The Japanese Peppermint Plant.

By E. M. HOLMES, F.L.S.,

Curator of the Museum of the Pharmaceutical Society of Great Britain.

When examining some leaves of this plant, presented, together with a series of Japanese drugs, to the Museum of the Pharmaceutical Society, by Messrs. Christy & Co., in 1879, I thought it desirable to compare them with those of the plant which is stated to yield the Chinese oil of peppermint. Through the courtesy of the keeper of the Kew Herbarium, I was permitted to taste a fragment of a leaf of the Chinese plant and one of Blume's specimens of M. arvensis, L., var. Javanica, the plant to which this peppermint is referred in "Pharmacographia." To my surprise I found that neither Blume's specimen nor any others of the same plant from various localities had the taste of peppermint, but possessed a flavor similar to that of the garden mint (M. viridis). Judging that the Japanese plant could not belong to M. arvensis, var. Javanica, I referred to the Japanese work "Zo Mokou Zoussetz," in which the Japanese peppermint plant is stated to be Mentha arvensis, var. vulgaris, Benth. On tasting the type specimen of this plant at Kew, I found that this also did not possess the taste of peppermint, but only that peculiar to European specimens of M. arvensis. I therefore wrote to China and Japan for specimens of the peppermint plants of those countries. After the lapse of more than a year, Mr. C. Ford, the Director of the Botanical Gardens at Hong Kong, was able to procure a flowering specimen of the Chinese plant for me, but no specimens of the Japanese plant could be procured by my correspondents. Mr. T. Christy, however, after having first obtained seeds of the plant, attempted to grow them, without success, but was ultimately, and after considerable difficulty, able to procure from Japan living plants which flowered this year in his garden at Sydenham, and a specimen of the plant was exhibited for the first time, I believe, in this country, at the meeting of the Pharmaceutical Conference, at Southampton. On careful examination, both the Chinese and Japanese plants thus obtained were found to possess the botanical characters of Mentha arvensis, as defined in DeCandolle's "Prodromus;" the leaves being stalked, ovate lanceolate, and the hairs on the stems and pedicels reflexed, those of the calyx being erecto-patent, and those of the upper surface of the leaf appressed, the calyx being bell-shaped with acute lanceolate or narrowly-triangular teeth. The Chinese plant differs from the Japanese one in the leaves being narrower in proportion to their length and in the calyx teeth being shorter and more broadly triangular. In outline, the leaves of both plants taper more to the base and have a longer petiole than the English forms of M. arvensis, coming very near to M. canadensis in this feature. The latter plant however, has spreading hairs on the stem. The Chinese plant appeared to so nearly resemble M. canadensis, var. glabrata, that I applied to Professor Asa Gray for specimens of that species for comparison. The specimens of M. canadensis which he kindly forwarded to me were derived from. different localities in the United States, and varied considerably in taste and appearance, some having the flavor of pennyroyal, others that of M. viridis, and others again that of peppermint, in a feeble degree. The specimen having a peppermint flavor is labeled M. canadensis, var. glabrata; it has reflexed hairs on the stem, and differs from the typical plant in having more triangular and shorter calyx teeth, which, as well as the petioles, have erect hairs; in fact, it appears in every respect to be the same plant as that grown at Canton. It is not surprising, however, to find Japanese or Chinese plants extending to North America.

