HOP (Ger. Hopfen, Fr. houblon), Humulus Lupulus, L., an herbaceous twining plant, belonging to the natural order Cannabinaceae, which is by some botanists included in the larger group called Urticaceae by Endlicher. It is of common occurrence in hedges and thickets in the southern counties of England, but is believed not to be native in Scotland. On the European continent it is distributed from Greece to Scandinavia, and extends through the Caucasus and Central Asia to the Altai Mountains. It is common, but doubtfully indigenous, in the northern and western states of North America, and has been introduced into Brazil, Australia and the Himalayas.
It is a perennial plant, producing annually several long twining roughish striated stems, which twist from left to right, are often 15 to 20 ft. long and climb freely over hedges and bushes. The roughness of stem and leaves is due to lines of strong hooked hairs, which help the plant to cling to its support. The leaves are stalked, opposite, 3-5 lobed, and coarsely serrate, and bear a general resemblance to those of the vine, but are, as well as the whole plant, rough to the touch; the upper leaves are sometimes scarcely divided, or quite entire. The stipules are between the leaf-stalks, each consisting of two lateral ones united, or rarely with the tips free. The male and female flowers are produced on distinct plants. The male inflorescence (fig. i, A) forms a panicle; the flowers consist of a small greenish five-parted perianth (a) enclosing five stamens, whose anthers (b) open by terminal slits. The female inflorescence (fig. i, B) is less conspicuous in the young state. The catkin or strobile consists of a number of small acute bracts, with two sessile ovaries at their base, each subtended by a rounded bractlet (c). Both the bracts and bractlets enlarge greatly during the development of the ovary, and form, when fully grown, the membranous scales of the strobile (fig. 2, a); they are known as " petals " by hop-growers. The bracts can then only be distinguished from the bractlets by being rather more acute and more strongly veined. The FIG. i. Male (A) and Female (B) Inflorescence of the Hop.
perianth (fig. i,d) is short, cup-shaped, undivided and closely applied to the ovary, which it ultimately encloses. In the young strobile the two purple hairy styles (e) of each ovary project beyond the bracts. The ovary contains a single ovule (fig. i.f) which -becomes in the fruit an exalbuminous seed, containing a spirally-coiled embryo (fig. 2, b). The light dusty pollen is carried by the wind from the male to the female flowers.
The ovary and the base of the bracts are covered with a yellowish powder, consisting of minute sessile grains, called lupulin or lupulinic glands. These glands (fig. 2, c) are from f Jir to xir i n - m diameter, like flattened subovate little saucers in shape, and attached to a short pedicel. The upper or hemispherical portion bears a delicate continuous membrane, the cuticle, which becomes raised by the secretion beneath it of the yellowish lupulin. The stalk is not perceptible in the gland as found in commerce. When fresh the gland is seen to be filled with a yellowish or dark brown liquid; this on drying contracts in bulk and forms a central mass. It is to these lupulinic glands that the medicinal properties of the hop are chiefly due. By careful sifting about i oz. may be obtained from i Ib of hops, but the East Kent variety is said to yield more than the Sussex hops.
In hop gardens a few male plants, usually three or four to an acre, are sometimes planted, that number being deemed sufficient to fertilize the female flowers. The blossoms are produced in August, and the strobiles are fit for gathering from the beginning of September to the middle of October, according to the weather.
The cultivation of hops for use in the manufacture of beer dates from an early period. In the 8th and pth centuries hop gardens, called " humularia " or " humuleta," existed in France and Germany. Until the 16th century, however, hops appear to have been grown in a very fitful manner, and to a limited extent, generally only for private consumption; but after the beginning of the 17th century the cultivation increased rapidly. The plant was introduced into England from Flanders in 1525; and in America its cultivation was encouraged by legislative enactments in 1657. Formerly several plants were used as well as hops to season ale, hence the name " alehoof " for Nepeta Glechoma, and " alecost " for Balsamila vulgaris. The sweet gale, Myrica Gale, and the sage, Salvia officinalis, FIG. 2. Fruit of Hop.
were also similarly employed. Various hop substitutes, in the form of powder, have been offered in commerce of late years, most of which appear to have quassia as a chief ingredient. The young tender tops of the hop are in Belgium cut off in spring and eaten like asparagus, and are forced from December to February.
Medical Use. The principal constituents of the strobiles are lupulin, one of the few liquid alkaloids; lupulinic acid, a bitter crystalline body, soluble in ether, which is without any other pharmacological action than that common to bitter substances; Valerol, a volatile oil which in old hops undergoes a change to the malodorous body valerianic acid; resin; trimethylamine; a peculiar modification of tannin known as humulotannic acid; and a sesqui-terpene. The British pharmacopoeia contains two preparations of the strobiles, an infusion (dose, 1-2 oz.) and a tincture (dose, j-l drachm). The glands obtained from the strobiles are known in pharmacy as lupulin, a name which tends to confusion with that of the alkaloid. They occur in commerce as a bright yellow-brown powder, seen under a lens to consist of minute glandular particles. The dose of this socalled lupulin is 2-5 grains. From it there is prepared the Tinctura Lupulinae of the United States pharmacopoeia, which is given in doses of 10-60 minims. Furthermore, there are prepared hop pillows, designed to procure sleep; but these act, when at all, mainly by suggestion. The pharmacological action of hops is determined first by the volatile oil they contain, which has the actions of its class. Similarly the lupulinic acid may act as a bitter tonic. The preparations of hops, when taken internally, are frequently hypnotic, though unfortunately different specimens vary considerably in composition, none of the preparations being standardized. It is by no means certain whether the hypnotic action of hops is due to the alkaloid lupulin or possibly to the volatile oil which they contain. Medical practice, however, is acquainted with many more trustworthy and equally safe hypnotics. The bitter acid of hops may endow beer containing it with a certain value in cases of impaired gastric digestion, and to the hypnotic principle of hops may partly be ascribed as well as to the alcohol the soporific action of beer in the case of some individuals.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)