Hedeo'ma pulegioi'des, (American) Pennyroyal. -- The dried leaves and flowering tops, U.S.P. 1830-1900; N. America, sandy fields, hills, open woods, scenting the atmosphere. Annual herb; stem 25-37.5 Cm. (10-15') high, quadrangular, pubescent, branched; root figrous, yellowish. Leaves opposite, 15-35 Mm. (3/5-1 2/5') long, thin, obtuse, obscurely serrate, glandular-hairy beneath, petiolate; flowers, axillary fascicles; calyx tubular, 5-toothed, bilabiate; corolla pale blue, spotted, bilabiate, containing 2 sterile and 2 fertile stamens; odor strong, mint-like; taste aromatic, pungent; solvents: alcohol, boiling water partially; contains volatile oil 1 p.c., bitter principle, tannin. Stimulant, carminative, emmenagogue, aromatic; flatulent colic, nausea, indigestion, corrective to purgatives; hot infusion -- diarrhea, bronchitis, rheumatism, amenorrhea (hot hip and foot baths); odor repulsive to fleas, mosquitoes, etc.; large doses, for suppressed catamenia or for inducing abortion, have occasioned death from narcosis. Dose, gr. 15-60 (1-4 Gm.); fluidextract (diluted alcohol), 3ss-2 (2-8 cc.); infusion, 5 p.c., 3ij (60 cc.), every hour; spirit (oil 1, + alcohol 9), externally and in spray. Volatile oil (oleum Hedeomae), U.S.P. 1820-1900, often added to liniments as a rubefacient. Mentha Pule'gium, European Pennyroyal, resembles closely the above, having oval, serrate leaves, and purplish flowers, cymes, corolla 4-lobed; Hedeoma piperi'ta, Mexico, is used for peppermint, while H. thymoi'des, Texas, having more agreeable odor, as aromatic, diaphoretic.