Acanthaceae is a family (the acanthus family) of dicotyledonous flowering plants containing almost 250 genera and about 2500 species. Most are tropical herbs, shrubs, or twining vines; some are epiphytes. Plants in this family have simple, opposite, decussated leaves with entire (or sometimes toothed, lobed, or spiny) margins, and without stipules. The leaves may contain cystoliths, calcium carbonate concretions, seen as streaks on the surface.