Cystolith

thumb|Cystolith from leaf of Ficus elastica thumb|Drawing of a cystolith from leaf of Ficus elastica

Cystolith (Gr. "cavity" and "stone") is a botanical term for outgrowths of the epidermal cell wall, usually of calcium carbonate but sometimes of silicon dioxide also, formed in a cellulose matrix in special cells called lithocysts, generally in the leaf of plants.