Leaf

A usually green, flattened structure attached to the stem that functions as the principal organ of photosynthesis and transpiration in most plants.

In Dicotyledons, the leaf is typically rounded and divided into a flattened blade and stalk. In Monocotyledons, it tends to be elongated and strap-like with parallel veins. Leaves can be modified to form hooks, tendrils and other structures for secondary roles.