"Botanically, the genus Cannabis is composed of several variants. Although there has been a long-standing debate among taxonomists about how to classify these variants into species, applied plant breeders generally embrace a biochemical method to classify variants along utilitarian lines. Cannabis is the only plant genus that contains the unique class of molecular compounds called cannabinoids. Many cannabinoids have been identified, but two preponderate: THC, which is the psychoactive ingredient of Cannabis, and CBD, which is an antipsychoactive ingredient. One type of Cannabis is high in the psychoactive cannabinoid, THC, and low in the antipsychoactive cannabinoid, CBD. This type is popularly known as marijuana. Another type is high in CBD and low in THC. Variants of this type are called industrial hemp."
[Hemp and Marijuana: Myths & Realities (Abstract Version); David P. West, Ph.D.]
"Scientists who were the first to study the genus Cannabis clearly discerned different species. The father of plant taxonomy, Linnaeus, officially designated the Cannabis genus in 1753 when he founded the binomial system of botanical nomenclature still used today [4]. Linnaeus added the "sativa" appellation (literally, "sown" or "cultivated," i.e., used in agriculture), indicating the utilitarian nature of the plant. Since his time numerous attempts have been made for a coherent taxonomy of Cannabis. Species designations have come and gone [5]. . . "
" . . . In 1889, botanist and plant explorer George Watt wrote about the distinction between types of Cannabis : "A few plants such as the potato, tomato, poppy and hemp seem to have the power of growing with equal luxuriance under almost any climatic condition, changing or modifying some important function as if to adapt themselves to the altered circumstance. As remarked, hemp is perhaps the most notable example of this; hence, it produces a valuable fibre in Europe, while showing little or no tendency to produce the narcotic principle which in Asia constitutes its chief value."[6] . . ."
" . . . The key Cannabis species problem derives from the fact that there is no convenient species barrier between the varying types that would allow us to draw a clear line between them. In taxonomy, often the delineating line between species is that they cannot cross-breed. But disparate types of Cannabis can indeed produce fertile offspring, not sexually dysfunctional "mules."" . . .
" . . . The prevailing opinion currently recognizes three species: C. sativa, C. indica, and C. ruderalis. [10] "Industrial" types fall exclusively within C. sativa, although all Cannabis plants contain stem fiber and can have multiple uses in primitive societies where they are indigenous." . . .
" . . . Recent analytical advances are leading many scientists to believe that a more accurate and satisfying way to differentiate the different forms of Cannabis would be by their biochemical composition."
" . . . Thus, using the chemotype approach, Cannabis variants can be classified on the basis of their THC-CBD balance. This is accepted by a growing number of scientists. Gabriel Nahas, M.D., Ph.D., writes, "One should still distinguish two principal large groups of varieties of Cannabis sativa , the drug type and the fiber type. In addition to this classical distinction of these two groups, botanists generally accept description consisting of three chemical types: (a) the pure drug type, high THC content (2-6 percent) and lacking CBD[cannabidiol]; (b) the "intermediate type" (predominantly THC); and (c) the fiber type (THC<0.25 percent)." [16]"
" . . . he 1937 Marijuana Tax Act defined marijuana as: "(A)ll parts of the plant Cannabis sativa L., whether growing or not; the seeds thereof; the resin extracted from any such plant; and every compound, manufacture, salt, derivative, mixture, or preparation of such plant, its seeds, or resin; but shall not include the mature stalks of such plant, fiber produced from such stalks, oil or cake made from the seeds of such plant, any other compound, manufacture salt, derivative, mixture, or preparation of such mature stalks (except the resin extracted therefrom), fiber, oil, or cake, or the sterilized seed of such plant which is incapable of germination." [18]"