Tree Atlas Glossary


Abrupt – Suddenly ending, as though broken off.
Acicular – Very narrow, stiff and pointed, needle-shaped.
Acuminate – Having a gradually diminishing point, drawn out.
Acute – Distinctly and sharply pointed, but not drawn out.
Adherent – When separate parts that are normally apart are joined.
Adnate – United with another part.
Adventitious – Of structures found elsewhere from where they usually occur, like adventitious buds (buds arising in the bark of stems), or adventitious roots (roots that come down from the lower stem or even from branches).
Alternate – Of leaves when they are arranged along the twigs with some distance between subsequent leaves. In other words: there is only one leaf at each NODE, as distinct from OPPOSITE. When arranged in two rows along the twig leaves are DISTICHOUS. See also: OPPOSITE, WHORL, CLUSTERED, LEAFLET. In pinnately compound leaves the leaflets can be alternate or (sub-)opposite.
Alternate – SIMPLE & DISTICHOUS leaves with a DRIP TIP. This might seem like a pinnate leaf, but the flower buds in the axils of some of the leaves prove that these are entire, simple leaves and not leaflets.
Angular – Not round on crossection: the angular fruit of Nesogordonia; ribbed.
Annular – Like a ring, e.g. the annular ring around the twig, left behind after the stipule that covered the terminal bud has fallen off. Annular rings are very common in Ficus, and in Moraceae in general.
Apex – The top of an organ, e.g. the tip of a leaf, of a twig, of a fruit. In this case the acute apex of a leaf; one could also say leaf tip.
Apicular – Placed or positioned at the top or apex.
Apiculate – Abruptly ending in a point.
Arched – Bent or curved; see also: LOOPING.
Aril – An often brightly coloured structure arising from the stalk of the seed, partly or totally covering the seed.
Armed – When the stem and/or the branches of the tree has THORNS (general term) or SPINES or PRICKELS (more specific terms).
Articulate – Jointed, hinged, or separating at a certain point.
Ascending – Arising steeply upwards: ascending laterals, ascending branches.
Asymmetric – When both halves of the BLADE, on either side of the MIDRIB, are shaped differently; also: both halves of a fruit being different. See also UNEQUAL-SIDED and SYMMETRIC.
Attenuate – Narrowed, tapered.
Auriculate -Having an ear-like appendage at the base of a BLADE. See also LEAF-SHAPE.
Axil – The (mostly angled) space between the petiole and the twig. Axillary: arising from the axil, usually at the NODES. Axillary buds, inflorescence, flowers, fruits.
Axis – The central part of a structure (a tree crown, an inflorescence) from which other parts arise.


Bark – The outer layer of a stem, branch, twig, root; all tissues outside the CAMBIUM. Inside the bark one can, generally, see three types of tissue: the still living inner bark, closest to the wood; DILATATION tissue to help the inner bark keep up with circumference growth resulting from the diameter growth of the stem; OUTER BARK of dead tissue, often differently coloured, sometimes thick, sometimes very thin, and peeling off in often characteristic fashion.
Bark patterns – Characteristic (but not complete) patterns in bark.
Bark ray – Mostly very narrow but long, vertical structures in the inner bark that serve transport of oxygen into the living tissues in the tree: cambium, sap wood. In a slash often visible as tiny narrow, vertical, lens-shaped structures. See also LENTICEL and WOOD RAY.
Basal – At the base of an organ, e.g. a leaf: referring to the base of the BLADE, from where a few or more strong NERVES arise. When the central nerve is the strongest that is the MIDRIB of a PENNI-NERVED leaf, and the basal nerves are the first LATERALS. When all nerves are ± equal, spreading out like the fingers of a hand, this is a PALMATE leaf.
Base – The lowest extremity of a body, e.g. of a tree or a blade.
Beaked – Used to describe fruits that end in a long, often curved point.
Bell-shaped – tubular, rounded and inflated, wider at one side.
Berry – A juicy fruit with the seeds immersed in the fruit pulp.
Bifoliolate – When the blade of a COMPOUND leaf is subdivided into only two LEAFLETS, having only one pair of leaflets. In many species this is a very constant character but some species have both bifoliolate leaves (only one pair of leaflets) and leaves with more pairs of leaflets.
Bilobed – Divided into two lobes.
Bilocular – With two compartments or cells.
Bipartite – Of a BLADE that is divided nearly to the base into two portions.
Bipinnate – When the leaflets of a PINNATE leaf are themselves again subdivided into smaller units. These smallest subdivisions or leaflets are arranged along a common axis, the secondary RACHIS; leaflets + secondary rachis together form a PINNA (plural: pinnae). Sometimes leaflets are tiny, sometimes small, sometimes “normal”, a few cm long. No bipinnate leaves with large leaflets occur in Liberia.
Bipinnate – Special forms. Some bipinnate species have leaves with only one pair of pinnae; other species have a few to many pairs of pinnae. The pinnae can be OPPOSITE or sub-opposite. The leaflets themselves can be opposite or alternate. Sometimes a pinna counts only 2 leaflets.
Bisexual – Having both sexes (stamens and ovary) in the same flower or inflorescence.
Blade– The flat, usually green part of a LEAF or LEAFLET (lamina, limb). The blade can be ENTIRE, forming one undivided unit, or subdivided into smaller parts: LEAFLETS of a COMPOUND leaf. The blade is the organ of a plant where PHOTOSYNTHESIS takes place.
Blunt – Ending in a rounded form, neither tapering to a point, nor abruptly cut off.
Bole – The main, mostly erect stem of a tree.
Bony – Of a dense and hard texture.
Bordered – Of a blade (or fruit or seed) having a margin distinct in colour or texture from the rest.
Bract – A small, usually specially-shaped leaf at the base of a flower or inflorescence.
Branch – A division of the stem or axis of growth; all branches of a tree together form its crown.
Bristle – Stiff hair.
Broadly – Expressing that the length:width ratio of a flat surface (e.g. a blade) varies between 3:2 and 1:1.
Bud – The earliest stage of a new twig with new leaves or flowers. Buds arise at the very end of a twig (terminal bud) or in the axil of a leaf (axillary or lateral bud), or from random places in the bark (dormant buds). A bud is mostly covered by scale-like structures, BUD SCALES; sometimes terminal buds are covered by stipules from the previous leaf. Out of a bud grows a new twig with new leaves, or an axis with flower buds that develop into flowers (flower bud).
Bud scales – The coverings of a bud; usually bud scales drop off when the bud develops, sometimes they remain for some time at the base of the new twig.
Bullate – Surface of the blade prominently raised between the laterals or veins, bulging; also of some seeds with rounded protuberances.
Butt flares – Narrow, steep, mostly high-reaching BUTTRESSES.
Buttress – An often more or less triangular fortification of the base of the tree, sometimes low, sometimes high-reaching, sometimes thick, sometimes plank-like, sometimes narrow, sometimes wide-spreading: a wide variety of forms. Within one species buttress form can vary widely.


