Leaf - Blade

The size and shape of the blade are often characteristic of a species, and are useful in species identification. However, the leaf blades of some species, such as those of oaks (Quercus), exhibit great variation in size and shape, sometimes even when on the same tree. Botanists use a large vocabulary of specialized terms to describe the leaf outline, margin, apex, base, and vestiture (surface covering). For example, Pine (Pinus) leaves are considered acicular, meaning they are shaped like a needle; Aspen (Populus) leaves are considered ovate, meaning they resemble a two-dimensional projection of an egg; May apple (Podophyllum) leaves are considered peltate, meaning they are shaped like a shield, and are attached to the stalk on the lower leaf surface.