarck, Diet., i. 321 ; De Candolle, As- 

 trag., t. 38 ; Lindley, Fl. Med., 248. 



This grows in Crete, where it was found 

 by Tournefort, and considered by him to be 

 the source from whence the gum was obtain- 

 ed. There is little doubt that this is the spe- 

 a. creticus. cies alluded to by the ancient writers, though 



Dr. Sibthorp is of opinion that it was the next. 



