Stipule

In botany, stipule (Latin stipula: straw, stalk) is a term coined by Linnaeus which refers to outgrowths borne on either side (sometimes just one side) of the base of a leafstalk (the petiole). A pair of stipules is considered part of the anatomy of the leaf of a typical flowering plant, although in many species the stipules are inconspicuous or entirely absent (and the leaf is then termed exstipulate). In some older botanical writing, the term 'stipule' was used more generally to refer to any small leaves or leaf-parts, notably prophylls. In botany, stipule (Latin stipula: straw, stalk) is a term coined by Linnaeus which refers to outgrowths borne on either side (sometimes just one side) of the base of a leafstalk (the petiole). A pair of stipules is considered part of the anatomy of the leaf of a typical flowering plant, although in many species the stipules are inconspicuous or entirely absent (and the leaf is then termed exstipulate). In some older botanical writing, the term 'stipule' was used more generally to refer to any small leaves or leaf-parts, notably prophylls. The position of stipules on a plant varies widely from species to species, though they are often located near the base of a leaf. Stipules are most common on dicotyledons, where they appear in pairs alongside each leaf. Some monocotyledon plants display stipule-like structures, but only display one per leaf. A relationship exists between the anatomy of the stem node and the presence or absence of stipules: most plants with trilacunar nodes have stipules; species with unilacunar nodes lack stipules. Stipules are morphologically variable and might appear as glands, scales, hairs, spines, or laminar (leaf-like) structures. If a single stipule goes all the way around the stem, it is known as an ochrea. The three types of stipules according to duration are caducous, deciduous and persistent. Caducous stipules fall off before the leaf unfolds, while deciduous stipules fall off immediately after the leaf unfolds. Persistent stipules remain attached to the plant.