Caducous – Falling off early.
Calyx – The outer envelope of adapted (modified) leaves protecting the inner parts of a flower, consisting of free or united SEPALS, usually CADUCOUS but sometimes PERSISTENT on the fruit .
Cambium – The thin, soft, white layer (invisible by the naked eye) of tissue between the wood and the bark. The CELLS of the cambium have the capacity to divide over and over again; the newly formed cells on the inside of this cambium layer will form new WOOD, thus causing diameter growth. The newly formed cells on the outside will form new bark tissue.
Canaliculate – With a longitudinal groove: a grooved petiole, a grooved rachis.
Canopy – The mostly closed and dense layer or cover, formed by the crowns of the tallest trees (canopy trees). It is the top layer of the upper story of the forest; in a fully developed, mature rainforest other layers are: the middle story, the lower story, the shrub layer and the herb layer.
Capitate – Bundled together in dense, head-like flower clusters, like in Parkia and Nauclea.
Capsule – A dry fruit composed of two or more united CARPELS, and either splitting when ripe into pieces called valves, or opening by slits or pores.
Carinate– Keeled, with a distinct ridge.
Carpel – The building stone of an OVARY: a “fruit-leaf” = adapted (modified) leaf carrying the OVULES along its edge. The ovary is the central part of a (female) flower. An ovary can consist of a single carpel, of several separated (free) carpels, or of two or more united carpels. A fertilized ovary develops into a fruit.
Caudate – Abruptly ending in a long tail-like tip or appendage.
Cauliflorous (cauliflory) – Producing flowers and fruits on older stems and or branches, separate from the leaf bearing twigs. See also Ramiflorous.
Cell– The building block of living tissues: a tiny structure, invisible to the naked eye, consisting of a cell wall and cell content. Young cells have the capacity to divide (cell-division), thus enlarging the structure they are part of (CAMBIUM cells); when older they can specialize, forming wood, bark, leaves, etc.
Cell – A cavity in an ovary or a fruit: a 1-celled ovary, 2-celled ovary, a 3-celled or 3-locular fruit, etc.
Ciliate – With a fringe of hairs along the edge.
Cicatrice – The mark or scar left by the separation of one part from another, as from a leaf from a twig, or a bark scale from the bark.
Climber– A mostly woody plant, at least initially with a very thin stem, growing erect by using other objects like shrubs or trees as support and using roots, hooks and tendrils to attach itself.
Cleft – Cut halfway down.
Club-shaped – Gradually thickening upwards from a slender base.
Clustered – When leaves are tightly grouped together at the end of the twig, making it difficult to see if the leaves are ALTERNATE, OPPOSITE, or WHORLED. Both SIMPLE and COMPOUND leaves can be clustered.
Coastal – Pertaining to the coast, growing near the coast.
Coiled – As if a thick rope is wrapped around the base of a stem.
Colleters – Slimy or gum secreting hairs, mostly on leaves.
Compact – Closely joined or pressed together.
Compound – When the BLADE of a leaf is subdivided into several to many smaller units, called LEAFLETS. There are many variations of compound leaves: PINNATE, BIPINNATE, DIGITATE.
Compressed – Of a body: flattened lengthwise from side to side (laterally) or from front to back (dorsally), so that the cross section is not round but ± elliptic.
Concave – Hollow, as the inside of a saucer; a surface curved inwards.
Concentric – Arranged in rings around a common centre, like annual growth rings in a cross cut of a stem.
Connate– When several similar parts are joined so closely together that they cannot be separated without tearing.
Conical – Having the shape of a cone.
Contoured – When the bark is structured in concentric TANGENTIAL layers of a different colour or structure.
Convex – Having a more or less rounded surface, curved outwards.
Copious – Abundant, e.g. abundant latex, copious fruits.
Coppice – A small patch of cultivated forest where the stems of the trees are cut close to the ground at regular distances in time in order to let the remaining stumps form new stems to grow to a certain size, after which they are harvested.
Coppicing – The practice of cutting young stems of trees in order to let the remaining stump grow new stems.
Cordate – When the base of the BLADE is more or less notched, “heart-shaped”.
Coriaceous – When the blade is thick and feels leathery.
Cork/Corky – A soft and waterproof tissue formed by the bark on twigs, branches, stems and roots; sometimes as a continuous layer around the stem, sometimes very local: corky pustules.
Corolla – I ring of adapted (modified) leaves inside the CALYX in a flower, consisting of united or separate, often coloured PETALS – presumably functioning to attract pollinating insects or birds.
Cotelydons – The first pair of often opposite leaves of a seedling, also called seed-leafs, generally totally different from later leaves.
Cream-coloured – White with a slight inclination to yellow.
Crenate – When the margin is shallowly notched with regular blunt or rounded teeth.
Crest – An elevation or ridge at the end or along the side of an organ.
Crowded – Closely pressed together, thickly set.
Cuneate – When the base of the BLADE is wedge-shaped, the blade becoming gradually narrower towards the petiole.
Cuspidate – Abruptly tipped with a sharp point (as caudate but the tip sharp and rigid).
Cylindrical – Elongated with a circular cross-section.


