Petioles are long, and its cystoliths are largely punctiform. The cystoliths are extended to more or less rounded. Also useful is the varying appearance and arrangement of cystoliths on the leaf surface. Stems, stipules, petioles and blades are densely covered with spindle-shaped cystoliths. Cystoliths occur beneath the epidermis of the underside of the blade. Cystoliths are always present and some members of this family possess laticifers. Cystoliths are present in certain families, including in many genera of Acanthaceae. The leaves may contain cystoliths, calcium carbonate concretions, seen as streaks on the surface.