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Section A. Structure and Specialized Characters:
V. Leaves
[A. Leaf Parts] [B. Leaf Types] [C. Leaf Structural Types] [D. Petiole and Petiolule Structural Types] [E. Stipule and Stipel Types]
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Blade. Flat, expanded portion of leaf.
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Leaflet. A distinct and separate segment of a leaf.
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Ligule. An outgrowth or projection from the top of the sheath, as in the Poaceae.
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Midrib. The central conducting and supporting structure of the blade of a simple leaf.
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Midvein. The central conducting and supporting structure of the blade of a leaflet.
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Petiole. Leaf stalk.
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Petiolule. Leaflet stalk.
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Pulvinus. The swollen base of a petiole or petiolule.
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Rachilla. Secondary axis of compound leaf.
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Rachis. The main axis of a pinnately compound leaf.
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Sheath. Any more or less tubular portion of the leaf surrounding the stem or culm, as in the Poaceae.
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Stipels. Paired scales, spines, or glands at the base of petiolule.
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Stipules. Paired scales, spines, glands, or blade-like structures at the base of a petiole.
Note: This classification is based on discrete segments of leaves or leaflets, but the terms with "compound" are equally applicable to segments, divisions, etc. of any structure with a blade; e.g., palmately divided, pinnately cleft, etc.
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Bifoliolate, Geminate, or Jugate. With two leaflets from a common point.
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Bigeminate, Bijugate. With two orders of leaflets, each bifoliolate; doubly paired.
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Bipalmately Compound. With two orders of leaflets, each palmately compound.
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Bipinnately Compound. With two orders of leaflets, each pinnately compound.
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Biternate. With two orders of leaflets, each ternately compound.
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Compound. With leaf divided into two or more leaflets.
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Decompound. A general term for leaflets in two or more orders - bi-, tri-etc. - pinnately, palmately, or ternately compound.
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Imparipinnately Compound. Odd-pinnately compound, with a terminal leaflet.
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Interruptedly Pinnately Compound. With smaller and larger leaflets alternating along the rachis.
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Palmately Compound. With leaflets from one point at end of petiole.
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Palmate-pinnate. With first order leaflets palmately arranged, second order pinnately arranged.
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Paripinnately Compound. Even-pinnately compound, without a terminal leaflet.
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Pinnately Compound. With leaflets arranged oppositely or alternately along a common axis, the rachis.
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Simple. With leaf not divided into leaflets.
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Tergeminate. With three orders of leaflets, each bifoliolate, or with geminate leaflets ternately compound.
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Ternately Compound. With leaflets in three's.
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Trifoliolate. With leaflets three, pinnately compound with terminal petiolule longer than lateral; or palmately compound with petiolules equal in length.
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Tripalmately Compound. With three orders of leaflets, each palmately compound.
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Tripinnately Compound. With three orders of leaflets, each pinnately compound.
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Triternate. With three orders of leaflets, each ternately compound.
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Unifoliolate. With a single leaflet with a petiolule distinct from the petiole of the whole leaf, as in Cercis.
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Bract. Modified leaf found in the inflorescence.
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Bracteole or Prophyllum. Small leaf, usually on a pedicel.
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Chaff or Pale. Scale or bract at base of tubular flower in composites.
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Complete. Leaf with blade, petiole, and stipules.
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Cotyledon. Embryonic leaf.
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Elaminate. Without blade.
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Epetiolate. Without petiole, leaf sessile.
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Epetiolulate. Without petiolule, leaflet sessile.
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Epicalyx. Group of leaves resembling sepals below the true calyx.
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Exstipellate. Without stipels.
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Exstipulate. Without stipules.
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Fly Trap. Hinged, insectivorous leaf, as in Dionaea.
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Glume. Bract, usually occurring in pairs, at the base of the grass spikelet.
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Incomplete. Leaf without one or more parts: blade, petiole, stipules.
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Lemma. Outer scale subtending grass floret.
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Palea. Inner scale subtending grass floret.
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Phyllary. One of the involucral leaves subtending a capitulum, as in composites.
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Phyllodium. Flattened blade-like petiole or midrib.
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Pitcher. Ventricose to tubular insectivorous leaf, as in Sarracenia.
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Scale. Small, non-green leaf on bud and modified stem.
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Spathe. An enlarged bract enclosing an inflorescence.
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Spine. Sharp-pointed petiole, midrib, vein, or stipule.
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Sporophyll. A spore bearing leaf.
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Storage Leaf. Succulent, fleshy leaf.
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Tendril. Usually a coiled rachis or twining leaflet modification.
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Tentacular. Glandular-haired or tentacle-bearing insectivorous leaf, as in Drosera.
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Channelled or Canaliculate. With a longitudinal groove.
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Inflated. Swollen or thickened, as in Eichhornia.
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Pericladial. With a sheathing base, as in the Apiaceae.
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Petiolate. With a petiole.
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Petiolulate. With a petiolule.
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Phyllodial. Flattened and blade-like.
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Pulvinal. With a swollen base, as in the Fabaceae.
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Sessile or Absent. Without petiole or petiolule.
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Winged. With flattened blade-like margins.
E. Stipule and Stipel Types
(Classification based primarily on attachment or function)
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Adnate. With stipule attached to petiole.
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Basal. With stipules attached near base of petiole.
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Interpetiolar. With connate stipules from two opposite leaves.
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Lateral. With stipules adnate to petiole and free part of stipules located along the petiole.
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Median. With stipules adnate to petiole with free part of stipules near middle of petiole.
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Photosynthetic. Blade-like and green.
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Sheathing or Protective. Enclosing a bud or flower.
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Stipellate. With stipels.
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Stipulate. With stipules.
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Vestigial. Minute; a remnant.
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