(part 1 of 6)

YEARBOOK OF THE UNITED STATES DEPARTMENT OF AGRICULTURE--1913

HEMP

By Lyster H. Dewey--Botanist in Charge of Fiber Plant Investigations,
Bureau of Plant Industry.

INTRODUCTION

The two fiber-producing plants most promising for cultivation in
the central United States and most certain to yield satisfactory profits
are hemp and flax. The oldest cultivated fiber plant, one for which the
conditions in the United States are as favorable as anywhere in the world,
one which properly handled improves the land, and which yields one of the
strongest and most durable fibers of commerce, is hemp. Hemp fiber,
formerly the most important material in homespun fabrics, is now most
familiar to the purchasing public in this country in the strong gray tying
twines one-sixteenth to one-fourth inch in diameter, known by the trade
name "commercial twines."

NAME.

The name "hemp" belongs primarily to the plant Cannabis sativa.
(pl. XL, fig.1.) It has long been used to designate also the long fiber
obtained from the hemp plant. (Pl. XL, fig. 4.) Hemp fiber, being one of
the earliest and best-known textile fibers and until recent times the most
widely used of its class, has been regarded as the typical representative
of long fibers. Unfortunately, its name also came to be regarded as a kind
of common name for all long fibers, until one now finds in the market
quotations "Manila hemp" for abaca, "sisal hemp" for sisal and henequen,
"Mauritius hemp" for Furcraea fiber, "New Zealand hemp" for phormium, "Sunn
hemp" for Crotalaria fiber, and "India hemp" for jute. All of these fibers
in appearance and in economic properties are unlike true hemp, while the
name is never applied to flax, which is more nearly like hemp than any
other commercial fiber.

The true hemp is known in different languages by the following
names: Cannabis, Latin; chanvre, French; canamo, Spanish; canhamo,
Portuguese; canapa, Italian; canep, Albanian; konopli, Russian; konopj
and penek, Polish; kemp, Belgian; hanf, German; hennep, Dutch; hamp,
Swedish; hampa, Danish; kenevir, Bulgarian; ta-ma, si-ma, and tse-ma,
Chinese; asa, Japanese; nasha, Turkish; kanabira, Syrian; kannab,
Arabic.

IMPORTANCE OF HEMP.

Hemp was formerly the most important long fiber, and it is now used
more extensively than any other soft fiber except jute. From 10,000 to
15,000 tons are used in the United States every year. The approximate
amount consumed in American spinning mills is indicated by the following
table, showing the average annual importations (-Computed from reports of
the Bureau of Navigation and Commerce, U.S. Treasury Department Bureau of
Statistics Department of Commerce) and estimates of average domestic
production of hemp fiber for 35 years:

Average annual imports and estimates of average annual production of hemp
fiber in 5-year periods from 1876 to 1910, inclusive, and from 1911 to
1913, inclusive.
(Place chart here from p. 284)

There are no statistics available, such as may be found for wheat,
corn, or cotton, showing with certainty the acreage and production of hemp
in this country. The estimates of production in the foregoing table are
based on the returns of the Commissioner of Agriculture of Kentucky for
earlier years with amounts added to cover the production in other States,
and on estimates of hemp dealers for more recent years. While these
figures can not be regarded as accurate statistics, and they are probably
below rather than above the actual production, especially in the earlier
years, they indicate a condition well recognized by all connected with the
industry. The consumption of hemp fiber has a slight tendency to increase,
but the increase is made up through increased importations, while the
domestic production shows a tendency toward reduction.

PRODUCTION IN THE UNITED STATES DECLINING.

This falling off in domestic production has been due primarily to
the increasing difficulty in securing sufficient labor to take care of the
crop; secondarily, to the lack of development of labor-saving machinery as
compared with the machinery for handling other crops and to the increasing
profits in raising stock, tobacco, and corn, which have largely taken the
attention of farmers in hemp-growing regions.
The work of retting, breaking, and preparing the fiber for market
requires a special knowledge, different from that for handling grain crops,
and a skill best acquired by experience. These factors have been more
important than all others in restricting the industry to the bluegrass
region of Kentucky, where the plantation owners as well as the farm
laborers are familiar with every step in handling the crop and producing
the fiber.