Deciduous – Falling off eventually; loosing its leaves, not evergreen.
Decurrent – When the MARGIN of the BLADE extends down along the PETIOLE, or when the edge of a petiole runs down along the twig.
Decussate – Of opposite leaves: when the successive pairs are at right angle with each other.
Deeply incised – When the incisions in the margin of a blade reach close to the midrib.
Dehiscent – Opening spontaneously when ripe, as capsules, pods.
Deltoid – Shaped like a ± equal-sided triangle.
Dendrology – The study of trees.
Dentate – In general: when the MARGIN of a BLADE is toothed with the points pointing outwards; more specific: when the incisions between the teeth are not sharp but more or less rounded.
Depressed – Of a surface when it is slightly pressed down.
Descending – Bent or curved downwards, as opposed to ascending.
Diagonal – Of a midrib, running from one corner of a more or less rhombic blade to the opposite corner.
Dichotomous – Forking regularly in two; a dichotomous key: where you have to choose between two possibilities.
Dicotyledons (Dicots) – The class of plants (consisting of many families), of which the seedlings have two COTYLEDONS or seed-leaves.
Digitate – When the BLADE is subdivided into more than three more or less equal-sized but separate LEAFLETS, all attached to the top of the PETIOLE. The digitate leaf has no RACHIS; leaflets can be SESSILE or have a usually short PETIOLULE; each leaflet has a distinct MIDRIB. When there are only three leaflets, it is a TRIFOLIOLATE leaf. See also PALMATE.
Dilatation tissue – Mostly vertical strips or bands of often lighter coloured and softer structured tissue in the BARK; dilatation tissue is new tissue, formed inside the bark (and usually inside the BARK RAYS) in order to keep up with the circumference (TANGENTIAL) growth of the tree.
Dioeceous – With the flowers only being male or female (unisexual), and on separate individual plants, as opposed to MONOECIOUS, where male and female flowers appear on the same plant.
Dispersal – The various ways by which seeds are scattered, by wind, by force, by being eaten, by sticking to animals etc.
Dissected – Deeply divided or cut into many narrow segments.
Dictichous – Two-ranked. When ALTERNATE, SIMPLE leaves are placed at a regular distance along the TWIG, alternating left-right-left-right. Often a tree has distichous leaves along horizontally spreading twigs, the leaves on ascending branches being more spirally arranged. Opposite, simple leaves can also be distichous.
Domatia – Tufts of hairs, small pits or other fine structures in axils of laterals or finer veins; sometimes clearly visible, sometimes a magnifying glass is needed; mostly visible on the underside of the blade, but sometimes visible as a spot on the upper surface.
Dormant – Mostly applied to buds that are hidden in the bark or a leaf axil and not active.
Drip tip – The abruptly narrowing long acuminate tip of a leaf or leaflet, from which water drips down.
Drooping – Bent downwards but not quite hanging down.
Drupe – A fruit consisting of a fleshy or leathery outer layer, containing usually only one “stone” with a kernel (e.g. a mango).


Echinate – Covered with prickles.
Edaphic – Related to or caused by particular soil conditions.
Edge – Of a leaf: its margin.
Ellipsoid – Of a fruit: elliptic when cut lengthwise.
Elliptic – Shaped like an ellipse, a rounded figure with the widest part in the middle and the length:width ratio of 5 : 2 – 3 : 2.
Elongate – Drawn out in length.
Emarginate – When the usually OBTUSE tip of the BLADE is shallowly notched.
Endemic – Confined to a certain region or country and not native anywhere else.
Endocarp – The innermost layer of the wall of the fruit (PERICARP) surrounding the seeds.
Entire – Of a blade: “entire” means the blade is not more or less deeply incised, although the margin itself may show different forms of SERRATIONS; of a margin: when it is even, without teeth, lobes, etc.
Epicotyl – The section of a seedling above the first pair of leaves (COTYLEDONS) and the next leaf.
Epidermis – The outermost layer of cells of an organ, its “skin”; usually only one cell thick.
Epiphyte – A plant which grows on another plant but not tapping the host for food, not parasitic; many Ficus species are, or start as epiphytes.
Equal-sided– When both halves of e.g. a blade or a fruit are equal in shape, but mirroring.
Erect – Upright.
Estipulate – Without stipules.
Evergreen – Bearing green foliage all the year.
Excentric – Out of the centre.
Excrescence – An outgrowth or wart on the stem or branch.
Exocarp – The outermost layer of the fruit wall, like a skin.
Exotic – Not native, introduced from another country or continent.
Exudate – Any liquid or gelatinous or resinous substance emerging from a slash wound – or any wound.


Falcate – Curved like a sickle or scythe; of a leaf: the midrib curved.
Family – In botany: a group of related genera.
Ferruginous – Rust-coloured.
Fibrous – Showing much woody fibre, like the outside of a coconut.
Fid – When a blade is deeply incised past halfway the midrib. Pinnati-fid when so in a penni-nerved blade; palmati-fid when so in a palmate blade.
Fiddle-shaped – In the form of a violin.
Filiform – Literally: thread-shaped; long and thin, nearly like a needle.
Fissured – A bark with many fine, vertical, ± parallel grooves or cracks.
Flaky – A bark with many very thin bark scales.
Fleshy – Thick, firm, yet soft and easily sliced.
Flower – An assemblage of organs (adapted leaves) that together form the reproductive organ of a plant. A complete flower has a calyx (protective structure), a corolla (attractive structure), the stamens (male organs), and the ovary (female organ), all inserted on the receptacle.
Fluted – Of a stem with high reaching, narrow and thin flares and ridges.
Folded leaf – When the two halves of a blade are not ± flat in one plane but (closely) angled towards each other.
Foliaceous – Leaf-like.
Foot – An American measure of length: 1 foot or 1′ = 12 inches or 12″; 1 foot (plural = feet) is 30.5 cm.
Fruit – A body that develops from a fertilized OVARY, containing seeds; often fruits provide the mechanism to spread the seeds: woolly hairs for wind distribution, opening with force to throw out the seeds, being edible etc.


Gall – An unusual, often rounded growth on a leaf or a twig, caused by an insect puncture.
Gallery Forest – Usually narrow strips of high forest along rivers in a savanna region.
Gelatinous – Jelly like.
Genus – In botany: a group of narrowly related species that all carry a common genus name; plural: genera. A genus sometimes includes only one species (e.g. Polystemonanthus dinklagei) or many species (like Albizia).
Germination – When a seed starts growing, first forming a root, followed by the first stem structure with leaves: HYPOCOTYL + COTELYDONS.
Glabrescent – Becoming glabrous or nearly so.
Glabrous – Without hairs or appearing to be so.
Gland – A (sometimes very) small structure on the margin, surface, or imbedded in the BLADE, on the PETIOLE, or raised on a small stalk (glandular hairs or stipitate glands), sometimes secreting a liquid that may attract insects.
Glaucous – With a bluish/greenish colour or hue due to a thin waxy coating.
Globose – Nearly spherical (globular).
Glomerate – Compactly clustered or pressed together.
Glossy – Shining, polished.
Granular – Of the bark: grainy, composed of small grains – as opposed to fibrous.
Green layer – An often very thin outer layer of the living bark, between the living inner and dead outer bark.
Gregarious – Growing in company, in groups of the same species.
Grooved – A bark with deep and wide vertical, ± parallel grooves.
Grit, gritted– Of a bark: with small, sand-like particles, making a metallic sound when slashed.
Gum – A sometimes sticky, thick liquid exuding from a wound in a stem, hardening in the air.


