_Gummi Tragacantha_; _Tragacanth_, _Gum Tragacanth_; _F. Gomme
Adragante_; _G. Traganth_.
=Botanical Origin.=—Tragacanth is the gummy exudation from the
stem of several pieces of _Astragalus_, belonging to the subgenus
_Tragacantha_. The plants of this group are low perennial shrubs,
remarkable for their leaves having a strong, persistent, spiny petiole.
As the leaves and shoots are very numerous and regular, many of the
species have the singular aspect of thorny hemispherical cushions,
lying close on the ground; while others, which are those furnishing the
gum, grow erect with a naked woody stem, and somewhat resemble furze
bushes.
A few species occur in South-western Europe, others are found in Greece
and Turkey; but the largest number are inhabitants of the mountainous
regions of Asia Minor, Syria, Armenia, Kurdistan and Persia. The
tragacanth of commerce is produced in the last named countries, and
chiefly, though not exclusively, by the following species[704]:—
1. _Astragalus adscendens_ Boiss. et Hausskr., a shrub attaining 4
feet in height, native, of the mountains of South-western Persia at an
altitude of 9,000 to 10,000 feet. According to Haussknecht, it affords
an abundance of gum.