_Spearmint._
=Botanical Origin=—_Mentha viridis_ L. is a fragrant perennial plant,
chiefly known in Europe, Asia and North America, as the Common Mint
of gardens, and only found apparently wild in countries where it has
long been cultivated. It occurs occasionally in Britain under such
circumstances.[1756]
[1752] On the high land between Nice and Turbia, I have observed the
two species growing together, and that _L. vera_ is in flower two or
three weeks earlier than _L. Spica_.—D. H.
[1753] _De distillatione_, Romæ, 1608. 87.
[1754] The incorrectness of the term _Arabica_ is noticed by Pomet. How
it came to be applied we know not.
[1755] Pereira, _Elem. of Mat. Med._ ii. (1850) 1368.—Nor do we know
if _L. lanata_ Boiss., a very fragrant species closely allied to _L.
Spica_ DC., and a native of Spain, is distilled in that country.
[1756] Bentham, _Handbook of the British Flora_, 1858. 413.—Parkinson
(1640) remarks of _Speare Mint_ that it is “onely found planted in
gardens with us.”
_Mentha viridis_ is regarded by Bentham as not improbably a variety
of _M. silvestris_ L., perpetuated through its ready propagation
by suckers. J. G. Baker remarks, that while these two plants are
sufficiently distinct as found in England, yet continental forms occur
which bridge over their differences.[1757]
=History=—Mint is mentioned in all early mediæval lists of plants, and
was certainly cultivated in the convent gardens of the 9th century.
Turner, who has been called “the father of English botany,” states in
his _Herball_[1758] that the garden mint of his time was also called
“_Spere Mynte_.” We find spearmint also described by Gerarde who terms
it _Mentha Romana_ vel _Sarracenica_, or _Common Garden Mint_, but his
statement that the leaves are _white_, _soft_, and _hairy_ does not
well apply to the plant as now found in cultivation.
=Description=—Spearmint has a perennial rootstock which throws out
long runners. Its stem 2 to 3 feet high is erect, when luxuriant
branched below with short erecto-patent branches, firm, quadrangular,
naked or slightly hairy beneath the nodes, often brightly tinged with
purple. Leaves sessile or the lower slightly stalked, lanceolate or
ovate-lanceolate, rounded or even cordate at the base, dark green and
glabrous above, paler and prominently veined with green or purple
beneath, rather thickly glandular, but either quite naked or hairy only
on the midrib and principal veins, the point narrowed out and acute,
the teeth sharp but neither very close nor deep, the lowest leaves
measuring about 1 inch across by 3 or 4 inches long. Inflorescence
a panicled arrangement of spikes, of which the main one is 3 or 4
inches long by ⅜ inch wide, the lowest whorls sometimes ½ an inch from
each other and the lowest bracts leafy. Bracteoles linear-subulate,
equalling or exceeding the expanded flowers, smooth or slightly
ciliated. Pedicels about ¾ line long, purplish glandular, but never
hairy. Calyx also often purplish, the tube campanulato-cylindrical,
⅜ line long, the teeth lanceolate-subulate, equalling the tube, the
flower part of which is naked, but the teeth and often the upper
part clothed more or less densely with erecto-patent hairs. Corolla
reddish-purple, about twice as long as the calyx, naked both within and
without. Not smooth.
The plant varies slightly in the shape of its leaves, elongation of
spike and hairiness of calyx. The entire plant emits a most fragrant
odour when rubbed, and has a pungent aromatic taste.
=Production=—Spearmint is grown in kitchen gardens, and more largely in
market gardens. A few acres are under cultivation with it at Mitcham,
chiefly for the sake of the herb, which is sold mostly in a dried state.
The cultivation of spearmint is carried on in the United States in
precisely the same manner as that of peppermint, but on a much smaller
scale. Mr. H. G. Hotchkiss of Lyons, Wayne County, State of New York,
has informed us that his manufacture of the essential oil amounted in
1870 to 1162 lb. The plant he employs appears from the specimen with
which he has favoured us, to be identical with the spearmint of English
gardens, and is not the Curled Mint (_Mentha crispa_) of Germany.
[1757] Seemann’s _Journal of Botany_, Aug. 1865. p. 239. We borrow Mr.
Baker’s careful description of _Mentha viridis_.
[1758] Part 2. (1568) 54.
=Chemical Composition=—Spearmint yields an essential oil (_Oleum
Menthæ viridis_) in which reside the medicinal virtues of the plant.
Kane,[1759] who examined it, gives its sp. gr. as 0·914, and its
boiling point as 160° C. The oil yielded him a considerable amount
of stearoptene. Gladstone[1760] found spearmint oil to contain a
hydrocarbon almost identical with oil of turpentine in odour and other
physical properties, mixed with an oxidized oil to which is due the
peculiar smell of the plant. The latter oil boils at 225° C.; its sp.
gr. is 0·951, and it was found to be isomeric with carvol, C₁₀H₁₄O.
According to our experiments the oil, distilled from Curled Mint grown
in Germany, deviates the plane of polarization 37°·4 to the left when
examined in a column of 100 millimetres. We prepared from it the
crystallized compound (C₁₀H₁₄0)₂SH₂, and isolated from it the liquid
C₁₀H₁₄O, which differs from carvol (see Fructus Carui, page 306) by its
levogyrate power.[1761]
=Uses=—Spearmint is used in the form of essential oil and distilled
water, precisely in the same manner as peppermint In the United States
the oil is also employed by confectioners and the manufacturers of
perfumed soap.
=Substitutes=—Oil of spearmint is now rarely distilled in England, its
high cost[1762] causing it to be nearly unsaleable. The cheaper foreign
oil is offered in price-currents as of two kinds, namely _American_ and
_German_. Of the first we have already spoken: the second, termed in
German _Krauseminzöl_, is the produce of _Mentha aquatica_ L. var. γ
_crispa_ Bentham, a plant cultivated in Northern Germany. Its oil seems
to agree with the oil of spearmint.