Habit– The general appearance of a whole plant, like tree, or liana; the whole tree or its crown.
Habitat – The kind of environment where a tree grows, high forest, as swamps, river borders, savanna etc.
Hair – An outgrowth of the outer layer (EPIDERMIS) of a twig or leaf: an elongated cell of several aligned cells.
Heart shaped – When the base of a blade has two rounded lobes; cordate.
Heartwood – The innermost, oldest, and dead wood in the middle of the stem, often different in colour from the still living outer layer of the stem (the SAPWOOD).
Herbaceous – Not woody, often green in colour.
Hirsute – PUBESCENT or hairy with rather coarse and tiff hairs, covering the surface.
Hoop – On the bark: a narrow circle of distinct structure or texture running around the stem.
Horizontal – In general: parallel to the horizon. Stem: with ridges at right angles with axis of the tree. Branches: spreading out horizontally.
Hypocotyl – The stem of a seedling between the seed and the first pair of often opposite leaves (COTYLEDONS) that are usually differently shaped from the next leaves; see also EPICOTYL.
Hypogeal -When at germination the hypocotyl does not develop and the seed remains on or in the ground.


Impari-pinnate – Similar to a PINNATE leaf but with one leaflet (or odd leaflet) at the end of the RACHIS; also used is the term oddly pinnate.
Impressed – Of laterals and/or veins that are not flush with the blade surface but form a narrow groove in the surface.
Inch – A measure if length used in the United States of America; 1 inch (1″) = 2.54 cm = 25.4 mm.
Incised – In general when the blade of a leaf shows more or less deep incisions between some of the LATERALS; there are three degrees of division: -fid, when the incision goes to about 1/4 of the length of the laterals; -lobed, when the incision goes from 1/4 – 3/4 of the length of the laterals; -partite when the incision nearly reaches the base of the laterals. Some leaves have a pinnate VENATION, hence such a simple leaf can be: ENTIRE, PINNATI-FID, PINNATI-LOBED, or PINNATI-PARTITE. Some leaves have a PALMATE venation, hence such a leaf can be: ENTIRE, PALMATI-FID, PALMATI-LOBED, or PALMATI-PARTITE.
Inconspicuous – Not easily seen because of its small size or lack of colour.
Indehiscent – Of fruits: not opening when ripe.
Indigenous – Originally found in this country, not introduced from elsewhere.
Indistinct – When structures (like laterals, or venation) is not clearly visible.
Indumentum – Any covering such like hairs or scales.
Inermous – Without spines of prickles, UNARMED.
Inflorescence (axial, axillary) – The arrangement of the flowers on a plant.
Infructescence – The arrangement of the fruits on a plant; an inflorescence turns into an infructescence when fruits ripen.
Inserted – Joined to or placed on
Intermediate – Half-way or between.
Internode – The section of a branch or a twig between two NODES.
Interpetiolar – Of stipules, when placed at the NODES between the petioles of opposite leaves; interpetiolar stipules are often joined together (connate).
Intramarginal – Just inside the margin of a blade.
Intrapetiolar – Of stipules, when placed at the NODES in between the petiole and the twig, in the axil of a leaf; intrapetiolar stipules are joined together (connate) along one margin.
Involute – When the margin of a blade is rolled inwards.


Joint – The often swollen and wrinkled (RUGOSE) place at the base or the top of a petiole or petiolule which enables the leaf or leaflet to adjust its orientation, e.g. its exposure to light, or sleep movements at night.
Jugum/juga – A pair of (sub-)opposite leaflets of a PINNATE leaf; the plural of jugum is juga. An IMPARI-PINNATE leaf has e.g. 3 juga (or three pairs of leaflets) and an odd leaflet.
Juvenile – A young stage in the life cycle of a plant; juvenile leaves are often rather different from mature leaves.


Kapok – The woolly fibre tissue surrounding the seeds of many species of the Bombacaceae family, like in Ceiba: Cotton tree.
Knee roots – Roots that rise out of the soil or water and bend back into the soil/water; usually in swamps.


