Fig. 3.6-4. Transverse section through a leaf of ice plant (Mesembryanthemum crystallinum). The large circle protruding from the surface of the leaf is an epidermis cell that stores water. It has a volume hundreds of times larger than that of other parenchyma cells in the leaf, so its water storage capacity is comparatively great, but it also has a large surface area through which water can be lost to the air. The nucleus-to-cytoplasm ratio in this cell is extremely low, but water storage is a simple metabolism and the cell probably does not need a great deal of nuclear control.