Lithocyst. Light micrograph of a section through the surface of a fig leaf Ficus sp. , showing a specialised cell known as a lithocyst. The lumen of the cell contains an outgrowth of the cell wall on which is deposited a concretion of calcium carbonate crystal (lime). The mass of calcium carbonate is itself known as a cystolith. Litho- cysts occur in relatively few plant species; the rubber plant (Ficus elastica) is one of the most common examples. The function of these specialised cells is unknown. Magnification: x200 at 35mm size.