An important factor, tending to restrict the use of hemp, has been
the rapidly increasing use of other fibers, especially jute, in the
manufacture of materials formerly made of hemp. Factory-made woven goods
of cotton or wool, more easily spun by machinery, have replaced the hempen
"homespun" for clothing; wire ropes, stronger, lighter, and more rigid,
have taken its place in standing rigging for ships; abaca (Manila hemp),
lighter and more durable in salt water; has superseded it for towing
hawsers and hoisting ropes; while jute, inferior in strength and
durability, and with only the element of cheapness in its favor, is
usurping the legitimate place of hemp in carpet warps, so-called "hemp
carpets," twines, and for many purposes where the strength and durability
of hemp are desired.
The introduction of machinery for harvesting hemp and also for
preparing the fiber, together with the higher prices paid for hemp during
the past three years, has aroused an interest in the industry, and many
experiments are being tried with a view to the cultivation of the crop in
new areas.

BOTANICAL STUDY OF HEMP

THE PLANT.

The hemp plant, Cannabis sativa L., (Linnaeus. Species Plantarum,
ed. 1,1027, 1753. Dioscorides. Medica Materia, libri sex, p. 147, 1537.
Synonyms: Cannabis erratica paludesa Anders. Lobel. Stirpium Historia,
184, 1576.
Cannabis indica Lamarck. Encyclopedia, 1: 695, 1788.
Cannabis macrosperma Stokes. Bot. Mat. Med., IV, 539, 1812.
Cannabis chinensis Delile. Ind. Sem. Hort. Monst. in Ann. Sci.
Nat. Bot., 12: 365, 1849.
Cannabis gigantea Delile. L. Vilmorin. Rev. Hort., 5: s. 3, 109,
1851.)

is an annual, growing each year from the seed. It has a rigid, herbaceous
stalk, attaining a height of 1 to 5 meters (3 to 16 feet), obtusely
4-cornered, more or less fluted or channeled, and with well-marked nodes at
intervals of 10 to 50 centimeters (4 to 20 inches). When not crowded it
has numerous spreading branches, and the central stalk attains a thickness
of 3 to 6 centimeters (1 to 2 inches), with a rough bark near the base. If
crowded, as when sown broadcast for fiber, the stalks are without branches
or foliage except at the top, and the smooth fluted stems are 6 to 20
millimeters (1/4 to 3/4 inch) in diameter. The leaves, opposite, except
near the top or on the shortened branches, appearing fascicled, are
palmately compound and composed of 5 to 11--usually 7--leaflets. (Pl. XLI,
fig. 1). The leaflets are dark green, lighter below, lanceolate, pointed
at both ends, serrate, 5 to 15 centimeters (2 to 6 inches) long, and 1 to 2
centimeters (3/8 to 3/4 inch) wide. Hemp is dioecious, the staminate or
pollen-bearing flowers and the pistillate or seed-producing flowers being
borne on separate plants. The staminate flowers (Pl. XL, fig. 2) are
borne in small axillary panicles, and consist of five greenish yellow or
purplish sepals opening wide at maturity and disclosing five stamens which
discharge abundant yellow pollen. The pistillate flowers (Pl. XL, fig. 3)
are stemless and solitary in the axils of the small leaves near the ends
of the branches, often crowded so as to appear like a thick spike. The
pistillate flower is inconspicuous, consisting of a thin, entire, green
calyx, pointed, with a slit at one side, but remaining nearly closed over
the ovary and merely permitting the two small stigmas to protrude at the
apex. The ovary is one seed, developing into a smooth, compressed or
nearly spherical achene (the "seed"), 2.5 to 4 millimeters (1/10 to 3/16
inch) thick and 3 to 6 millimeters (1/8 to 1/4 inch) long, from dark gray
to light brown in color and mottled (Pl. XLI, fig. 2). The seeds cleaned
for market nearly always include some still covered with the green, gummy
calyx. The seeds vary in weight from 0.008 to 0.027 gram, the dark-colored
seeds being generally much heavier than the light-colored seeds of the same
sample. The light-colored seeds are often imperfectly developed.
Dark-colored and distinctly mottled seeds are generally preferred.
The staminate plants are often called the flowering hemp, since the
pistillate flowers are rarely observed. The staminate plants die after the
pollen is shed, but the pistillate plants remain alive and green two months
later, or until the seeds are fully developed.