Laciniate – Split up into fine, slender lobes or strips.
Lamina – The BLADE of a leaf or leaflet.
Lanceolate – Long and narrow, 3 – 6 times as long as broad, with ± parallel edges or broadest below the middle.
Lateral – The first branching of the MIDRIB of a PENNI-NERVED simple leaf or LEAFLET; in PALMATI-NERVED leaves laterals are the first branching of the primary or BASAL NERVES.
Lateral – Laterals show identifying characteristics like: straight, curved, looping, reaching the margin or not.
Lateral – The number of laterals is often characteristic: few, normal, many, numerous, distinct, indistinct.
Latex – The milky juice exuding from a slash of such plants as the rubber tree. Latex can be white, opaque, yellow, orange, sticky.
Lax – Loose, with wide spaces in between
Leaf – An expanded, usually green organ or structure of plants, serving to receive and use sunlight energy to form organic molecules of sugar and starch from water and carbon dioxide: photosynthesis. In woody plants leaves are born along branches and twigs; the place of attachment is a NODE. Leaves show two important, easily seen characteristics that are helpful for identification: 1. their arrangement along the twig: ALTERNATE, in two rows or DISTICHOUS, OPPOSITE, in WHORLS, or CLUSTERED; 2. their shape: SIMPLE or COMPOUND.
Leaf – A simple leaf consists of: 1. STIPULES (present or not); 2. A leaf stalk or PETIOLE; when the petiole is absent the leaf is SESSILE. 3. The expanded part, BLADE or LAMINA. Major parts of the blade are: the BASE, the MARGIN, the tip or APEX, the MIDRIB, the LATERALS. Detail characteristics are: hairs or PUBESCENCE, GLANDS, DOMATIA, VEINS. In a compound leaf the separate sections of the blade are called LEAFLETS, their stalks are PETIOLULES; they are arranged along an extension of the PETIOLE, the RACHIS.
Leaf– A compound leaf can lack an extension of the PETIOLE, in which case we speak of a DIGITATE leaf, all LEAFLETS coming together at the top of the petiole. Or there can be a longer or shorter extension of the petiole, the RACHIS, along which the leaflets are arranged: a PINNATE leaf. However, when the leaflets themselves are again subdivided into smaller units, the leaf is BIPINNATE, with a primary rachis and secondary rachises.
Leaf – A bipinnate leaf is like a pinnate leaf but each leaflet has been subdivided again into a secondary rachis with leaflets. Secondary rachis + leaflets together form a PINNA (plural: pinnae). Some species lack a rachis: there is only one pair of pinnae.
Leaflet – The separate divisions in which a compound leaf is subdivided, the leafy parts of a compound leaf. Each leaflet may resemble a leaf with a PETIOLULE. Leaflets can be very small – medium-sized, rarely big.
Lenticel – Small, often corky structures on the bark, corresponding with underlying BARK RAYS and WOOD RAYS; lenticels are like small breathing holes, allowing the inner layers of bark and wood to get oxygen. They are often scattered, but also in vertical or horizontal rows.
Lenticellate – Having LENTICELS.
Liana – A climbing, woody plant.
Lignified – Having become woody, converted into wood.
Linear – Long and narrow, with parallel edges; length:width ratio ± 12:1.
Lobed – Incisions of the blade reaching about halfway along the LATERALS, see also INCISED.
Locular – Having compartments, cells, or cavities; uni-locular: having only one compartment or cell; bi-locular: having two cells.
Long petiole – When a petiole is more than 4 cm long.
Longitudinal – In the direction of the length.
Looping – Of the laterals, when they connect near the margin with distinct arches.


Mangrove – A forest type on muddy shores bordering salt water, composed of a limited number of “mangrove species”, most notably Rhizophora species and Avicennia.
Margin – The edge of the blade. It can be ENTIRE: without SERRATIONS, or with serrations. It can be DECURRENT, when the blade margin extends down along the PETIOLE.
Marginal – Situated on the margin, like marginal glands. Marginal nerve: The edge of the blade is a nerve to which the laterals connect; sub-marginal nerve: this nerve lies just within the edge of the blade.
Marginate – Broad-rimmed, having a margin of distinct character.
Membraneous – Thin and semi-transparent, like a membrane; often thin, soft, and flexible.
Mericarp – Portion of the total fruit which splits away as a separate, perfect fruit, as a rule formed by a single carpel.
Mesocarp – The often fleshy, succulent, or fibrous body of a fruit between the outer skin and the seed(s).
Midrib – The central axis of the BLADE (leaf and leaflet), the extension of the petiole in the blade, dividing the blade in two more or less equal halves.
Monocotyledon – A plant belonging to the taxon of those plants that have only one seed-leaf or COTYLEDON; leaves usually with parallel veins: grasses, orchids, palms.
Monoecious – When flowers are either male or female, but both occur on the same plant; see also dioecious.
Montane – Ending abruptly in a short (stiff) point.
Mucous – Slimy.
Mucro – A short, often sharp terminal point.
Mucronate – Ending abruptly in a short (stiff) point.
Muricate – Rough, with short and hard excrescences.
Myrmicodomous – Affording shelter to ants, e.g. ants living in hollow twigs.


Narrowly – Expressing that the length:width ratio of a flat surface (e.g. a blade) varies between 6 : 1 and 3 : 1; narrowly elliptic, narrowly ovate, etc.
Nectar – A sweet fluid exuding from various parts of a plant, e.g. from glands; from flowers it is called honey.
Nervation – The manner in which the nerves or LATERALS are arranged in a blade.
Nerves – Another word for LATERALS.
Net-veined – The veins in the blade forming a distinct network.
Node – The point on a stem or a branch or a twig at which a branch or a twig or leaf is attached.
Nomenclature – The correct use of scientific names in TAXONOMY.
Normal petiole – A petiole of 12 – 40 mm long.
Numerous – Many, not readily counted.
Nut – A 1-seeded INDEHISCENT fruit, with a hard and dry PERICARP (the shell).


Oblanceolate – Long and narrow like LANCEOLATE, but with the broadest part above the middle.
Oblique – When the two sides of a blade are unequal at the base, slanting, unequal-sided.
Oblong – Much longer than wide, the sides nearly parallel; length : width ratio between 5:2 and 3:2.
Obovate – OVATE but the widest part above the middle; length : width ratio between 5:2 and 3:2.
Obscure – Not clearly visible, or visible with a lens only.
Obtuse – Blunt or rounded at the end.
Oddly pinnate – Another word for IMPARI-PINNATE.
Opaque – Not transparent, but letting some light through; dull, not shining.
Opposite – When two leaves are attached at the same NODE, opposite of each other.
Opposite – When two branches are attached at the same height and on either side of the stem.
Orbicular – Flat with a more or less circular outline.
Oval – Elliptical, the widest part in the middle.
Ovary – The central part of a flower, enclosing the OVULES; it is the female organ of a plant. An ovary can consist of a single, folded CARPEL, of several separate carpels (as in Annonaceae and Sterculiaceae), or several carpels joined along the edges. After POLLINATION the ovary develops into the FRUIT.
Ovate – Egg-shaped but flat, the widest part below the middle; length : width ratio between 5:2 and 3:2.
Ovoid – 3-dimensionally egg-shaped.
Ovule – The female egg in plants that need to be fertilized by POLLEN to develop into a FRUIT. Ovules develop in a CARPEL and are attached to the wall of the carpel.
Oyster shell – More or less concentric markings on the bark as a result of shedding bark scales.


