1. Cannabis sativa L. (hemp, marijuana)
C. sativa var. spontanea Vavilov
C. ruderalis Janish.
Pl. 333 a, b;
Map 1418
Plants annuals,
with long taproots, aromatic, the staminate plants mostly taller, more slender,
and with sparser leaves than the pistillate ones. Stems 50–500 cm tall, erect,
usually with numerous branches, usually coarsely ridged, often hollow at
maturity, moderately pubescent with unbranched appressed-ascending hairs, also
sparsely dotted with resinous glands. Leaves with the petioles 2–7 cm long,
pubescent with unbranched hairs. Stipules narrowly triangular, not fused. Leaf
blades palmately compound with mostly 5–9 unequal leaflets, the leaflets
sessile or nearly so, 3–17 cm long, 0.3–2.0 cm wide, linear to narrowly
lanceolate or narrowly elliptic, tapered at the base, tapered to a sharply
pointed tip, the margins coarsely and sharply toothed, the upper surface
sparsely pubescent with unbranched hairs and dotted with yellowish brown
resinous glands, the hairs with inflated bases and cystoliths, dark green, the
undersurface moderately to densely appressed-hairy and with scattered resinous
gland-dots and sometimes also stalked glands, pale green. Staminate
inflorescences appearing as short panicles consisting of small flower clusters
on nearly leafless branches, the flowers with stalks 0.5–3.0 mm long.
Pistillate inflorescences consisting of small clusters on short, leafy,
spikelike branches, ascending at maturity, not conelike, sparsely to densely
covered with stalked or nearly sessile glands, the flowers sessile or nearly
so, the bracts lanceolate. Staminate flowers 2.5–4.0 mm long, the sepals
lanceolate to ovate, with pale, thin margins, minutely hairy. Pistillate
flowers with the ovary 2–3 mm long at flowering. Fruits 3–4 mm long, ovoid,
somewhat flattened, enveloped by the persistent glandular bracts and membranous
calyx, pale green to light brownish green, often somewhat purplish-mottled. 2n=20.
July–October.
Introduced,
scattered, mostly in the northern half of the state, locally common in some
portions of northwesternmost Missouri (cultigen presumably native to western
Asia; cultivated and introduced nearly worldwide). Banks of streams and rivers,
edges of marshes, and disturbed portions of bottomland, upland, and loess hill
prairies; also levees, ditches, fencerows, gardens, margins of crop fields,
railroads, roadsides, and open, disturbed places.
Cannabis
sativa is a remarkable
plant with many uses and a fascinating history (Dewey, 1914; Miller, 1970;
Abel, 1980; Brown, 1998). Some races have been bred for fiber production, for
the long fibers of the stem are used to make rope, twine, bags, nets, cloth,
and paper. Some races have been selected for their fruits, which can be eaten
(usually roasted) by humans and are often used in bird seed mixtures. The seeds
contain an oil that can be used in the manufacture of paints, varnish,
lubricants, and soaps, and as a fuel for lamps or even diesel engines. In other
races, the leaves and pistillate inflorescences produce a resin used medicinally
to treat a wide range of ailments (Brown, 1998; Grotenhermen and Russo, 2002),
and that in more recent years has been adopted by modern medicine for the
treatment of glaucoma and to ameliorate the side effects of chemotherapy in the
treatment of cancer. When used as a drug, marijuana consists of plant fragments
(mostly of pistillate inflorescences and associated leaves) that are burned and
the smoke inhaled with various narcotic and hallucinogenic effects. Hashish is
a more purified resin from the same source that also usually is smoked. The use
of these substances as recreational drugs is illegal in most of the developed
world, including the United States, although in a few states the possession of
small amounts of marijuana has become decriminalized in recent years. The resin
involved is most concentrated in the pistillate flower buds and contains
terpenoids known as cannabinols, the most potent of which are isomers of
tetrahydrocannabinol (THC).
Cannabis
sativa appears to be one
of mankind’s oldest cultivated plants. It apparently originated in central Asia
north of the Himalayas and was cultivated in China for thousands of years. It
also was used by the ancient Assyrians, Scythians, Indians, and Greeks. Cannabis
spread to Africa very early, where it assumed great importance in many
cultures. It was brought to Europe by 1500 BC and was widely grown for fiber by
AD 500. Spanish conquistadors and English pilgrims brought Cannabis to
the New World. Prior to the Civil War, hemp was a major crop in the United
States for the rope industry. In Missouri, it was a leading crop in Saline,
Lafayette, and other counties along the Missouri River. Hemp also was grown
during World War II when the Japanese armed forces cut off access to supplies
of Manila rope.
Cannabis
sativa is a highly
variable species, due to a natural genetic plasticity, long selection by
humans, a wide distribution, and its response to varied environmental factors.
Several additional species have been described, and there has been much debate
about whether these taxa should be accepted or not (Small, 1979; Small and
Cronquist, 1976). Cannabis indica Lam. was based on plants from the East
Indies that are smaller than typical C. sativa, with somewhat firmer,
narrower, mostly alternate leaves. In his original description, Lamarck (1785)
mentioned its intoxicating properties, and the name is associated to the
present day with low-growing plants with small seeds selected for their use as
drugs. The names C. sativa var. spontanea and C. ruderalis
were described for plants from Russia with so-called wild characteristics such
as smaller, harder, and more readily disarticulating fruits. Some botanists
believe that at least 3 species of Cannabis exist (Emboden, 1974) or
maintain that they might exist (Schultes and Hofmann, 1980). Alternatively,
Small and Cronquist (1976) argued for the existence of a single species, C.
sativa, and provided an infraspecific classification with two subspecies,
ssp. sativa and ssp. indica (Lam.) E. Small & Cronquist, plus
two varieties of each. These authors pointed out that variation is continuous,
there are no barriers to interbreeding, and that these taxa are maintained
through continued natural and artificial selection. Their two subspecies are
separated by the percentage (based on dry weight) of THC in the upper portions
of plants (0.3 percent being the arbitrary separation), rather than
morphological features. Within each subspecies, Small and Cronquist segregated
a cultivated variety, with larger, longer-persistent fruits with a somewhat
less-persistent calyx, from a variety having more so-called wild-type
characteristics. Several authors (Barker and Brooks, 1986) have noted that
cultivated hemp plants that have been naturalized in the wild begin to revert
back to the wild type as selection favors plants with more easily dispersed
fruits. This is true in Missouri populations, many of which have fruits smaller
than the arbitrary 3.8 mm length used by Small and Cronquist to distinguish
varieties. Although a formal infraspecific classification has use for plant
breeders and law enforcement officials, it has limited practical value for
botanists dealing with plants growing outside of cultivation in Missouri.
Wild populations
found in Missouri more or less correspond to ssp. sativa, the taxon that
once was widely grown for fiber production and is now a common weed. There are
only sporadic occurrences of one or a few plants (mostly in urban areas) of the
drug plant, ssp. indica, which apparently does not reproduce itself
sufficiently outside of cultivation to form persistent populations. Currently,
it is illegal to grow or possess any species of Cannabis in Missouri,
and state law enforcement officials eradicate numerous wild and cultivated
plants each year. Although hemp cultivation is legal in many countries,
attempts to legalize it in the United States for industrial hemp production
have met with stiff resistance.