THE STALK

The hemp stalk is hollow, and in the best fiber-producing types the
hollow space occupies at least one-half the diameter. The hollow space is
widest, or the surrounding shell thinnest, about midway between the base
and the top of the plant. The woody shell is thickened at each node,
dividing the hollow space into a series of partly separated compartments.
(Pl. XLI, fig. 4.) If the stalk is cut crosswise a layer of pith, or
thin-walled tissue, is found next to the hollow center, and outside of this
a layer of wood composed of hard, thick-walled cells. This layer, which
forms the "hurds," is a very thin shell in the best fiber-producing
varieties. It extends clear across the stem below the lowest node, and in
large, coarse stalks grown in the open it is much thicker and the central
hollow relatively smaller. Outside of the hard woody portion is the soft
cambium, or growing tissue, the cells of which develop into the wood on the
inside, or into the bast and bark on the outside. It is chiefly through
this cambium layer that the fiber-bearing bast splits away from the wood in
the processes of retting and breaking. Outside of the cambium is the inner
bark, or bast, comprising short, thin-walled cells filled with chlorophyll,
giving it a green color, and long thick-walled cells, making the bast
fibers. These bast fibers are of two kinds, the smaller ones (secondary
bast fibers) toward the inner portion making up rather short, fine fibers,
many of which adhere to the wood or hurds when the hemp is broken, and the
coarser ones (primary bast fibers) toward the outer part, extending nearly
throughout the length of the stalk. Outside of the primary bast fiber is a
continuation of the thin-walled chlorophyll-bearing cells free from fiber,
and surrounding all is the thin epidermis.

THE FIBER.

The hemp fiber of commerce is composed of the primary bast fibers,
with some adherent bark and also some secondary bast fiber. The bast
fibers consist of numerous long, overlapping, thick-walled cells with long,
tapering ends. The individual cells, almost too small to be seen by the
unaided eye are 0.015 to 0.05 millimeter (3/1000 to 12/1000 inch ) in
diameter, and 5 to 55 millimeters (3/16 to 2 1/8 inches) long. Some of
the bast fibers extend through the length of the stalk, but some are
branched, and some terminate at each node. They are weakest at the nodes.

RELATIONSHIPS

The hemp plant belongs to the mulberry family, Moraceae, which
includes the mulberry, the Osage orange, the paper mulberry, from the bast
of which the tapa of the South Sea Islands is made, and the hop, which
contains a strong bast fiber. Hemp is closely related to the nettle
family, which includes ramie, an important fiber-producing plant of Asia
and several species of nettles having strong bast fibers.
The genus Cannabis is generally regarded by botanists as monotypic,
and the one species Cannabis sativa is now held to include the half dozen
forms which have been described under different names (see footnote, p.
286) and which are cultivated for different purposes. The foregoing
description refers especially to the forms cultivated for the production of
fiber.

HISTORY

EARLY CULTIVATION IN CHINA.

Hemp was probably the earliest plant cultivated for the production
of a textile fiber. The "Lu Shi," a Chinese work of the Sung dynasty,
about 500 A.D., contains a statement that the Emperor Shen Nung, in the
twenty-eighth century B.C., first taught the people of China to cultivate
"ma" (hemp) for making hempen cloth. The name ma (fig. 17) occurring in
the earliest Chinese writings designated a plant of two forms, male and
female, used primarily for fiber. Later the seeds of this plant were used
for food. (- Bretschneider, E. Botannicum Sinicum, in Journal of the
North China Branch of the Royal Asiatic Society, n.s., v. 25, p.203, 1893,
Shanghai.) The definite statement regarding the staminate and pistillate
forms eliminates other fiber plants included in later times under the
Chinese name ma. The Chinese have cultivated the plant for the production
of fiber and for the seeds, which were used for food and later for oil,
while in some places the stalks are used for fuel, but there seems to be no
record that they have used the plant for the production of the narcotic
drugs bhang, charas, and ganga. (sic)` The production and use of these
drugs were developed farther west.

CULTIVATION FOR NARCOTIC DRUGS.

The use of hemp in medicine and for the production of the narcotic
drug Indian hemp, or cannabis, is of interest in this paper only because of
its bearing on the origin and development of different forms of the plant.
The origin of this use is not definitely known, but the weight of evidence
seems to indicate central Asia or Persia and a date many centuries later
than its first cultivation for fiber. The name bhanga occurs in the
Sanskrit "Atharvaveda" (about 1400 B.C.), but the first mention of it as a
medicine seems to be in the work of Susruta (before the eighth century
A.D.), while in the tenth century A.D. its intoxicating nature seems to
have been known, and the name "indracana" (Indra's food) first appears in
literature. (Watt, Sir George. Commercial Products of India, p. 251,
1908.) A further evidence that hemp, for the production of fiber as well
as the drug, has been distributed from central Asia or Persia is found in
the common origin of the names used. The Sanskrit names "bhanga" and
"gangika," slightly modified to "bhang" and "ganja," are still applied to
the drugs, and the roots of these words, "and" and "an," recur in the names
of hemp in all of the Indo-European and modern Semitic languages, as bhang,
ganja, hanf, hamp, hemp, chanvre, canamo, kannab, cannabis. (De Candolle,
Alphonse. Origin of Cultivated Plants, p. 143, 1886)

