Cannabis sativa is an annual herbaceous flowering plant indigenous to Eastern Asia, but now of cosmopolitan distribution due to widespread cultivation. It has been cultivated throughout recorded history, used as a source of industrial fiber, seed oil, food, recreation, religious and spiritual moods and medicine. Each part of the plant is harvested differently, depending on the purpose of its use. The species was first classified by Carl Linnaeus in 1753. The word sativa means "things that are cultivated." Plant physiology The flowers of Cannabis sativa are unisexual and plants are most often either male or female. It is a short-day flowering plant, with staminate (male) plants usually taller and less robust than pistillate (female or male) plants. The flowers of the female plant are arranged in racemes and can produce hundreds of seeds. Male plants shed their pollen and die several weeks prior to seed ripening on the female plants. Under typical conditions with a light period of 12 to 14 hours, both sexes are produced in equal numbers because of heritable X and Y chromosomes. Although genetic factors dispose a plant to become male or female, environmental factors including the diurnal light cycle can alter sexual expression. Naturally occurring monoecious plants, with both male and female parts, are either sterile or fertile; but artificially induced "hermaphrodites" can have fully functional reproductive organs. "Feminized" seed sold by many commercial seed suppliers are derived from artificially "hermaphroditic" females that lack the male gene, or by treating the plants with hormones or silver thiosulfate. Pharmacology Although the main psychoactive constituent of Cannabis is tetrahydrocannabinol (THC), the plant is known to contain more than 500 compounds, among them at least 113 cannabinoids; however, most of these "minor" cannabinoids are only produced in trace amounts. Besides THC, another cannabinoid produced in high concentrations by some plants is cannabidiol (CBD), which is not psychoactive but has recently been shown to block the effect of THC in the nervous system. Differences in the chemical composition of Cannabis varieties may produce different effects in humans. Synthetic THC, called dronabinol, does not contain cannabidiol (CBD), cannabinol (CBN), or other cannabinoids, which is one reason why its pharmacological effects may differ significantly from those of natural Cannabis preparations. Chemical constituents Beside cannabinoids, the chemical constituents of Cannabis include about 120 compounds responsible for its characteristic aroma. These are mainly volatile terpenes and sesquiterpenes. α-Pinene Myrcene Linalool Limonene Trans-β-ocimene α-Terpinolene