Paired – In couples or pairs.
Palmate – Of a BLADE, lobed or divided into segments like the palm of a hand, but the segments not separate: it is a simple leaf! Each lobe with its own midrib. See also DIGITATE.
Palmati-nerved – When several nerves (more than 3) spread from the base of the blade in a palmate manner, like the fingers of a hand.
Palmati-sect – Palmately divided almost down to the base of the blade, nearly digitate.
Papilionaceous – Occurring in or belonging to the family of Papilionaceae.
Papillose – Covered with small, nipple-like protuberances.
Pari-pinnate – A PINNATE leaf with an even number of (sub-)opposite leaflets, the terminal leaflet missing (see also IMPARI-PINNATE).
Partite – Incised or cleft nearly but not entirely to the base.
Pedicel – The stalk of each individual flower.
Peduncle – General name for the stalk of a flower, a bunch of flowers, a fruit, or a bunch of fruits.
Peelable – Of the bark, when it is easily stripped off in narrow, thin strips or layers; common in many Annonaceae.
Pellucid – Translucent, e.g. pellucid points = translucent points.
Peltate – when the stalk (petiole) of a leaf is attached to the underside of the leaf instead of at its base
Pendulous – Hanging down.
Pericarp – The wall of a fruit, enclosing the seed; it may be formed by one layer, or by three more or less distinct layers: EXOCARP (outer layer), MESOCARP (middle layer), and ENDOCARP (inner layer).
Perpendicular – Used of a structure with its direction vertical to the horizon or at right angles with its attachment.
Persistent – Remaining attached to the part which bears it, at least till it is matured.
Petal – One of the often coloured, leafy organs surrounding the ovary in a flower.
Petiolate – Having a petiole.
Petiole – The stalk of a leaf, the connection between the twig and the BLADE. All leaves, both simple and compound, have a petiole, unless it is absent: a SESSILE leaf. In the Tree Atlas petioles are categorized as: SESSILE, there is no distinct petiole; SHORT, 1 – 12 mm long; NORMAL, 12 – 40 mm long; LONG, more than 40 mm (4 cm) long.
Petiole – A petiole can have many identifying characteristics, like having a swollen BASE, the base forming a JOINT, the top forming a joint, it being round on cross section, or flattened above, or ribbed, or winged; the petiole can have (usually only one) GLAND on its upper surface; it can be GLABROUS or PUBESCENT; it can have THORNS; sometimes the MARGIN of the BLADE extends along the petiole: DECURRENT.
Petiolule – The petiole of a LEAFLET; petiolules are usually very short.
Pilose – Hairy with rather long, simple hairs.
Pinna – When a leaflet of a PINNATE leaf has itself been subdivided again; in a bipinnate leaf a pinna equals a secondary rachis with the leaflets attached to it. The plural of pinna is pinnae. Pinnae of a bipinnate leaf are opposite or sub-opposite, rarely truly alternate; leaflets along the secondary rachis can be opposite or alternate.
Pinnate – When the blade of a leaf is subdivided into several to many smaller units, called LEAFLETS, arranged along a common axis, the rachis. The leaflets can be OPPOSITE, SUB-OPPOSITE or ALTERNATE.
Pioneer – Plants that invade recently cut or disturbed forest land or forest edges; usually fast growing light-demanding species.
Pith – The spongy centre of a twig or stem, often white, sometimes brown; sometimes ladder-shaped.
Pitted – Marked with small depressions.
Pneumatophore – Branches of the roots that extend vertically above the mud or the water, serving as lungs for the roots in the oxygen-depleted environment of swamps and mud flats.
Pod – The most common type of fruit in the Leguminosae family = Bean family. The fruit is formed by one, folded carpel and has the seeds aligned in one line. Pods are usually dry and flat, opening along one or two seams. Some Leguminous fruits look quite different, however.
Pollarding – The practice of cutting off the top of a young tree at a certain height, e.g. 1.80 m, with the purpose of letting the stem form new shoots that can be harvested in following years. The practice of pollarding is similar to COPPICING, but the place where the new shoots grow is much higher above the ground. The reason is that dense undergrowth will not compete for light with the new shoots; also, livestock cannot browse the fresh shoots. Pollarding is done to produce certain products, like fodder for livestock (thin shoots, short harvesting cycle), fire wood, construction stakes. A pollarded tree is called a POLLARD.
Pollen – The dust-like, often yellow, often sticky sperm cells produced by the male flowers that can fertilize the female flowers.
Pollination – The placing of the POLLEN on the STIGMA of a flower: fertilization; pollen can be distributed by wind, insects, bats, etc.
Poly – In compounds: the Greek word for many. Polycarpa = with many fruits.
Prickle – Usually sharp structures on the outside of the bark, not connected to the underlying wood. A prickle is an outgrowth of the bark or skin of a twig, petiole, or fruit; it can usually be broken off without damaging the underlying tissues. The term THORN is used for both SPINES and prickles.
Prickly – Having prickles.
Procumbent – Bent over, trailing, and spreading along the ground.
Prominent – Standing out, raised above surrounding surface: prominent laterals in a blade, prominent ridges on a fruit etc.
Prop roots – Roots growing ± downwards from branches or the lower stem.
Pseudo stipules – “False” stipules but actually the lowest pair of leaflets of a pinnate leaf which may resemble stipules, embracing the twig.
Puberulous – Shortly or sparely pubescent with very short, erect hairs difficult to feel.
Pubescence – The hairiness of a plant.
Pubescent – Covered (but not densely) with short, soft hairs.
Pulp – The juicy or fleshy inside of a fruit, embedding the seeds.
Pulvinate – When the base or the top of a petiole is swollen, that swelling often serving as a joint, enabling the leaf to shift exposure to light.
Punctate – Spotted with glands or translucent dots.
Pustulate – Having little raised bumps like pimples or blisters or little warts.


Quadrangular – With four corners.


