the distribution of leaves of plants in a single plane, usually perpendicular to light rays, which provides the least shading of leaves by one another. Leaf mosaic is caused by the unequal growth of petioles and leaf blades that are drawn to light and fill every space exposed to the sun’s rays. As a result, the size and even the shape of leaves are altered. Leaf mosaic may be observed on the horizontal and, more rarely, on the vertical branches of trees and shrubs under conditions of considerable shade (the lower branches of the crowns of elm, linden, and maple trees), on the stolons of herbs (asarum), and on rosette shoots (geranium, plantago, dandelion). Leaf mosaic is an important adaptation which makes maximum use of dispersed light and can be formed with any type of leaf arrangement—spiral, opposite, or verticillate.