Botanical Source.—This plant is indigenous and perennial, with a simple or divided stem, more generally simple, slender, of a reddish color, from 4 to 7 inches in height. The leaves are linear-lanceolate, awn-pointed, entire, flattish, appressed, somewhat spreading, with the margins inflexed. The capsule is oblong, 4-sided, and the angles acute; the calyptra densely hairy and white; the lid or operculum short-beaked from a convex base; and the apophysis depressed and discoidal. The peristome is single, of 64 teeth, adherent by their summits to the membranous-dilated apex of the columella. Inflorescence dioecious; sterile flowers terminal and cup-shaped (W.—G.).
History.—This is an evergreen plant, found on high, dry places, along the margins of dry woods, and exposed places, mostly on poor, sandy soil, and is of a darker-green color than the mosses in general. The leaves are closely set on the stem about one-half its length, above which the stem is naked, terminating in a capsule, covered with a white, hairy hood or calyptre. The whole plant is medicinal. It yields its properties to boiling water by infusion. It has not been analyzed, but is deserving of chemical investigation. The similar species, P. formosum, according to Reinsch, contains fatty oil, a crystalline substance, resins, a trace of tannin, etc. (Wittstein, Handwörterbuch d. Pharmakogn. d. Pflanzenreichs, Breslau, 1882).
Action, Medical Uses, and Dosage.—This is a very valuable and important, but somewhat neglected, remedial agent. It is a powerful diuretic in strong infusion. In doses of 2 fluid ounces of the infusion, every 1/2 hour, it has been known to remove from a dropsical patient from 20 to 40 pounds of water in the space of 24 hours. It possesses but very little smell or taste, and never produces any nausea or disagreeable sensation in the stomach. It may be used in connection with hydragogue cathartics, or even alone, in dropsies, with the most decided advantage and is a very useful article in uric acid and phosphatic gravel, and other urinary obstructions, and especially urinal suppression from cold. Prof. Jones considered it worthy to be ranked among the first, if not at the head, of the class of diuretics. Notwithstanding the reputation of this plant, as a diuretic, I have known it frequently to fail in producing the slightest increase of the urinary discharge (J. King). A strong infusion of the fresh plant should be used when possible to obtain it; give specific polytrichum, 5 to 60 drops, every 1 to 3 hours.
King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.