| Leaves vary in size and shape. The slender petiole or | | | | compound leaves, the leaf blade may be subdivided |
| leaf stalk is present in the leaves of most flowering | | | | into several separate expanded parts, or leaflets. Each |
| plants. It is a continuation of the stem to the rest of the | | | | leaflet may consist of an extended portion and a short |
| leaf. Leaves without a petiole are called sessile. The | | | | stalk attached to the rachis, which is a continuation of |
| blade is the flattened, expanded portion of the leaf and | | | | the petiole. Leaves may be pinnately compound or |
| is usually green. Some leaf blades are needle like as in | | | | bipinnately compound. |
| pines or scale like as in cypresses. Some leaves have | | | | Leaf venation, the arrangement of veins in a leaf, may |
| small, leaf like stipules as outgrowths at the base of | | | | be parallel or netted. Parallel venation is a characteristic |
| the petiole. Running through the center of the blade is | | | | of most monocotyledonous plants, such as corn, onion |
| the midrib which is the continuation of the petiole. The | | | | and common grasses. In such plants, numerous veins |
| midrib is the main structure which acts as the | | | | of approximately equal size extend side by side from |
| backbone of the leaf and as a passage tube for liquids | | | | the base to the tip of the blade and are interconnected |
| between the petiole and veins. The veins act as the | | | | by small and inconspicuous veins. Net venation is found |
| framework of the leaf and as passage tubes for | | | | in dicotyledonous plants such as mangoes. In these |
| liquids between the midrib and the blade. The veins | | | | plants one or more veins are prominent and the |
| also distinguish a monocot leaf from a dicot leaf. | | | | smaller veins form a conspicuous network. If a leaf |
| Leaves may be simple, compound, or bicompound. | | | | has one main vein from which the others branch off, it |
| Simple leaves have a single expanded portion. In | | | | is termed pinnately net veined. |