Rachis – The extension of the PETIOLE in a PINNATE or BIPINNATE leaf, along which the LEAFLETS or PINNAE are born. A rachis can show identifying characteristics, like glands, prickles, being winged, angular, grooved, flattened above, ZIGZAG.
Radial – Radiating as from a centre, like the spokes of a wheel; wood rays radiate from the center of the tree.
Ramiflorous, Ramiflory – when the flowers are born between the leaves or on the twigs just below the leaves.
Recurved – Bent backwards, e.g. the margin of a blade.
Radial – Radiating as from a center, like the spokes of a wheel; wood rays radiate from the center of the tree.
Reflexed – Abruptly bent or curved downwards or backwards.
Reniform – Kidney-shaped.
Resin – An exudate from the bark, often sticky, transparent, often aromatic, sometimes solidifying, sometimes flammable.
Resin duct – Thin, often wavy channels in the blade between the laterals or crossing the laterals. In many Guttiferae species.
Reticulate – Net-veined, when the smallest veins are connected like the meshes of a net.
Reticulation – The structure of the veins.
Retuse – Notched (of the tip of a leaf); see: EMARGINATE.
Revolute – Of a blade, with the margin being rolled up inwards.
Rhombic – With the shape of an oblique-angled parallelogram with only the opposite sides equal; in a blade the midrib often running diagonally from one corner to the opposite corner.
Ribbed – Having ribs: twigs, fruits.
Ring scars – Scars at the nodes of twigs where a stipule, covering the terminal bud, had fallen off.
Riparian – Pertaining to the zone along rivers and creeks; often this zone can be flooded during flash rains.
Ripple marks – Ripple marks are very fine, straight or wavy ± horizontal lines visible in a TANGENTIAL section of the bark or wood, especially the inner layers of the SLASH, or the wood; they are the result of the elements forming the wood and the bark being arranged in ± horizontal layers, resulting in a ± horizontally layered structure of wood and bark.
Root spurs – Low support structures at the base of the tree, often shaped like very small buttresses, extending into mostly underground spreading roots.
Rounded – When the edge of a flat surface forms a smooth arc.
Rosette – A cluster of tightly packet spreading leaves.
Rugose – The wrinkled texture of a petiole, petiolule, or joint.


Sagittate – Of the base of a BLADE when it has two acute straight lobes pointing downwards.
Sapling – A young tree, the next stage after SEEDLING.
Sapwood – The outer layer of the woody stem, just under the CAMBIUM by which it is formed; the upward stream of water in the tree flows through the thin channels (vessels) in the sapwood. Sapwood is partially built from still living cells that store food; once these cells die the sapwood usually takes on a different colour and becomes HEARTWOOD.
Sarmentose – With long, flexible, slender branches.
Savannah – A vegetation type dominated by grasses, often exposed to seasonal fires; sometimes with scattered trees (tree-savannah) or patches of forest (woodland savannah).
Scabrid – Rough to the touch, usually from the presence of very short, harsh hairs.
Scalariform – When the veins between laterals are closely arranged ± parallel to each other and ± perpendicular to the laterals. Lax scalariform: when the veins are fairly far away from each other. TRAVERSE scalariform when the veins are ± perpendicular to the MIDRIB.
Scale – 1) a form of hair shaped like a tiny mushroom, with a short stalk and a spread-out top; 2) very reduced (and often not recognizable as such) leaf, often serving as a protective organ, like bud-scales; 3) thin sections of the outer bark.
Scaly – Of bark: having scales on the outside of the bark.
Scandent – Climbing upwards.
Scar – A mark left on a twig where a leaf or stipule has fallen off.
Scattered – Without apparent order.
Secondary formation – Young forest that grows up where the original high forest has vanished, either by harvesting, agriculture, or storm. Its composition is very different from the original high forest, with predominantly light demanding and fast growing species.
Secondary rachis – The common axis of the PINNA of a bipinnate leaf, to which the leaflets are attached.
Section – A group of closely related SPECIES within a GENUS.
Seed – The (often) little bodies inside a fruit from which a seedling can grow.
Seedling – The young plant that arises from a seed. The first pair of leaves, usually opposite, often are very different in form from mature leaves.
Semi-deciduous – Of forest: the forest type between the rain forest and the truly deciduous (shedding its leaves) forest. Many species but not all lose their leaves in the dry season.
Sepal – An often green, more or less leaf-like organ that forms the outer whorl of a flower. Sometimes sepals persist attached to the fruit.
Septate – Divided by one or more partitions.
Septicidal – When a ripe capsule splits into valves along the junction of the carpels, each valve thus being one carpel that itself may split as well.
Sericeous – Silky, with closely oppressed, long, soft straight hairs.
Serrate – When the margin of the BLADE is toothed like a saw, the teeth usually pointing forwards and the incisions (of a few mm deep) being sharp; when the incisions are blunt or rounded: see DENTATE; when the teeth are rounded but the incisions sharp, see CRENATE.
Serration – Various forms of shallow incisions of the MARGIN of a BLADE. When serrations are absent, the margin is ENTIRE.
Sessile – Without a stalk; in a leaf: without a petiole.
Shoot – A young branch or twig that is still growing.
Shrub – A low woody plant, usually with several stems, mostly not exceeding 5 cm Ø
Simple – When the blade of a leaf is one, undivided unit – although it may be LOBED in various degrees; the opposite of simple is COMPOUND.
Sinuate – When the margin is uneven, wavy with rather deep undulations.
Sinuous – When a stem is not straight but curved in various directions.
Slash – The downward cut into the bark, made with a machete, exposing the characteristics of the inner bark: colour, structure, smell, taste, exudates, sound, ripple marks, dilatation tissue. A slash is usually reaching the outer wood layer, showing the colour of the SAPWOOD.
Species – In plants: the basic unit of classification, the collection of all those individual plants which have the same constant and distinctive characters. A species has a double scientific name: the genus name and the specific name, like Tetraberlinia (genus name) tubmaniana(specific name).
Specimen – A dried plant or part thereof, prepared for botanical study.
Spherical – More or less globular in form.
Spine – Usually sharp structure on stems and branches, arising from the underlying wood. A spine is basically a mini form of a twig; it can occasionally grow buds and new side-twigs; it cannot be broken off without damaging the underlying woody tissue; different from PRICKLES, that arise from the bark. The term THORN is used for both spines and prickles. The margin of a leaf can be called spiny when the teeth are hard and sharp.
Stalk – A slender supporting or connecting part, e.g. the stalk of a fruit.
Stamens – The male sexual organ in a flower, producing pollen.
Stellate hairs – Branched hairs with several arms radiating horizontally.
Sterile – When the sexual organs are not functioning, barren; also: a sample without flowers or fruits.
Stigma – The end of the female organ of a flower receiving the POLLEN.
Stiltroots – The oblique or arched adventitious roots at the lower part of the stem above the ground; stilt roots can be low, medium, or high reaching. They can be slim and slender, thick and sturdy, flattened, plank-like.
Stipels – Stipule-like, mostly needle-shaped structures at the base of leaflets of a pinnate leaf (Mimosoideae sub-family)
Stipitate – Supported on a short stalk.
Stipule (Stipulate) – Leaf-like, scale-like, or needle-like appendages of a leaf, usually at the node or base of the petiole; stipules are totally absent in a number of species (or even families), present only on the very young developing twigs but soon falling of (caducous), or remaining for a longer period at the base of the petiole (persistent). They can be INTERPETIOLAR (most commonly in Rubiaceae species), INTRAPETIOLAR, or just at the base of the petiole. Sometimes stipules cover the terminal bud and fall off when the bud develops, leaving a circular SCAR at the node. STIPULATE: Having stipules.
Straggling – With an irregular habit, partly trailing, partly growing upwards.
Striate – Marked with parallel, horizontal or longitudinal lines, grooves or ridges.
Sub – A prefix meaning “somewhat”, or “slightly”: sub-acute = somewhat acute; sub-opposite: nearly but not quite opposite.
Sub-family – A group of related genera within a family.
Sub-marginal – A vein running close to and ± parallel to the margin of a blade.
Sub-opposite – When the leaflets of a PINNATE leaf are not arranged exactly in opposite pairs but two leaflets of a pair being slightly off-set to each other. Or when leaves are not quite opposite along the twig.
Subulate – Tapering evenly from a narrow base into a fine point; awl-shaped.
Succulent – Thick, fleshy and often juicy.
Suckers – New shoots arising from a root or the base of a tree.
Sulcate – With longitudinal grooves.
Suture – The line of junction or seam where carpels grow together, usually the line along which a fruit opens
Symmetric – When one half of structure (a leaf, a fruit) is equal in size and shape like the other half, but mirrored.
Synonym – A previously used but no longer valid botanical name of a plant, like Heritiera utilis (Wishmore) used to be named Tarrietia utilis.
Swollen – When part of a structure (stem, petiole) is thicker than the rest: swollen base of tree, of petiole.


