Peppermint; F. Menthe poivrée; G. Pfefferminze.
Botanical Origin—Mentha piperita Hudson (non Linn.), an erect usually glabrous perennial, much resembling the Common Spearmint of the gardens, but differing from it in having the leaves all stalked, the flowers larger, the upper whorls of flowers somewhat crowded together, and the lower separate. In the opinion of Bentham it is possibly a mere variety of M. hirsuta L., with which it can be connected by numerous intermediate forms.
Peppermint rapidly propagates itself by runners, and is now found in wet places in several parts of England, as well as on the Continent. It is cultivated on the large scale in England, France, Germany, and North America.
History—Mentha piperita was first observed in Hertfordshire by Dr. Eales, and communicated to Ray, who in the second edition of his Synopsis Stirpium Britannicarum, 1696, noticed it under the name of Mentha spicis brevioribus et habitioribus, foliis Menthæ fuscæ, sapore fervido piperis; and in his Historia Plantarum[1763] as “Mentha palustris ... Peper-Mint.”[1764] Dale, who found the plant in the adjoining county of Essex, states[1765] that it is esteemed a specific in renal and vesical calculus; and Ray, in the third edition of his Synopsis, declares it superior to all other mints as a remedy for weakness of the stomach and for diarrhœa. Peppermint was admitted to the London Pharmacopœia in 1721, under the designation of Mentha piperitis sapore.
The cultivation of peppermint at Mitcham in Surrey dates from about 1750,[1766] at which period only a few acres of ground were there devoted to medicinal plants. At the end of the last century, above 100 acres were cropped with peppermint. But so late as 1805 there were no stills at Mitcham, and the herb had to be carried to London for the extraction of the oil. Of late years the cultivation has diminished in extent, by reason of the increased value of land and the competition of foreign oil of peppermint.
On the Continent Mentha Piperitis was grown as early as 1771 at Utrecht; Gaubius[1767] appears to have been the first to notice “Camphora Europæa Menthæ Piperitidis,” i.e. Menthol ([see page 483]).
In Germany peppermint became practically known in the latter half of the last century, especially through the recommendation of Knigge.[1768]
Description—The rootstock of peppermint is perennial, throwing out runners. The stem is erect, 3 to 4 feet high, when luxuriant somewhat branched below with erecto-patent branches, firm, quadrangular, slightly hairy, often tinged with purple. Leaves all stalked, the stalks of the lower ½ to ¾ of an inch long, naked or nearly so, the leaf lanceolate, narrowed or rather rounded towards the base, the point narrowed out and acute, the lowest 2 to 3 inches long by about ¾ of an inch broad, naked and dull green above, paler and glandular all over, but only slightly hairy upon the veins beneath; the teeth sharp, fine, and erecto-patent. Inflorescence in a loose lanceolate or acutely conical spike, 2 to 3 inches long by about ¾ of an inch broad at the base, the lowest whorls separate, and usually the lowest bracts leaf-like. Bracteoles lanceolate-acuminate, about equalling the expanded flowers, slightly ciliated. Pedicels 1 to 1½ lines long, purplish, glandular but not hairy. Calyx often purplish, the tube about 1 line long and the teeth ½ a line, the tube campanulate-cylindrical, purplish, not hairy, but dotted over with prominent glands; the teeth lanceolate subulate, furnished with short erecto-patent hairs. Corolla reddish-purple about twice as long as the calyx, naked both within and without. Nut smooth[1769] (rugose, according to our observation). The odour and taste are strongly aromatic.
In var. 2. vulgaris of Sole, M. piperita β. Smith, the plant is more hairy, with the spikes broader and shorter, or even bluntly capitate. colourless, pale yellow, or greenish liquid, of sp. gr. varying from 0·84 to 0·92. We learn from information kindly supplied by Messrs. Schimmel and Co., Leipzig, that the best peppermint grown in Germany, carefully dried, affords from 1 to 1·25 per cent. of oil. It has a strong and agreeable odour, with a powerful aromatic taste, followed by a sensation of cold when air is drawn into the mouth. We find that the Mitcham oil examined by polarized light in a column 50 mm. long, deviates from 14°·2 to 10°·7 to the left, American oil 4°·3.
Chemical Composition—The constituent for the sake of which peppermint is cultivated is the essential oil, Oleum Menthæ piperitæ, a coloureless, pale yellow or greenish liquid, of sp. gr. varying from 0·84 to 0·92. We learn from information kindly supplied by Messrs. Schimmel and Co., Leipzig, that the best peppermint grown in Germany, carefully dried from 1 to 1·25 per cent of oil. It has a strong and agreeable odour, with a powerful aromatic taste, followed by a sensation of cold when air is drawn into the mouth. We find that the Mitcham oil examined by polarized light in a column 50 mm. long, deviates from 14·2° to 10·7° to the left, American oil 4·2°.