salts, and consists of crystals deposited in the oil of peppermint
distilled from the Japanese peppermint plant. This oil, when separated
from the crystals, is now largely used to flavor cheap peppermint
lozenges, being less expensive than the English oil. The crystals
deposit naturally in the oil upon keeping, but the Japanese extract
the whole of it by submitting the oil several times in succession to a
low temperature, when all the menthol crystallizes out from the oil
and falls to the bottom of the vessel. The source of the Japanese
peppermint oil has been stated to be Mentha arvensis, var. javanica.
On examining several specimens of this plant in our national herbaria
I found that the leaves tasted like those of the common garden mint
(Mentha viridis), and not at all like peppermint, and that therefore
the oil and menthol could not possibly be derived from this plant.

I then asked my friend, Mr. T. Christy, who takes great interest in
medicinal plants, to endeavor to get specimens from Japan of the plant
yielding the oil. After many vain attempts, he at last succeeded in
obtaining live plants. These were cultivated in his garden at Malvern
House, Sydenham, and when they flowered I examined the plant and found
that it differed from other forms of M. arvensis in the taste, in the
acuminate segments of the calyx of the flower, and in the longer leaf
stalks; the leaves also taper more toward the base. Dr. Franchet, the
greatest living authority on Japanese plants, to whom I sent
specimens, confirmed my opinion as to the variety deserving a special
name, and M. Malinvaud, a well known authority on mints, suggested the
name piperascens, which I adopted, calling the plant Mentha arvensis,
var. piperascens. Specimens of the plant kindly lent by Mr. Christy
for the purpose were exhibited by me at an evening meeting of the
Linnæan Society, and by a printer's error in the report of the remarks
then made, the name of the plant appeared in print as Mentha arvensis,