HEMP IN INDIA

Northern India has been regarded by some writers as the home of the
hemp plant, but it seems to have been unknown in any form in India before
the eighth century, and it is now thought to have been introduced there
first as a fiber plant. It is still cultivated to a limited extent for
fiber in Kashmir and in the cool, moist valleys of the Himalayas, but in
the warmer plains regions it is grown almost exclusively for the production
of the drugs. (Watt, Sir George. Commercial Products of India, p. 253,
1908.)
Hemp was not known to the Hebrews nor to the ancient Egyptians, but
in medieval times it was introduced into North Africa, where it has been
cultivated only for the drug. It is known in Morocco as "kif," and a small
form, 1 to 3 feet high, cultivated there has been described as a distinct
variety, Cannabis sativa kif. (De Candolle, Alphonse. Prodromus, v. 16,
pt. 1, p.31,1869.)

INTRODUCTION INTO EUROPE.

According to Herodotus (about 450 B.C.), the Thracians and
Scythians, beyond the Caspian Sea, used hemp, and it is probable that the
Scythians introduced the plant into Europe in their westward migration,
about 1500 B.C., though it seems to have remained almost unknown to the
Greeks and Romans until the beginning of the Christian era. The earliest
definite record of hemp in Europe is the statement that "Hiero II, King of
Syracuse (270 B.C.), bought hemp in Gaul for the cordage of his vessels."
(De Candolle, Alphonse. Origin of Cultivated Plants, p. 148, 1886.) From
the records of Tragus (1539 A.D.), hemp in the sixteenth century had
become widely distributed in Europe. It was cultivated for fiber, and its
seeds were cooked with barley and other grains and eaten, though it was
found dangerous to eat too much or too frequently. Dioscorides called the
plant Cannabis sativa, a name it has continued to bear to the present time,
and he wrote of its use in "making the stoutest cords" and also of its
medicinal properties. ( (Dioscorides. Medica Materia, li bri sex, p.
147, 1537.) Nearly all of the early herbalists and botanical writers of
Europe mention hemp, but there is no record of any further introduction of
importance in the fiber industry until the last century.

INTRODUCTION OF CHINESE HEMP INTO EUROPE.

In 1846 M. Hebert sent from China to the Museum at Paris some seeds
of the "tsing-ma" great hemp, of China. Plants from this seed, grown at
Paris by M.L. Vilmorin, attained a height of more than 15 feet, but did not
produce seeds. In the same year M. Itier sent from China to M. Delile, of
the Garden at Montpellier, France, seeds of a similar kind of hemp. These
seeds were distributed in the southern part of France, where the plants not
only grew tall, some of them measuring 21 feet, but they also produced
mature seeds. M. Delile called this variety Cannabis chinensis (Delile,
Raffenau. Index seminum hortl botanici Monspeliensis. Ann. Sci. Nat. Bot.,
v. 12, p. 365, 1849.) and the one from the seeds sent by M. Hebert he
called C. gigantea. (Vilmorin, L. Chanvre de Chine. Rev. Hort. 5: s. 3,
p. 109, 1851) These two forms of hemp were regarded as the same by M.L.
Vilmorin, who states that they differ very much in habit from the common
hemp of Europe, which was shorter and less valuable for fiber production.
We are also told that this chanvre de Chine did not appear to be the same
as the chanvre de Piedmont, (5-footnote missing from transcription, p. 290)
the tall hemp of eastern France and northern Italy, the origin of which has
sometimes been referred to this introduction, but this may have originated
in a previous introduction, since Cannabis chinensis is mentioned as
having been in the Botanical Garden at Vienna in 1827. In the same
statement, however, C. sativa pedemontana is described as a distinct
variety. ( De Candolle, Alphonse. Prodromus, v. 16, pt. 1, p.31, 1869.)
Particular attention is called to the introduction of this large Chinese
hemp into Europe, since it was doubtless from the same source as the best
hemp seed now brought from China to the United States.

INTRODUCTION INTO SOUTH AMERICA.

Hemp from Spain was introduced into Chile about 1545. (Husbands,
Jose D. U.S. Department of Agriculture, Bureau of Plant Industry, Bulletin
153, p. 42, 1909.) It has been largely grown in that country, but at
present its cultivation is confined chiefly to the fertile lands in the
valley of the Rio Aconcagua, between Valparaiso and Los Andes, where there
are large cordage and twine mills. The fiber is all consumed in these
mills.

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