Order XL. Labiatae, Jussieu.—Labiates.
Characters.—Calyx tubular, inferior, persistent, the odd tooth being next the axis; regular 5- or 10-toothed, or irregular bilabiate or 3-to 10-toothed. Corolla monopetalous, hypogynous; bilabiate; the upper lip undivided or bifid, overlapping the lower, which Fig. 305. is larger and 3-lobed. Stamens 4, didynamous, inserted upon the corolla, alternately with the lobes of the lower lip, the 2 upper sometimes wanting; anthers 2-celled; sometimes apparently unilocular in consequence of the confluence of the cells at the apex: sometimes one cell altogether obsolete, or the 2 cells separated by a bifurcation of the connective. Ovary deeply 4-lobed, seated in a fleshy hypogynous disk; the lobes each containing 1 erect ovule; style 1, proceeding from the base of the lobes of the ovary; stigma bifid, usually acute. Fruit, 1 to 4 small nuts, inclosed within the persistent calyx. Seeds erect, with little or no albumen; embryo erect; cotyledons flat. Herbaceous plants or undershrubs. Stem 4-cornered, with opposite ramifications. Leaves opposite, divided or undivided, without stipules, replete with receptacles of aromatic oil. Flowers in opposite, Bilabiate flower. nearly sessile, axillary cymes, resembling whorls; sometimes solitary, or as if capitate (Lindley).
Properties.—The medicinal activity of the plants of this family depends on volatile oil, bitter extractive, and astringent matter.
The volatile oil resides in small receptacles (by some called globular glands) contained in the leaves. "These glands are placed quite superficially, or rather in depressed points, and are commonly of a shining yellow colour. We may regard them as oleo-resinous matter separated from glands lying on the under surface. When macerated in strong spirit of wine they remain unchanged, and appear under the microscope as transparent, probably cellular, vesicles, filled with a yellow granular matter." [Nees and Ebermaier, Handb. Med.-Pharm. Bot. Th. i. S. 524.]
The bitter extractive is found, in a greater or less quantity, in all the Labiatae. It is this principle which communicates the bitterness to the watery infusion of these plants.
The presence of astringent matter is shown by the green colour produced when a ferruginous salt is added to the infusion of some of the Labiatae.
The volatile oil gives to these plants aromatic, carminative, and slightly stimulant properties. The bitter extractive renders them tonic and stomachic. The astringent matter is usually in too small a quantity to communicate much medicinal activity, though it must contribute to the tonic operation.
The perfumer uses some labiate plants on account of their fragrant odour; the cook employs others for their flavour and condimentary properties; the medical practitioner administers them to relieve nausea and colicky pains, to expel wind, to cover the taste of nauseous medicines, and to prevent or relieve griping pains.
The following species, enumerated by London, [Encyl. of Gardening.] are cultivated in this country as sweet herbs: Common or Garden Thyme (Thymus vulgaris, Linn.), Lemon Thyme (T. citriodorus, Schreb.), Sage (Salvia officinalis, Linn.), Clary (S. Sclarea, Linn.), Peppermint (Mentha piperita, Linn.), Spearmint (M. viridis, Linn.), Pennyroyal (M. Pulegium), Common Marjoram (Origanum vulgare, Linn.), Winter Sweet Marjoram (O. heracleoticum, Linn.), Sweet Marjoram (Majorana hortensis, Moench.), Pot Marjoram (M. Onites, Benth.), Winter Savory (Satureja montana, Linn.), Summer Savory (S. hortensis, Linn.), Sweet or Larger Basil (Ocimum Basilicum, Linn.), Bush or Least Basil (O. minimum, Linn.), Rosemary (Rosmarinus officinalis, Linn.), and Garden Lavender (Lavandula vera, De Cand.). Some of these species have been, or are, used in medicine, and several of them are officinal.
Besides the labiate plants contained in the British pharmacopoeias and to be noticed, a considerable number of other species have been at different times introduced into medicinal use. Some of these are deficient in volatile oil, but abound in a bitter principle, on which account they have been employed as stomachics and tonics; such are Water Germander (Teucrium Scordium, Linn.), Wall Germander (T. Chamaedrys, Linn.), and Ground Pine (Ajuga Chamaepitys, Smith); the two last of which have been used, as I have before mentioned, as anti-arthritic remedies (see ante, p. 387). Others abound in essential oil. and are consequently more aromatic, stimulant, and carminative; such are Cat-Thyme (Teucrium Marum, Linn), Common Hyssop (Hyssopus officinalis, Linn.), Dittany of Crete (Amaracus Dictamnus, Benth.), &c. Teucrium Polium has been used in diarrhoea, dysentery, and cholera.