Stipule

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In botany, stipule refers to outgrowths borne on either side of the base of a leafstalk (or 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).

Stipules are morphologically variable and might appear as glands, scales, hairs, spines, or laminar (leaf-like) structures. 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 (Sinnott and Bailey, 1914, cited in Esau, 1953).

Leafy stipules at the base of a Rose leaf (Rosa canina)	Stipular spines accompanied by prickles of Euphorbia didieroides	Stipular spines on the mesquite tree (Prosopis pallida)]]	Glandular stipule of Euphorbia pteroneura
Stipules protecting young leaves of Carpinus betulus (European Hornbeam)	Fused together and leaf-like stipules of Alchemilla mollis	Stipules building glandular hairs on Jatropha spicata	Stipular spine clusters of Euphorbia spectabilis

[edit] References

• Esau, K. 1953. Plant Anatomy. Second Edition. John Wiley & Sons, Inc., New York, London, Sidney. 767 pp.
• Sinnott, E. W. and I. W. Bailey. 1914. Investigations on the phylogeny of the angiosperms. 3. Nodal anatomy and the morphology of stipules. Amer. J. Bot.,1: 441-453.