This tree is forty or fifty feet high, and much branched. Its leaves are winged, with five pair of leaflets, somewhat oval, pointed, smooth, and of pale green colour. The flowers are large, yellow, and grow in oblong clusters. The pods are divided, by transverse partitions, into numerous cells, each containing one seed.
These pods are in request on account of the black, sweetish, but somewhat acid pulp, which is contained in their cells, and which is used, in many cases, as a mild opening medicine. It is customary in Egypt to pluck the pods before they are quite ripe, and to place them in a house, from which the external air is, as much as possible, excluded. They are then laid in beds about six inches deep, having palm leaves interposed betwixt them. On the two following days the whole are sprinkled with water; and, in the course of about six weeks, they are in a fit state to be packed for sale.
The East Indian and West Indian cassia somewhat differ, both in appearance and qualities. Of the former the pods are smoother, smaller, and have a thinner rind; and the pulp is of a deeper shining black colour, sweeter, and more agreeable to the taste. In choosing cassia, those pods should be selected which are the heaviest, and in which the seeds do not rattle on being shaken.
138. LIGNUM VITÆ and GUIACUM are the wood and resin of a large West Indian tree (Guiacum officinale, Fig. 77) which has winged leaves in two sets upon one footstalk, and regular flowers of five petals.
The usual height of this tree is between thirty and forty feet. The leaves consist of two, three, and sometimes four pairs of leaflets, which are somewhat oval, and of shining dark green colour. The flowers spring, in clusters, from the division of the smaller branches; the petals are of a rich blue colour, and the stamens are crowned with yellowish anthers.
The wood, resin, bark, and even the flowers of this tree, are all of use either in the mechanical arts or in medicine. The former, which is yellow towards the outside, of deep blackish brown colour in the centre, and so compact and heavy as to sink, when immersed in water, is chiefly employed in the West Indies for the wheels and cogs of sugar mills. It is also formed into mortars, bowls, and domestic utensils of various kinds, for which, on account of its hardness, and not being liable to warp, it is peculiarly valuable. Lignum vitae is chiefly imported into this country from Jamaica, in logs or pieces of four or five hundred pounds' weight each, and is in great request for school-boys' rulers, and numerous articles of turnery ware. A decoction of the wood, when rasped, is occasionally administered as a medicine in rheumatic and gouty affections.
The resin of this tree is sometimes obtained by wounding the bark in different parts. It exudes through the wounds; and, when sufficiently hardened by exposure to the sun, is taken off, and packed in small kegs for exportation. Sometimes it is obtained by sawing the wood into billets, each about three feet in length, which are then bored with an augur longitudinally, and laid upon a fire, in such position that the melted resin, which flows through the hole as the wood burns, may be received into a vessel placed for the purpose of containing it. This resin, which is frequently called gum guiacum, is of a greenish colour, but has sometimes a reddish hue. Its taste is pungent and acrid. From the bark of the tree there is frequently a spontaneous exudation: this has the name of native gum, and is imported in small, irregular, bright pieces, which are much more pure than the gum obtained in any other way. Guiacum is used as a strengthening medicine, and a warm aromatic; it is employed as a remedy against rheumatic and other pains, and as an ingredient in many officinal preparations. On its first introduction, which was soon after the discovery of America, it was in such repute as to have been sold for seven crowns a pound.
In the West Indies, the bark, flowers, and fruit, are each employed in medicine; and of these the former is frequently used instead of soap for washing, in which process it gives a good lather.
139. BALSAM OF TOLU is a reddish yellow, thick, and pellucid substance, of fragrant odour, which is obtained from a tree (Toluifera balsamum) which grows in South America.
This tree is of considerable height; and has somewhat oval leaves, each on a short foot-stalk. The flowers are numerous, and in lateral branches; and the fruit is a round berry.