HEMP, an annual herb (Cannabis sativa) having angular rough stems and deeply lobed leaves. The bast fibres of Cannabis are the hemp of commerce, but the products from many totally different plants are often included under the general name of hemp. In some cases the fibre is obtained from the stem, while in others it comes from the leaf. Sunn, Manila and Sisal hemps and Phormium (New Zealand flax, which is neither flax nor hemp) are treated separately. All these are often classed as hemp, and so are the following :—Ambari or Deccan hemp, Hibiscus cannabinus, an Indian and East Indian malvaceous plant, the fibre from which is often known as brown or Bombay hemp; Piteira or Mauritius hemp, which is obtained from Aloe creole, Furcraea foetida wille metiana, native in Brazil and cultivated in Mauritius; Agave americana; and Moorva or bowstring hemp, which is obtained from an aloe-like plant, Sansevieria zeylanica, and is a native of India and Ceylon.
Characteristics.—The hemp plant, like the hop, which is of the same family, Moraceae, is dioecious, i.e., the male and female flowers are borne on separate plants. The loose panicles of small yellow male flowers and the short spikes of green female flowers are borne in the axils of leaves at the top, or in clusters along the branches. The female flowers open only enough for the small feathery stigmas to protrude. Both male and female plants look alike until the time of flowering, after which the leaves on the male plants turn yellow and these plants die, while the female plants remain dark green about a month longer, or until the seeds ripen.
The plants have straight, erect, undivided stalks 3 to 18 feet high, generally about 5 to 8 feet when grown broadcast for fibre production. If not crowded or if planted in checks, as hemp is often cultivated for seed production, ascending leafy branches develop from nearly every node, but when sown broadcast for fibre production the crowded slender stalks are without branches or leaves except small tufts at the top.
Wild hemp still grows on the lower Ural, and the Volga, near the Caspian sea. It extends to Persia, the Altai range and north ern and western China. "It is found in Kashmir and in the Himalaya, growing so to 12 ft. high, and thriving vigorously at an elevation of 6,000 to i o,000 f t." (Plcarmacographia.) Wild hemp is little used for fibre but it produces a drug.
Origin and Distribution.—Hemp originated in some part of temperate Asia. The Emperor Shen Nung, in the twenty eighth century B.C., taught the people of China to cultivate "ma," a plant, male and female, for fibre. According to Herodotus the Thracians and Scythians beyond the Caspian Sea used hemp; but it seems to have been unknown in western Europe until the beginning of the Christian era. Hemp was grown in France in the middle ages, primarily for the seeds which were used for food.
Hemp is now cultivated for fibre production in Russia, Italy, Jugoslavia, Rumania, Hungary. Poland, Spain, Belgium, France, Turkey, China, Japan, the United States and Chile. Other forms are cultivated for the narcotic drug cannabin, known in different forms and in different countries as hasheesh, bhang, gunga, char ras, kif and marijuana, in India, Arabia, Africa and Mexico. In China, Manchuria and in some parts of Russia short stalked varieties of hemp are now cultivated for seed, which produces oil similar to linseed oil.
Although different forms have been described under different botanical names there are no essential differences in any of the specific characters and all cultivated and wild hemp is now recog nized as belonging to one species, Cannabis sativa L.
Cultivation.—Hemp is an annual crop. The seed is sown as early in the spring as the land can be well prepared. The seed weighs 44 pounds per bushel and it is sown at the rate of 33 to 66 pounds per acre, the higher rate being sown on more fertile soils. The seed is sown broadcast by hand, or better with a drill, and the field is usually rolled after the seed is covered. In some places in Europe the fields are weeded by hand after the hemp is up, but if the land is well prepared and the seed sown early the dense growth of hemp will usually kill out all weeds that may start later. The crop is harvested when the staminate plants are in flower, about four months after seeding. In Europe and in China and Japan, it is usually cut by hand with a straight bladed sickle. In many fields the largest female plants are left to produce seed. After cutting, the stalks,-3 to 8 ft. long and about the thickness of a pencil,—are laid flat on the ground for 2 or 3 days, then set up in shocks for about a week. In the United States the crop is cut with self-rake reaping machines, or more often with large hemp harvesters which cut a swath 71 ft. wide and lay the stalks smoothly and evenly on the ground where they remain until retted, requiring 3 to 6 weeks. The retted stalks are then picked up by another large machine which binds them in bundles. The bundles are set up in shocks to dry, after which they are hauled to the scutching mills and stored in sheds to await scutching. Hemp seed for sowing is there produced on plants grown in checks and cultivated like maize. This produces better seeds than are available from crowded plants grown broadcast for fibre production.
Preparation of Fibre.—In Italy and to some extent in other European countries, the hemp stalks, after curing in the shock, are tied in bundles and retted in water. They are left in the water from so to 20 days, or until the bark, including the fibre, sepa rates easily from the woody, inner portion of the stalk. Some of the hemp in Italy, and much of it in other countries, is dew retted by spreading it on the ground where it is exposed to dew and rain. This method of retting requires 15 to 3o days, but it is the least expensive, for there is usually no cost except the work of spread ing the stalks and picking them up. The hemp stalks, either dew retted, or water-retted are set up in loose open shocks to dry. The fibre is separated from the dry stalks by means of hand brakes, or in northern Italy by power driven machines. In these machines handfuls of retted stalks pass endwise between rapidly revolving, fluted rollers, which break the woody portion into small pieces called hurds. The fibre is then held by hand so that the loosened hurds are beaten away by smooth projections on revolv ing cylinders. The Italian hemp is very carefully graded before being baled for shipment. In China and Japan some of the hemp fibre is prepared by steaming the stalks and stripping off the fibre by hand.
In the United States the work of scutching is done in winter, inside of buildings where it is independent of weather conditions. The retted stalks that have been stored in stacks or sheds, pass through long driers, then endwise through several pairs of fluted rollers, after which the fibre is turned sidewise and grasped near the centre by belts that take it past three pairs of scutching drums. The tow beaten out in scutching the long fibre and also that produced from short or tangled stalks, is cleaned by a tow machine. The hurds, used as fuel, furnish steam for the drier and for operating all of the machinery of the scutching mill.
Hemp Fibre.—Hemp is a soft fibre or bast fibre. It consists of very narrow flat strands from 3 to so ft. long. The ultimate cells composing these strands area to i - in. long. Dew retted hemp is gray; Italian water-retted, light yellow or golden yellow; and Russian water-retted, usually greenish. Hemp is the strongest and most durable of any of the commercial soft fibres except flax. It is more nearly like flax than any other fibre, and the finest hemp is often used as a substitute for the coarser grades of flax. For more than 20 centuries hemp was the principal fibre used in ropes, but abaci (Manila hemp), stronger and lighter, has taken its place in marine cordage and in most other ropes, while jute, cheaper and more easily spun, but weaker and much less durable, has taken its place in sacking cloth, twines and for many purposes where hemp with its greater strength and durability would give better service.
Hemp is used in the manufacture of strong tying twines, sack ing twine, book binders' twine, shoe and harness thread, net twine, carpet warp, marlines, canvas, sails, and in Europe it is used extensively in ropes of superior quality. Hemp tow is used in tarred oakum and in packing for pumps and engines.
The drug has no external action. The apparent impossibility of obtaining it in pure and trustworthy form has led to its entire abandonment in therapeutics. When a good sample is obtained it is a safe and efficient hypnotic, at any rate in the case of a Euro pean. The tincture should not be prescribed unless precautions are taken to avoid the precipitation of the resin which follows its dilution with water.
See Watt, Dictionary of the Economic Products of India.