_Lemon_; F. _Citron_, _Limon_; G. _Citrone_, _Limone_.
=Botanical Origin=—_Citrus Limonum_ Risso (_C. Medica_ var. β Linn.), a
small tree 10 to 15 feet in height, planted here and there in gardens
in many subtropical countries, but cultivated as an object of industry
on the Mediterranean coast between Nice and Genoa, in Calabria, Sicily,
Spain, and Portugal.
The tree which is supposed to represent the wild state of the lemon and
lime, and as it seems to us after the examination of numerous specimens
in the herbarium of Kew, of the citron (_Citrus Medica_ Risso) also,
is a native of the forests of Northern India, where it occurs in the
valleys of Kumaon and Sikkim.
The cultivated lemon-tree is of rather irregular growth, with foliage
somewhat pallid, sparse, and uneven, not forming the fine, close head
of deep green that is so striking in the orange tree. The young shoots
are of a dull purple; the flowers, which are produced all the year
except during the winter, and are in part hermaphrodite and in part
unisexual, have the corolla externally purplish; internally white, and
a delicate aroma distinct from that of orange blossom. The fruit is
pale yellow, ovoid, usually crowned by a nipple.
[451] Already known to Piso.
[452] The original Jaborandi of Piso, according to Peckolt.
Dragendorff’s _Jahresbericht_, 1875. 163.
=History=—The name of the lemon in Sanskrit is _Nimbuka_; in
Hindustani, _Limbu_, _Limu_, or _Ninbu_. It is probably originally a
Cashmere word, which was transferred to the Sanskrit in comparatively
modern times, not in the antiquity.[453] From these sounds the Arabians
formed the word _Limun_, which has passed into the languages of Europe.
The lemon was unknown to the inhabitants of ancient Greece and Rome;
but it is mentioned in the Book of Nabathæan Agriculture,[454] which
is supposed to date from the 3rd or 4th century of our era. The
introduction of the tree to Europe is due to the Arabians, yet at
what precise period is somewhat doubtful. _Arance_ and _Limone_ are
mentioned by an Arabic poet living in the 11th century, in Sicily,
quoted by Falcando.[455] The geographer Edrisi,[456] who resided at the
court of Roger II., king of Sicily, in the middle of the 12th century,
mentions the lemon (_limouna_) as a very sour fruit of the size of an
apple which was one of the productions of Mansouria on the Mahrân or
Indus; and he speaks of it in a manner that leads one to infer it was
not then known in Europe. This is the more probable from the fact that
there is no mention either of lemon or orange in a letter written A.D.
1239 concerning the cultivation of the lands of the Emperor Frederick
II. at Palermo,[457] a locality in which these fruits are now produced
in large quantity.
On the other hand the lemon is noticed at great length by Ibn Baytar
of Malaga, who flourished in the first half of the 13th century,
but of its cultivation in Spain at that period there is no actual
mention.[458] In 1369 at least citron trees, “arbores citronorum,”
were planted in Genoa,[459] and there is evidence that also the
lemon-tree was grown on the Riviera di Ponente about the middle of the
15th century, since _Limones_ and also _Citri_ are mentioned in the
manuscript _Livre d’Administration_ of the city of Savona, under date
1486.[460] The lemon was cultivated as early as 1494 in the Azores,
whence the fruit used to be largely shipped to England; but since the
year 1838 the exportation has totally ceased.[461]
=Description=—The fruit of _Citrus Limonum_ as found in the shops[462]
is from about 2 to 4 inches in length, egg-shaped with a nipple more
or less prominent at the apex; its surface, of a pale yellow, is even
or rugged, covered with a polished epidermis. The parenchyme within
the latter abounds in large cells filled with fragrant essential oil.
The roughness of the surface of the rind is due to the oil-cells. The
peel, which varies considerably in thickness but is never so thick as
that of the citron, is internally white and fibrous, and is adherent
to the pale yellow pulp. The latter is divided into 10 or 12 segments
each containing 2 or 3 seeds. It abounds in a pale yellow acid juice
having a pleasant sour taste and a slight peculiar odour quite distinct
from that of the peel. When removed from the pulp by pressure, the
juice appears as a rather turbid yellowish fluid having a sp. gr. which
varies from 1·040 to 1·045, and containing in each fluid ounce from 40
to 46 grains of citric acid, or about 9½ per cent.[463] In Italy all
the fine and perfect fruit is exported; the windfalls and the damaged
fruit are used for the production of the essential oil and the juice.
