The leaves of Ledum latifolium, Aiton.
COMMON NAMES: Labrador tea, James' tea.
Botanical Source.—Ledum latifolium is an evergreen shrub, with an irregularly branched stem, from 2 to 5 feet in height. The branches are woolly. The leaves are alternate, subsessile, entire, 1 or 2 inches in length, nearly one-third as wide, obtuse, elliptical or oblong, smooth above, clothed with a dense, rusty wool beneath, and have revolute or replicate margins. The flowers are large, white, in dense, terminal corymbs of about a dozen flowers; the pedicels nearly as long as the leaves, filiform and pubescent. The calyx is very minute. Corolla white, consists of 5 spreading, obovate, obtuse petals. Stamens 5 or 10, as long as the petals; filaments slender and smooth; anthers small, opening by 2 simple, terminal pores. Ovary roundish; style straight, about as long as the stamens; stigma small and obtuse. Capsule ovate-oblong, subpubescent, 5-celled and 5-valved; valves splitting from the base upward, with the margins inflexed and connivent; and receptacles linear, extending into the cells of the capsule. The seeds are minute, terminating in a membrane at each extremity (L.—Torrey).
History and Chemical Composition.—This plant is a native of North America, and is found in the northern part of the United States and in Canada, growing in cold bogs and damp mountain woods, flowering in June and July. It is also found further south, growing on the mountains. The leaves are the parts used. They have a pleasant flavor, and yield their virtues to hot water in infusion, or to alcohol. It contains the glucosid ericolin (R. Thal, 1883). They were much employed instead of tea leaves during the Revolutionary War. Their medicinal virtues were well-known to the Cree Indians in the territory of the Hudson Bay, and to other Indian tribes.
Action, Medical Uses, and Dosage.—Ledum latifolium is pectoral and tonic, and, in small doses, is useful in coughs, irritations of the pulmonary membranes, and in dyspepsia. It increases the urinary flow. Reputed also to possess similar, but less energetic, properties than the Ledum palustre (see below), which is supposed to possess narcotic powers. An infusion of the leaves has been successfully employed in decoction in pertussis, dysentery, and to allay pruritic irritation in exanthematous diseases. In leprosy, itch, and several diseases of the skin, the decoction internally and externally has been beneficially used. Clothes, among which it is strewed, are said to be preserved from the ravages of moths. A strong decoction, used externally, will kill lice and other insects. Dose of the infusion of either of the above plants, from 2 to 4 fluid ounces, 3 or 4 times a day. A tincture may be prepared from the fresh leaves (℥viii to alcohol, 98 per cent, Oj). Dose, 1 to 10 minims.
Related Species.—Ledum palustre, Linné, or Marsh tea, also known as Marsh cistus, Wild rosemary, and Rosmarinus sylvestris, inhabits sphagnous swamps in the cold regions of the two continents, and may be distinguished by its linear leaves, having uniformly 10 stamens, and especially by its oval pods. The leaves have a pleasant, resinous odor, and a not unpleasant, amarous, and somewhat spicy taste, with slight astringency. They were formerly used in place of hops in the making of beer in some parts of Germany and Sweden. Water, by infusion, or alcohol, extracts the properties of ledum. Its chief proximate principles are: (1) Ericolin (C26H30O3, R. Thal, 1883), a resinous, bitter glucosid without odor, decomposing with water, or more rapidly with diluted mineral acids, into sugar and ericinol (C20H26O), which readily absorbs water and forms hydroericinol (C10H20O4), a thick fluid of a peculiar odor; (2) leditannic acid (C25H20O8); (3) volatile oil containing crystallizable ledum camphor (C15H25O, Rizza, Jahresb. Der Pharm., 1887, p. 363, and Hjelt, Chemiker Ztg., 1895, p. 2126), melting at 105° C. (221° F.). 0.7 per cent of the oil was obtained by Hjelt and Collan (1882) from the herb grown in wet localities. The flowering tops yielded (Schimmel & Co., Oct., 1894) 1.2 per cent of the oil, while the non-flowering shrub yields only about 0.35 per cent. The poisonous andromedotoxin was established, by Prof. Plugge and De Zaayer, to be absent from Ledum palustre (Amer. Jour. Pharm., 1889, p. 360).