The Datura genus of plants, especially Datura stramonium and related species, contain psychoactive and potentially dangerous levels of tropane alkaloids atropine, hyoscyamine, and scopolamine. Hyoscyamine is just a specific name for the levorotrary (l-) stereo isomer of atropine and is sometimes lumped in with atropine, where atropine is usually a mixture of l- and r-isomers. The ratios of the different psychoactive tropane alkaloids vary between parts of the pland and change during the growing cycle.