About 13,000 lemons of this kind yield one pipe (108 gallons) of raw
juice. Sicilian juice in November will contain about 9 ounces of citric
acid per gallon, but 6 ounces when afforded by the fruit collected in
April. The juice is boiled down in copper vessels, over an open fire,
till its specific gravity is about 1·239.[464] Lemon juice (_Succus
limonis_) for administration as a medicine should be pressed as wanted
from the recent fruit whenever the latter is obtainable.
[453] Dr. Rice in _New Remedies_, 1878, 263; also private information.
[454] Meyer, _Geschichte der Botanik_, iii. (1856) 68.
[455] Amari, _Storia dei Musulmani di Sicilia_, ii. (1858) 444.
[456] _Géographie d’Edrisi_, traduite par Jaubert, i. (1836) 162.
[457] Huillard-Bréholles, _Historia diplomatica Friderici secundi_,
Paris, v. (1857) 571.
[458] _Heil-und Nahrungsmittel von Ebn Baithar_, übersetzt von
Sontheimer, ii. (1842) 452.
[459] Belgrano, _Vita privata dei Genovesi_, Genova (1875) 158.
[460] Gallesio, _Traité du Citrus_ (1811) 89, 103.
[461] Consul Smallwood, in _Consular Reports_, Aug. 1873. 986.
[462] There are many kinds of lemon as well as of orange which are
never seen in commerce. Risso and Poiteau enumerate 25 varieties of
the former and 30 of the latter. See also Alfonso, _Coltivazione degli
Agrumi_, Palermo, 2nd edition, 1875.
[463] Stoddart, in _Pharm. Journ._ x. (1869) 203.
[464] R. Warington, _Pharm. Journ_. v. (1875) 385.
The peel (_Cortex limonis_) cut in somewhat thin ribbons from the fresh
fruit is used in pharmacy, and is far preferable to that sold in a
dried state.
=Microscopic Structure of the Peel.=—The epidermis exhibits numerous
stomata; the parenchyme of the pericarp encloses large oil-cells,
surrounded by small tabular cells. The inner spongy tissue is built up
of very remarkable branched cells, separated by large intercellular
spaces. A solution of iodine in iodide of potassium imparts to the
cell-walls a transient blue coloration. The outer layers of the
parenchymatous tissue contain numerous yellowish lumps of a substance
which assumes a brownish hue by iodine, and yields a yellow solution
if potash be added. Alkaline tartrate of copper is reduced by this
substance, which probably consists of hesperidin. There also occur
large crystals of oxalate of calcium, belonging to the monoclinic
system. The interior tissue is irregularly traversed by small vascular
bundles.
=Chemical Composition=—The peel of the lemon abounds in essential
oil, which is a distinct article of commerce, and will be described
hereafter.
Lemons, as well as other fruits of the genus _Citrus_, contain a bitter
principle, _Hesperidin_, of which E. Hoffmann[465] obtained 5 to 8
per cent. from unripe bitter oranges. He extracted them with dilute
alcohol, after they had previously been exhausted by cold water. The
alcohol should contain about 1 per cent. of caustic potash; the liquid
on cooling is acidulated with hydrochloric acid, when it yields a
yellowish crystalline deposit of hesperidin, which may be obtained
colourless and tasteless by recrystallization from boiling alcohol. By
dilute sulphuric acid (1 per cent.) hesperidin is broken up as follows:—
C₂₂H₂₆O₁₂ = C₁₆H₁₄O₆ + C₆H₁₂O₆.
Hesperidin. Hesperetin. Glucose.
Hesperidin is very little soluble even in boiling water or in ether,
but dissolves readily in hot acetic acid, also in alkaline solutions,
the latter then turning soon yellow and reddish. Pure hesperidin, as
presented to one of us by Hoffmann, darkens when it is shaken with
alcoholic perchloride of iron, and turns dingy blackish brown when
gently warmed with the latter.
