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Term	Definition
Inner integument extruded	An inner integument that is longer than the outer integument and forms the micropyle.
Inserted	Joined to or placed on; e.g., the stamens inserted on the corolla of Rubiaceae; also refers to stamens that do not extend beyond the corolla, in that case opposite of exserted.
Integument	The outer covering of the ovule that develops into the testa or seed coat; it may be composed of one or two layers, the inner and outer integuments, respectively.
Integument	The outer covering of the ovule that develops into the testa or seed coat; it may be composed of one or two layers, the inner and outer integuments, respectively.
Interfoliar	Borne among the leaves; e.g., the inflorescence of Attalea (Arecaceae).
International Code of Botanical Nomenclature (ICBN)	A set of rules governing the naming of plants. Every five years, the rules are reviewed at the International Botanical Congress and a new set of rules, many of which are the same, is published.
Internode	The part of the stem between nodes.
Interpetiolar	Located between the petioles of two opposite leaves; e.g., the stipules of Rubiaceae.
Intersecondary vein	A leaf vein that is intermediate in size between secondary and tertiary veins and often runs parallel to the secondary veins that it runs between. At about the middle between the midrib and the leaf blade margin intersecondary veins start to ramify dendritically.
Intersecondary vein	A leaf vein that is intermediate in size between secondary and tertiary veins and often runs parallel to the infra adjacent and supra adjacent secondary veins bounding it. At about the middle between the midrib and the leaf blade margin, intersecondary veins start to ramify dendritically.
Interseminal sinuses	The invaginations between the seeds in a legume pod.
Interspecific variation	Variation among populations of different species.
Intramarginal vein	A vein close to and parallel to the margin of a leaf.
Intrastaminal	Placed inside of the stamens; e.g., the discs of most Anacardiaceae and Meliaceae.
Intrastaminal disc	A fleshy, lobed, or annular nectariferous structure found within flowers between the stamens and the pistil. Preferred spelling is disc. Not to be confused with disk flower.
Invasive	A species of plant, animal, or microbe from one area that is introduced into an area where it was not present before and once established in the new habitat it causes economic damage, outcompetes native species thereby causing them to become less common, causes native species to be extirpated from some areas, or drives native species to extinction.
Involucre (diminutive = involucel)	A series of fused, overlapping, or free bracts that subtend inflorescences (e.g., in some Apiaceae, many Asteraceae, and Euphorbia of the Euphorbiaceae) or flowers (e.g., the female flowers of species of hickory (Carya spp.).
Irregular flower	A flower capable of being divided into only two equal parts (mirror images) by a line passing through the middle of a flower, i.e., other lines passing the middle of the flower will not give mirror images of one another; same as zygomorphic, monosymmetric, and bilaterally symmetrical, flowers and opposite of actinomorphic, monosymmetric, radially symmetrical, and regular flowers. This term can refer to other plant parts as well.
Isocotylar cotyledons	Cotyledons that are morphological identical
Isocotylous	Referring to seedlings in which both cotyledons are similar in shape and size. Compare with anisocotylous.
Isodromous	Referring to a venation pattern in which the first two veins in a given leaf segment arise opposite one another. Compare with anadromous and catadromous.
Isotype	A duplicate of the holotype. If a collection selected as the holotype has duplicates, the duplicates are called isotypes.
Iteropary (iteroparic or iteroparous)	Referring to plants that flower repeatedly; i.e., those that do not die after a single flowering. Same as polycarpic and pleionanthic; opposite of hapaxanthic and monocarpic.
Keel	Ridged like the bottom of a boat; same as carinate.The two lower, united petals of the flower of most species of Fabaceae subfamily Papilionoideae.
Keeled	Bearing a keel, same as carinate.
Keystone species	A species that plays a role in the survival of other species, such as by providing a source of food; e.g., species of Ficus (Moraceae).
Lamina	The expanded portion of a leaf or other structure such as a petal; when it is a leaf the narrowed part is the petiole and when it is a petal the narrowed part is the claw. Same as blade.
Laminate (laminated)	Arranged in layers, e.g., the outer bark of Lecythis pisonis..
Lanceolate	Lanceolate refers to a leaf, sepal, petal, or other flat structure that is wider at the base than at the midpoint, tapers toward the apex, and has a length-to-width ratio of 3:1 or more.
Lateral aril	An aril that runs along the side of the seed such as in many, but not all, species of Eschweilera (Lecythidaceae).
Lateral bud	A bud arising in the axil of a leaf. Same as axillary bud.
Lateral leaflet	In a pinnately compound leaf, the leaflets at inserted along the rachis. Note that pinnately compound leaves with lateral leaflets can be either imparipinnate ( = odd pinnate) or paripinnate (= even pinnate) depending on if there is a terminal or there is not a terminal leaflet, respectively.
Lateral style	Referring to a gynobasic style that arises from the base and side of the ovary.
Látex	Exudado blanco, cremoso o amarillo que usualmente emana a través de alguna herida en las plantas. Las especies de Clusiaceae usualmente emanan látex cuando son cortadas
Latex	Opaque, white, creamy, or yellow, free-flowing exudate, usually observed from a wound in a plant; species of Clusiaceae usually exude latex when wounded.
