From the statistics quoted by Stearns[1775] it would appear that the produce of oil per acre is somewhat higher in America than in England, but from various causes information on this head cannot be very reliable.
Peppermint is cultivated at Sens in the department of the Yonne in France[1776] and in Germany in the environs of Leipzig, where the little town of Cölleda produces annually as much as 40,000 cwts. of the herb.
The annual crop of the world is supposed to yield 90,000 lb. of peppermint oil.[1777]
Peppermint oil varies greatly in commercial value, that of Mitcham commanding twice or three times as high a price as the finest American. Even the oil of Mitcham is by no means uniform in quality, certain plots of ground affording a product of superior fragrance. A damp situation or badly drained ground is well known to be unfavourable to the quantity and quality of oil.
The presence of weeds among the peppermint is an important cause of deterioration to the oil, and at Mitcham some growers give a gratuity to their labourers to induce them to be careful in throwing out other plants when cutting the herb for distillation. One grower of peppermint known to us was compelled to abandon the cultivation, owing to the enormous increase of Mentha arvensis L. which could not be separated, and which when distilled with the peppermint ruined the flavour of the latter. In America great detriment is occasioned by the growth of Erigeron canadensis L. Newly cleared ground planted with peppermint is liable to the intrusion of another plant of the order Compositæ, Erechtites hieracifolia Raf., which is also highly injurious to the quality of the oil.[1778]
Uses—A watery or spirituous solution of oil of peppermint is a grateful stimulant, and is a frequent adjunct to other medicines. Oil of peppermint is extensively consumed for flavouring and cordials.
HERBA PULEGII.
Pennyroyal[1779]; F. Menthe pouliot, Pouliot vulgaire; G. Polei.
Botanical Origin—Mentha Pulegium L., a small perennial aromatic plant, common throughout the south of Europe and extending northward to Sweden, Denmark, England and Ireland, eastward to Asia Minor and Persia, and southward to Abyssinia, Algeria, Madeira and Teneriffe. It has been introduced into North[1780] and South America. For medicinal use it is cultivated on a small scale.
History—Pennyroyal was in high repute among the ancients. Both Dioscorides and Pliny describe its numerous virtues. In Northern Europe it was also much esteemed, as may be inferred from the frequent reference to it in the Anglo-Saxon and Welsh works on medicine.