[465] _Berichte der Deutschen Chemischen Gesellschaft_ (1876) 26, 685,
693.
_Hesperetin_ forms crystals melting at 223° C., soluble both in alcohol
or ether, not in water; they taste sweet. They are split up by potash
in Phloroglucin and _Hesperetic acid_, C₁₀H₁₀O₄.
On addition of ferric chloride, thin slices of the peel are darkened,
owing probably to some derivative of hesperidin, or to hesperidin
itself.
The name hesperidin had also been applied to _yellow_ crystals
extracted from the shaddock, _Citrus decumana_ L., the dried flowers
of which afford about 2 per cent. of that substance. It is, as
shown in 1879 by E. Hoffmann, quite different from hesperidin as
described above; he calls it _Naringin_ and assigns to it the formula
C₂₃H₂₆O₁₂+4OH₂. Naringin is readily soluble in hot water or in alcohol,
not in ether or chloroform. Its solutions turn brown-red on addition of
ferric chloride.
Lemon juice, some of the characters of which have been already noticed,
is an important article in a dietetic point of view, being largely
consumed on shipboard for the prevention of scurvy. In addition to
citric acid it contains 3 to 4 per cent. of gum and sugar, and 2·28 per
cent. of inorganic salts, of which according to Stoddart only a minute
proportion is potash. Cossa[466] on the other hand, who has recently
studied the products of the lemon tree with much care, has found that
the ash of dried lemon juice contains 54 per cent. of potash, besides
15 per cent. of phosphoric acid.
Stoddart has pointed out the remarkable tendency of citric acid to
undergo decomposition,[467] and has proved that in lemons kept from
February to July this acid generally decreases in quantity, at first
slowly, but afterwards rapidly, until at the end of the period it
entirely ceases to exist, having been all split up into glucose and
carbonic acid. At the same time the sp. gr. of the juice was found to
have undergone but slight diminution:—thus it was 1·044 in February,
1·041 in May, and 1·027 in July, and the fruit had hardly altered in
appearance. Lemon juice may with some precautions be kept unimpaired
for months or even years. Yet it is capable of undergoing fermentation
by reason of the sugar, gum, and albuminoid matters which it contains.
=Commerce=—Lemons are chiefly imported from Sicily, to a smaller extent
from the Riviera of Genoa and from Spain. From the published statistics
of trade, in which lemons are classed together with oranges under one
head, it appears that these fruits are being imported in increasing
quantities. The value of the shipments to the United Kingdom in 1872
(largely exceeding those of any previous year) was £1,154,270. Of this
sum, £986,796 represents the value of the oranges and lemons imported
from Spain, Portugal, the Canary Islands and Azores; £155,330 the
shipments of the same fruit from Italy; and £3,825 those from Malta.
Of concentrated _lemon juice_ there were exported in 1877 from
Messina 1,631,332 kilogrammes, valued at 2,446,996 lire. The value of
concentrated _lime juice_ exported in 1874 from Montserrat was £3,390.
From Dominica, 11,285 gallons, value £1,825, were shipped in 1875.
[466] _Gazetta Chimica Italiana_, ii. (1872) 385; _Journ. of Chem.
Soc._ xi (1873) 402.
[467] Stoddart’s statement that if potash be added to lemon juice,
_oxalic acid_ may be detected in the mixture after a few days, is not
supported by our observations.
=Uses=—Lemon peel is used in medicine solely as a flavouring
ingredient. Freshly prepared lemon juice is often administered with an
alkaline bicarbonate in the form of an effervescing draught, or in a
free state.
Concentrated _lemon juice_ is imported for the purpose of making citric
acid; it is derived not only from the lemon, but also, to a smaller
extent, from the lime and bergamot. _Lime juice_ of the West Indies is
chiefly used as a beverage; small quantities of it are also exported
for the manufacture of citric acid. The culture of _Citrus Limetta_
Risso, the _lime_, was introduced in Montserrat in 1852.