Latrorse	Directed toward the side, as the dehiscence of an anther; same as lateral. Compare with extrorse and introrse.
Leaf	An expanded stucture where photosynthesis takes place and usually consisiting of a petiole and a blade.
Leaf	A green, expanded stucture usually consisiting of a petiole and a blade but sometimes without a petiole in which photosynthesis takes place. When a petiole is absent the leaf is called sessile.
Leaf apex acuminate	Gradually tapering to an acute apex with the sides being concave.
Leaf apex acute	Sharp; usually referring to the apex of a flattened structure (such as a leaf) in which the two sides are straight and, when they meet, form an angle that is always less than 90°
Leaf apex attenuate	Tapering very gradually to a narrow tip.
Leaf apex emarginate	Markedly notched, such as the apex of a leaf or other structure.
Leaf apex mucronate	A sharp point at the apex of a leaf or a similar structure, e.g., a bract.
Leaf apex obtuse	Blunt, usually referring to the apex of a flattened structure (such as a leaf) in which the two sides are straight and, when they meet, form an angle greater than 90°.
Leaf apex retuse	Notched slightly at the apex.
Leaf apex rounded	Referring to a leaf blade base that is curved at the apex with an angle greater than 90 degrees at the point where the two sides meet.
Leaf apex truncate	Referring to an apex or base that terminates abruptly in a nearly straight horizontal edge.
Leaf asymmetrical	Referring to the form of a leaf in relation to the midrib, if the blade on each side of the midrib is unequal the leaf is asymmetrical.
Leaf base acute	Sharp; referring to the base of a leaf blade in which the two sides are straight and, when they meet, form an angle that is always less than 90°.
Leaf base asymmetric	Referring to a leaf base in which the two sides do not attach to the petiole at the same place, one is attached than the other.
Leaf base cordate	Heart-shaped at the base of a leaf blade. A cordate leaf blade always has a cordate base but a cordate leaf base may not always be associated with a cordate leaf blade.
Leaf base cuneate	Wedge-shaped; referring to the base of a leaf blade of which the angle formed by the meeting of the margins is less than 90°.
Leaf base decurrent	Referring to a leaf blade base that extends down the petiole.
Leaf base lobate (lobed)	A rounded projection arising from the base of a leaf blade.
Leaf base obtuse	Blunt, referring to the the base of a leaf blade in which the two sides are straight and, when they meet, form an angle greater than 90°.
Leaf base rounded	Referring to a leaf blade base that is curved at the apex with an angle greater than 90 degrees at the point where the two sides meet.
Leaf base sagittate	The base of a leaf blade shaped like an arrowhead.
Leaf base truncate	Referring to the base of a leaf blade that terminates abruptly in a nearly straight horizontal edge.
Leaf blade	The expanded portion of a leaf, it and the petiole combined equal the leaf. Same as lamina.
Leaf flush	The expansion of new leaves.
Leaf flush	The expansion of new leaves.
Leaf gap	A region of parenchyma in the vascular tissue of a stem that is located above the level where a leaf trace diverges from the stem toward the leaf.
Leaf margin crenate	Referring to a leaf blade margin with teeth rounded at the apex. Compare with serrate.
Leaf margin dentate	Referring to a leaf margin with sharp teeth oriented at right angles to the central axis of the leaf blade.
Leaf margin doubly serrate	Leaf blades with margins with sharp teeth oriented toward the apex with each touth in turn with a smaller tooth.
Leaf margin entire	Referring to leaf blade margins that are smooth, i.e., they have no serrations or crenations.
Leaf margin erose	Referring to leaf blade margin that is jagged, i.e., uneven but not with well-defined teeth.
Leaf margin lobed	Referring to rounded projections arising from the margins of a leaf blade that are cut less than one-half the distance to the midrib of the leaf blade, e.g., the leaves of the white oak group.
Leaf margin serrate	Leaf blades with margins with sharp teeth oriented toward the apex.
Leaf opposed	Referring to an inflorescence, infructescence, or tendril arising from the stem opposite a leaf.
Leaf scar	The scar left on a stem when a leaf falls.
Leaf sheath	Tubular, inrolled base of a leaf blade or petiole that surrounds the node and a portion of the internode; e.g., in the Cyperaceae, Poaceae, and many other monocotyledons as well as in some dicotyledons.
Leaf symmetrical	Referring to the form of a leaf with the blade equal on each side of the midrib.
Leaf symmetry	Referring to the form of a leaf in relation to the midrib, if the blade on each side of the midrib is equal the leaf is symmetrical and if the blades on each side of the midrib are not equal the leaf is asymmetrical.
Leaf venation acrodromous	Referring to a type of leaf venation in which two or more primary or strongly developed secondary veins arch upward from either the base or above it; perfect acrodromous is used when these veins converge near the apex; e.g., Strychnos (Loganiaceae); imperfect acrodromous is used when these veins do not converge at the apex. Based on Hickey, 1973. For more information about leaf venation see Ellis et al, 2009.

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