658 



HISTORY OF THE VEGETABLE KINGDOM. 



The astragalus tragacanth, is a low, procum- 

 bent shrub, with a short, tliick, branched stem, 

 clothed with brown, rigid fibres, and beset with 

 long sharp spines. The leaves are pinnated, 

 consisting of about eight pairs of small, oblong 

 leaflets, which are attached to a strong, spinous, 

 persistent footstalk, or midrib. The flowers are 

 large, papilionaceous, of a pale yellow colour, 

 and terminate the branches in close clusters. 

 The pod is two-celled, containing kidney-shaped 

 83eds. It is a native of Asiatic Turkey, and the 

 southern part of Europe, particularly Italy, 

 Sicily, and Crete; and it flowers from May till 

 July. 



It was introduced into England in the time 

 of Parkinson, where it thrives well, but does 

 not produce any gum. Tournefort discovered 

 it growing plentifully about Mount Ida. Accord- 

 ing to his observations, the gum exudes spon- 

 taneously towards the end of June, and in the 

 following months, during which period the nutri- 

 tious juice of the plant, thickened by the sum- 

 mer heat, bursts most of the vessels in which it 

 is confined. This juice coagulates in threads, 

 which make their way into the pores of the 

 •bark, through which being jiushed forward by 

 fresh juice they issue forth, and are at length 

 hardened in the air, cither in irregular lumps, or 

 in long vermicular pieces bent into a variety of 

 shapes. The best sort is white and semi-trans- 

 parent, dry, but somewhat soft to the touch. It 

 is considerably different in many of its properties 

 from gum Arabic; one part of this diff'used in one 

 hundred parts of water, affords a fluid of the 

 same consistency as one part of gum Arabic dis- 

 solved in ten parts of water. Water is, however, 

 but an imperfect solvent of it, not forming the 

 same intimate union with it as with other gums. 

 When tragacanth is put into water, it slowly 

 imbibes a great quantity, swells into a large 

 volume, and forms a soft, but not fluid mucilage. 

 On the addition of more water, and if the mix- 

 ture be agitated, the gum will be more generally 

 diffused throughout the liquor, which will appear 

 turbid. If left at rest, the mucilage will again 

 separate and subside; the supernatant water 

 appearing limpid, and holding only a very small 

 portion of the gum. 



This mucilage differs from that of gum Arabic 

 in being precipitated by sugar of lead, and the 

 oxymuriate of tin, and not by silicated potass, 

 or the oxysulphate of iron. 



M. Billardier gives a somewhat different 

 account from that of Tournefort. He says that 

 he visited Mount Lebanon in August, the season 

 when the gum is collected. He then found the 

 species of astragalus which afforded it to be 

 different from that figured and described by 

 Tournefort. According to Billardier, the stem 

 of the Cretan astragalus is blackish, that of 

 Lebanon is yellow; the leaves of the first are 



downy, of the second they are smooth; the flowers 

 of one are red, of the other of a pale yellow. 

 From whence he infers, that there are two or 

 more species of this plant which afford the gum. 

 He also dissents from tlie opinion of Tournefort, 

 who attributes the flowing of the gum to the 

 contraction of the fibres of the bark, occasioned 

 by the intensity of the solar heat, observing, 

 that it is only during the night, or when the 

 sun is obscured by clouds, that the gum issues 

 from the plant, and that the same has been 

 remarked at Crete. 



Astragalus verus is a native of the north of 

 Persia, and flowers in July and August. It is 

 a shrub of two or three feet in height, with a 

 stem about an inch thick, with many branches 

 closely crowded together, and covered with 

 imbricated scales and spines, formed from the 

 petioles of the former year. The leaves, which 

 scarcely exceed half an inch in length, are com- 

 posed of from six to eight pinnae, in opposite 

 pairs, villous, stiff, and pointed. The flowers 

 are small, yellow, and proceed from the axillse 

 of the leaves, with cottony brackets. The gum 

 exudes in summer, more or less plentifully in 

 proportion to the solar heat, in tortuous threads, 

 which are allowed to dry on the plant before 

 being collected. A great proportion of the gum 

 gathered in Persia, is sent to India, Bagdad, 

 Bassorah, and Russia. That which comes to 

 Britain, is sent from Aleppo, packed in cases. 



Gum tragacanth possesses the same demulcent 

 qualities as gum Arabic; and from its greater 

 viscidity, may in some cases be preferable. 



It is also used in preparing cloths for receiving 

 the dye, especially such mordants as are prepared 

 with nitrous acid. Its use, however, is restricted 

 in consequence of its high price. The annual 

 consunipt in Britain is about 30,000 lbs. 



A species of gum designated kuteera, was in 

 1802, and during a few previous jears, imported 

 in large quantities from India into Europe, under 

 the mistaken opinion that it was gum tragacanth, 

 which it so much resembled as to deceive many 

 dealers. It was, however, at length ascertained 

 that the kuteera was the product of the sterculia 

 urens, a tree abounding in several parts of Oude, 

 and the adjacent countries, but of quite a dif- 

 ferent species to the thoniy bush which yields 

 tragacantli. 



It is found that this substance does not possess 

 all the characteristics of gum, it being very 

 imperfectly soluble, and possessing little of a 

 glutinous nature; it is therefore inapplicable to 

 tlic purposes for which tragacanth is used. On 

 this dissimilarity being discovered, of course 

 this new gum was supposed to be valueless, and 

 many tons were for a long time lying at tlie 

 East India Company's warehouse totally unsale- 

 able. It might, however, l)e usefully applied to 

 some other purpose. The natives of India make 