It appears, then, that there are two plants possessing a widely different taste and both referred to M. arvensis, var. Javanica, by botanists. This might lead to confusion if the Chinese or Japanese peppermint plants ever came into demand for purposes of cultivation, unless a special name be given to the form which possesses the peppermint flavor, even although it does not possess characters sufficiently definite to separate it from M. arvensis. The mints are well known to form an uninterrupted series of plants which it is difficult to separate into species. Deeming it advisable, therefore, before giving it a name, to consult those botanists who have critically studied the mints, specimens of the Japanese peppermint plant were forwarded to several authorities on the genus, and the following opinions have been expressed: Mr. J. G. Baker, of the Kew Herbarium, considers it to be a form of Mentha sativa, Sm. (It may be here remarked that this form, as recognized by Hooker and Babington in their "British" Floras, is a species differing from M. arvensis in the smaller upper leaves and longer calyx teeth, while De Candolle includes it under M. arvensis.) Professor Baillon, of Paris, expresses the opinion that it must be referred to M. arvensis, var. Javanica, unless it be a hybrid between M. arvensis and M. piperita. Dr. Garcke, of Berlin, finds the plant to be nearly allied to Mentha canadensis, D.C., and also to M. aquatica, var. subspicata, D.C. Dr. Franchet, one of the authors of the most recent "Flora" of Japan, believes the Japanese plant to be "a form of M. arvensis, characterized by the acuminate calycine segments, a feature which constantly occurs in specimens from eastern Asia." He adds, After carefully comparing your specimen and having vainly sought an analogous taste in the different forms of the M. arvensis of Europe, I have found in them only an insipid and herbaceous flavor; I can say the same of M. arvensis from the neighborhoods of Pekin and Chefu, in the province of Shantung, and from the neighborhood of the lake Sitau, in the province of Sche-kimy; but I find the taste of peppermint developed in a very high degree in a specimen gathered at Voosung, near Shanghai. From Japan I possess specimens of M. arvensis gathered in very many localities, and I have found the taste of peppermint in all my specimens, without exception. This taste is absolutely the same as that furnished by your plant. I remark, however, that the taste is more pronounced in proportion as the plants are more robust; puny specimens with small leaves from Kanasawa (in Nipphon) possess it only in a feeble degree." He thinks that the peppermint flavor is not the result of hybridity, Since no other species has hitherto been observed in Japan, either in a cultivated or wild state, except M. crispa ("So Mokou Zoussetz," xi, pl. 29) (which no botanist, that he is aware of, has ever brought back from that country), and M. gentilis, which is well delineated under the name of' M. arvensis on the same page as M. piperita, after information probably furnished by the Dutch. M. Malinvaud remarks that the name piperita cannot be appropriated to the Japanese plant, as it is already applied to a form of M. arvensis with flower spikes. He therefore suggests the name Mentha arvensis, var. piperascens.

The weight of opinion is, therefore, on the side of considering the Japanese plant as a form of Mentha arvensis, D.C. If M. sativa, Lin., and M. arvensis, as defined by Babington, as well as M. Javanica, D.C., are to be considered as forms of one species, then the Japanese plant might, I think, also rank as a form under the name of M. arvensis f. piperascens, differing from M. arvensis as described by Babington in having the calyx teeth longer than broad, and in the upper leaves being gradually smaller; from M. sativa, in the leaves having longer stalks and tapering below; from M. Javanica, in the uppermost leaves being more than twice (usually six or eight times) as long as the verticillasters, and in the veins being hairy on the under surface of the leaf whilst those on the calyx are erecto-patent; and from M. canadensis, in the reflexed pubescence of the stems.

With respect to the Chinese peppermint plant, it so exactly agrees with the specimen of Mentha canadensis, var. glabrata, furnished to me by Dr. A. Gray, that if the latter be a typical specimen (Dr. Franchet notes, in his " Flore du Japan," the reflexed leaves in some specimens of M. canadensis.) I can only consider that it should be referred to M. arvensis, under the name of M. arvensis, var. glabrata.

Dr. Gray's specimen has the calyx teeth much shorter than those of the typical M. canadensis sent at the same time, and the hairs on the stem and pedicels are reflexed, while those of the calyx tube are erecto-patent.

There are some other points in connection with peppermint which are extremely suggestive, and to which I desire to call the attention of those who have greater ability and more time for investigation than myself.

A number of varieties and forms of so-called species possess the same odor and flavor, as shown in the following list:

Mentha piperita, Mentha arvensis., var. piperascens, M. canadensis, var. glabrata (!), and M. incana (!), cultivated near Bombay for producing peppermint oil (Dymock).

Spearmint, Mentha viridis, L., Mentha sylvestris (!), rotundifolia (!), sylvestris (!), canadensis (!), M. arvensis, (Those marked (! ) have been tasted by myself—E. M. HOLMES.) var.

The questions then arise:

1st. Do the oils of these species differ among themselves, as has been shown to be the case with those of M. piperita and M. arvensis, var. piperascens ? ("Pharm. Jour." (3), 11, p. 321.)
2d. If so, is this difference dependent on degree of development, on climate, soil, (Mr. J. Lloyd found a variety of M. aquatica possessing a lemon odor on calcareous soil near the sea, and M. Malinvaud a specimen of M. arvensis with a lemon odor in a ditch near Ivry, where other plants of the same species possessed only the usual odor of the plant.—Bull. Soc. Bot., 1881, p. 370.) or sex?
3d. Is the oil in each case a mixture, in which one ingredient is present in variable quantity in the different plants?
4th. Do the oils of spearmint and peppermint bear any chemical relation to each other?
5th. Which species, containing the oil of peppermint, yields the largest quantity and which the most valuable one for medicinal purposes ?

To recapitulate: The writer would recommend that for convenience the name of Mentha arvensis f. piperascens should be retained for the Japanese peppermint plant and that of Mentha arvensis f. glabrata for the Chinese one.—Phar. Jour. and Trans., Nov. 11, 1882.

The American Journal of Pharmacy, Vol. 55, 1883, was edited by John M. Maisch.