Lactuca scariola Linn.
Local
names: Lechuga (Sp.); lettuce (Engl.); letsugas (Tag.).
Lechugas
is commonly cultivated in gardens for food, but is nowhere established.
This vegetable is an erect, usually simple, annual, smooth, very leafy herb reaching a height of 1 meter when in flower. The leaves are stalkless, obovate to oblong-obovate, 6 to 20 centimeters long, entire or lobed, toothed, thin, and numerous at the base. The heads are numerous, about 1 centimeter long, and borne in open panicles; the branches (often much reduced) bear bractlike leaves. The flowers are yellow. The involucral bracts are ovate, the inner ones linear. The achenes are brown, with a very slender beak about as long as the body.
According
to Marañon the green leaves are excellent sources of calcium, phosphorus, and
iron. Hermano says that lettuce is an excellent source of vitamins A and C and
a good source of vitamin B.
Wehmer
records that the leaves contain a bitter principle, lactucin; mannite; and
malic acid; asparagin; and oxalic acid. The whole plant, in addition, contains
volatile oil, vitamin A, and a trace of hyoscyamine. The latex contains d- and B-lectucerol, inosite, reducing sugar, and a bitter principle.
According
to Pareira the early leaves of lettuce, eaten as a salad are easily digested,
but they yield only a small portion of nutritive matter. They probably possess,
in a very mild degree, soporific properties. The ancients considered them
antiaphrodisiac. The flowering plant is more powerful and produces, in a feeble
degree, the effects of lacturacium. Lettuce also possesses slight hypnotic
properties. It may be taken with advantage at supper to promote sleep.
(Lactucarium, or lettuce opium, mentioned in the old pharmacopoeias, is the
concrete, milky juice of the plant.) Dymock considers lettuce to possess
cooling and refreshing properties.
The plant
is official in the Belgian (1,2); French (1-4); Mexican (1-4); Portuguese
(2,3); Rumanian (1,2); Serbian (1); Spanish (2-7); Swiss (2); and Venezuelan
91,2) Pharmacopoeias.
Kirtikar
and Basu quote Dr. Duncan, who showed that the juice might be used as a
substitute for opium. They report that the extract from the fresh plant is a
mild sedative and is anodyne, purgative, diuretic, diaphoretic, and
antispasmodic; it is also said to be useful in the treatment of coughs in
phthisis, bronchitis, asthma, and pertussis. A lettuce poultice is a soothing
application to painful and irritable ulcers.
Hooper says that the seeds are slightly aromatic and have a bitter taste. An infusion of the seeds is given in fevers – typhoid in particular. Honigberger states that lettuce seeds are given in excessive thirst and also for a sensation of heat in the stomach. It is supposed that, by relaxing the genital organs, they diminish the spermatic secretion. Watt reports that a decoction of the seeds is used as a demulcent. The seeds are given boiled or made into confection in cases of bronchitis, especially the chronic type.