Cystolith (Gr. "cavity" and "stone") is a botanical term for the inorganic concretions, usually of calcium carbonate, formed in a cellulose matrix in special cells, generally in the leaf of plants of certain families, for example Ficus elastica, the Indian rubber plant. Plants in the family Urtica, also known as Stinging Nettles, also form leaf cystoliths, but only during their later flowering and seed setting stages.… (More on Cystolith)