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]

A. Leaf Parts

Blade. Flat, expanded portion of leaf.
Leaflet. A distinct and separate segment of a leaf.
Ligule. An outgrowth or projection from the top of the sheath, as in the Poaceae.
Midrib. The central conducting and supporting structure of the blade of a simple leaf.
Midvein. The central conducting and supporting structure of the blade of a leaflet.
Petiole. Leaf stalk.
Petiolule. Leaflet stalk.
Pulvinus. The swollen base of a petiole or petiolule.
Rachilla. Secondary axis of compound leaf.
Rachis. The main axis of a pinnately compound leaf.
Sheath. Any more or less tubular portion of the leaf surrounding the stem or culm, as in the Poaceae.
Stipels. Paired scales, spines, or glands at the base of petiolule.
Stipules. Paired scales, spines, glands, or blade-like structures at the base of a petiole.

B. Leaf Types (Figure 6-3-1) (Figure 6-03-2)
(Classification based primarily on arrangement of leaflets)

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.

Bifoliolate, Geminate, or Jugate. With two leaflets from a common point.
Bigeminate, Bijugate. With two orders of leaflets, each bifoliolate; doubly paired.
Bipalmately Compound. With two orders of leaflets, each palmately compound.
Bipinnately Compound. With two orders of leaflets, each pinnately compound.
Biternate. With two orders of leaflets, each ternately compound.
Compound. With leaf divided into two or more leaflets.
Decompound. A general term for leaflets in two or more orders - bi-, tri-etc. - pinnately, palmately, or ternately compound.
Imparipinnately Compound. Odd-pinnately compound, with a terminal leaflet.
Interruptedly Pinnately Compound. With smaller and larger leaflets alternating along the rachis.
Palmately Compound. With leaflets from one point at end of petiole.
Palmate-pinnate. With first order leaflets palmately arranged, second order pinnately arranged.
Paripinnately Compound. Even-pinnately compound, without a terminal leaflet.
Pinnately Compound. With leaflets arranged oppositely or alternately along a common axis, the rachis.
Simple. With leaf not divided into leaflets.
Tergeminate. With three orders of leaflets, each bifoliolate, or with geminate leaflets ternately compound.
Ternately Compound. With leaflets in three's.
Trifoliolate. With leaflets three, pinnately compound with terminal petiolule longer than lateral; or palmately compound with petiolules equal in length.
Tripalmately Compound. With three orders of leaflets, each palmately compound.
Tripinnately Compound. With three orders of leaflets, each pinnately compound.
Triternate. With three orders of leaflets, each ternately compound.
Unifoliolate. With a single leaflet with a petiolule distinct from the petiole of the whole leaf, as in Cercis.

C. Leaf Structural Types(Figure 6-3-3)

Bract. Modified leaf found in the inflorescence.
Bracteole or Prophyllum. Small leaf, usually on a pedicel.
Chaff or Pale. Scale or bract at base of tubular flower in composites.
Complete. Leaf with blade, petiole, and stipules.
Cotyledon. Embryonic leaf.
Elaminate. Without blade.
Epetiolate. Without petiole, leaf sessile.
Epetiolulate. Without petiolule, leaflet sessile.
Epicalyx. Group of leaves resembling sepals below the true calyx.
Exstipellate. Without stipels.
Exstipulate. Without stipules.
Fly Trap. Hinged, insectivorous leaf, as in Dionaea.
Glume. Bract, usually occurring in pairs, at the base of the grass spikelet.
Incomplete. Leaf without one or more parts: blade, petiole, stipules.
Lemma. Outer scale subtending grass floret.
Palea. Inner scale subtending grass floret.
Phyllary. One of the involucral leaves subtending a capitulum, as in composites.
Phyllodium. Flattened blade-like petiole or midrib.
Pitcher. Ventricose to tubular insectivorous leaf, as in Sarracenia.
Scale. Small, non-green leaf on bud and modified stem.
Spathe. An enlarged bract enclosing an inflorescence.
Spine. Sharp-pointed petiole, midrib, vein, or stipule.
Sporophyll. A spore bearing leaf.
Storage Leaf. Succulent, fleshy leaf.
Tendril. Usually a coiled rachis or twining leaflet modification.
Tentacular. Glandular-haired or tentacle-bearing insectivorous leaf, as in Drosera.

D. Petiole and Petiolule Structural Types

Channelled or Canaliculate. With a longitudinal groove.
Inflated. Swollen or thickened, as in Eichhornia.
Pericladial. With a sheathing base, as in the Apiaceae.
Petiolate. With a petiole.
Petiolulate. With a petiolule.
Phyllodial. Flattened and blade-like.
Pulvinal. With a swollen base, as in the Fabaceae.
Sessile or Absent. Without petiole or petiolule.
Winged. With flattened blade-like margins.

E. Stipule and Stipel Types
(Classification based primarily on attachment or function)

Adnate. With stipule attached to petiole.
Basal. With stipules attached near base of petiole.
Interpetiolar. With connate stipules from two opposite leaves.
Lateral. With stipules adnate to petiole and free part of stipules located along the petiole.
Median. With stipules adnate to petiole with free part of stipules near middle of petiole.
Photosynthetic. Blade-like and green.
Sheathing or Protective. Enclosing a bud or flower.
Stipellate. With stipels.
Stipulate. With stipules.
Vestigial. Minute; a remnant.