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Analysis And Comment Science commentary

Cannabis confusions

BMJ 2006; 332 doi: (Published 19 January 2006) Cite this as: BMJ 2006;332:175
  1. Geoff Watts, science editor, BMJ (
  1. London NW3 1LS

    Debates about cannabis are not confined to its value as a medicine or to its possible hazards as a recreational drug.1 Something much more fundamental has been engaging the experts for years: its taxonomy. Are all plants belonging to the genus Cannabis mere varieties of a single species—or is it correct to recognise at least three separate species?

    In his original 1753 classification, Carl Linnaeus identified just one, Cannabis sativa. The first indication of dissent came in 1785 when another eminent biologist, Jean-Baptiste Lamarck, was given some plant specimens collected in India. On the basis of several characteristics including their firm stems, thin bark, and the shape of their leaves and flowers, Lamarck felt that they should be distinguished from C sativa. Accordingly he invoked a new species, C indica.

    In a lengthy and detailed review of the cannabis species problem, Ernest Small of the Canadian Biosystematics Research Institute commented that Lamarck seems to have reached his …

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