Dirca palustris. Leather wood.
The diversity of climate in different latitudes of the United States does not prevent this shrub from appearing in the most rigorously cold as well as in the warmest sections of the country. I have seen it growing plentifully on the hanks of the Kennebec, in Maine, and Mr. Bartram found it in great vigour on the Savannah river in Georgia. It is a marshy shrub frequenting low woods and the vicinity of water, flowering in April and May. It is commonly of humble growth, though Mr. Bartram found specimens six or seven feet in height. It is remarkable for the flexibility of its wood and toughness of its bark, which are so great that it cannot be broken without great difficulty. The Aborigines employed it for their cordage, and from its great tenacity the name of Leather wood has been applied to it in most parts of the United States. The Canadian French called it Bois de Plomb or Leaden wood from its flexibility.
The generic character of Dirca consists in a tubular corolla without calyx, having its border obsoletely toothed. Stamens longer than the corolla. Berry one-seeded.
The genus contains but a single species.
Class Octandria, order Monogynia. Natural orders Vepreculae, Lin. Thymelaeae, Juss. The Dirca is an irregular shrub somewhat distinguished by the horizontal tendency of its branches and leaves. The branches have an interrupted or jointed mode of growth. The leaves are scattered or alternate, with very short petioles. They are oval, entire, subacute, downy, when young, smooth and membranous when fully grown, and pale on the under side. The flowers appear long before the leaves. Previously to their emerging they exist in miniature within a small hairy bud, which occupies a sheath or cavity in the end of each flowering branch. They are commonly in bunches of three together with their peduncles cohering. Each flower is about half an inch long, of a yellow colour and without calyx. The corolla is funnel-shaped, with a contraction near the base and another in the middle, its border dilated, and slightly and irregularly toothed. Stamens eight, much longer than the corolla, the alternate ones longest, the filaments capillary and inserted into the tube; the anthers roundish. Germ ovate placed obliquely, the style appearing to issue from one side. The style is capillary, curved, and longer than the stamens. The fruit is a small oval, acute, red, one-seeded berry.
Chemically examined, the bark of this shrub discovers a slightly resinous character by the pearliness which its tincture assumes on admixture with water. The decoction is somewhat mucilaginous and deposits slight flocculi on the addition of alcohol. Iron and gelatin produce no evidence of tannin or gallic acid. The distilled water has an unpleasant odour, but is void of acrimony.
The bark of the Dirca has a peculiar and rather unpleasant taste. When swallowed, it leaves a sensation of acrimony in the fauces which continues for some time. If taken in the quantity of six or eight grains, it produces a sense of heat in the stomach and at length brings on vomiting. This effect pretty certainly occurs if the bark be recent or freshly powdered.
A variety of observations on this shrub have been made by my pupil, Dr. John Locke, who first called my attention to the examination of its properties. He found on experiment that not only the distilled water, but the decoction also was void of acrimony, and that in the boiled bark this property was very much diminished, though still present. The watery extract had considerable bitterness, but scarcely any of the peculiar acrimony of the plant. Taken in doses of a drachm, it did not produce any very sensible effect. Alcohol without heat acquired but slight sensible properties from the bark. Nothing came over by distillation with alcohol, but the alcohol remaining in the retort had acquired the acrimony. The spirituous extract procured by evaporating this decoction was equal to one twenty fourth of the bark from which it was obtained. It contained the acrimony in a concentrated form, producing a more powerful effect on the fauces than the fresh bark. It was largely but not completely soluble in water.
Dr. Locke gave the freshly dried root to various patients in doses of from five to ten grains, which quantity in most instances proved powerfully emetic, and sometimes cathartic. It was found to be deteriorated by keeping, and did not produce the same effects when very old. In consequence of some statements which have been made in regard to its vesicating properties, Dr. Locke applied portions of the bark moistened with vinegar to the skin of his arm. In twelve hours no effect was produced, in twenty four some redness and itching took place and in thirty a complete vesication followed.
The fruit of the Dirca has been suspected of narcotic properties. Dr. Perkins, of Hanover, N. H. has communicated the case of a child which had eaten these berries with effects like those produced by Stramonium, such as stupor, insensibility, and dilatation of the pupils. An emetic brought up the berries and the child gradually recovered. A medical student who took several of the berries found that they produced nausea and giddiness.
The medicinal action of the bark of the Dirca probably depends on its acrid constituents, which appear to be partly of a resinous and partly of a volatile nature. Its properties appear somewhat allied to those of Polygala senega, for which it might perhaps be substituted in small quantities. It is best given in substance, though on account of the tenacity of its fibres it is difficult of subdivision. After beating in a mortar it resembles fine lint more than powder. Its vesicating properties appear too feeble to promise much utility.
I have introduced the Dirca in this place, not so much because it has been yet applied to any medical purpose of great importance; but because it would be improper, in a work like the present, to pass over unnoticed a shrub of such decided activity.
Dirca palustris, Lin. Amoenitates academicae, iii. t. 1. 6. 7.
Duhamel, Arb. vi. t. 212.
Pursh, 1. 236.
Michaux, 1. 268.
Bartram, Travels, 309.
Kalm, Travels, ii. 148.
B. S. Barton, Coll. 32.
American Medical Botany, 1817-1821, was written by Jacob Bigelow, M. D.