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Published In: Species Plantarum 2: 1027. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 8/11/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status: Introduced

 

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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.

 


 

 
 
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