Tangential – When a slice of the tree is taken parallel to the outer surface, e.g. a SLASH; see also: CROSS SECTION and RADIAL SECTION.
Taxon (Taxonomy) – A natural group of plants, like a species, or genus, or family; plural: taxa. Taxonomy: the scientific discipline dealing with the classification of plants or animals.
Terete – Cylindrical, round, circular in cross-section.
Terminal – Positioned at the end of an axis, like the end of a twig (terminal bud, terminal inflorescence) or the end of a rachis (terminal leaflet).
Thorn – Any sharp-pointed structure on stems, branches, leaves; ‘thorn’ includes both SPINE and PRICKLE.
Three-lobed – When the blade is divided into three sections, the incisions going about halfway the midrib.
Three-locular – When a fruit has 3 cells or cavities.
Three-nerved – When three strong nerves arise (close) from the base of the BLADE. Usually the middle nerve is the most prominent, being the RHACHIS; sometimes the three nerves are ± equally strong: a palmate leaf with only three basal nerves).
Tomentellous – Tomentose with very short hairs.
Tomentose – Densely covered with short and soft hairs, ± matted.
Translucent – Of cells or small structures in the BLADE that let through light when held against a source of light.
Transparent – Letting light shine through, like transparent or clear exudates.
Transverse – Of structures on the bark (ridges, lines of LENTICELS) or in the BLADE (nerves), running perpendicular to the edge or axis. Transverse SCALARIFORM: when the veins are perpendicular to the MIDRIB rather than the LATERALS.
Transversely – Expressing that a flat surface, e.g. a blade, is wider than long, the width:length ratio between 3:2 to 5:2.
Tree – A woody plant having a permanently woody main stem or TRUNK (usually only one), normally growing to considerable height and usually developing branches at some distance from the ground.
Treelet – A very small tree is called a Treelet.
Tri-foliolate – A compound leaf with three leaflets, either digitate (when all three leaflets are ± equal) or pinnate with only one pair of leaflets and a terminal one – in which case there is a rachis forming the stalk of the middle leaflet.
Tri-nerved – See three-nerved.
Twisted – When a petiole or petiolule makes a corkscrew twist.


Unarmed – Without any thorns, prickles, or spines.
Undulate – When the MARGIN of the BLADE is not flat but shows a wavy pattern up and down.
Unequal-sided – When both halves of the base of the BLADE are shaped differently. See also ASYMMETRIC.
Unilocular – Consisting of one cell only.
Unisexual – Of a flower, being either female (with ovary) or male (with stamens).
Urceolate – Urn-shaped, with a short swollen neck, contracted near the top and then slightly expanded.


Valve – One of the parts produced by the splitting of a ripe fruit.
Vegetative – Part of a plant without reproductive organs, flowers/fruits; e.g. a twig with only leaves.
Veins – The fine branching of the LATERALS or nerves; strands of vascular tissue in the blade or on the surface of fruits. See also VENATION.
Velutinous– Densely covered with soft, short and/or long hairs; velvety.
Venation – The network of secondary and tertiary VEINS in the blade, usually better visible on the underside than on the upper side of the blade. Venation can be very open or LAX, ‘normal’, or dense. A special form of venation is SCALARIFORM.
Verticillate – See WHORLED.
Villous – Covered with long, weak, and often crooked hairs.


Wart – A hard and firm excrescence or pustule.
Wavy – Not flat, but like a water surface with shallow waves; also: the edge of a flat blade with smooth shallow curves: UNDULATE.
Whorl/Whorled – When more than two leaves are attached at the same NODE; or when a number of branches are extending from the stem at the same height, arranged regularly around the stem; verticillate.
Wing – A usually thin and membranous, flat expansion of the edge of the winged object: a winged TWIG, or PETIOLE, or RACHIS, or FRUIT, or SEED.
Wood – The material inside the bark that the stem and the branches are made of; it is a tissue, formed by the CAMBIUM and consists of vessels (for water transport), parenchyma (for storage of food) and fibres (for strength). These elements have a length-wise orientation and are interwoven with the horizontal elements of the WOOD RAYS.
Wood ray – Structures in the wood with a horizontal/radial direction. They are formed by the CAMBIUM and are clearly visible on the cross section of the stem as thin lines connecting the outside of the stem with the inside, like the spokes of a wheel. In the TANGENTIAL cut of a stem they are visible as lens-shaped spots in the wood. On the RADIAL cut of a stem they are visible at narrow bands at right angle with the wood fibres. Wood rays serve as transport channels for food and oxygen from the inside of the bark to deeper layers in the wood.


Xylem – Another word for WOOD.


Yellow latex – Yellow EXUDATE common in many species of the Guttiferae family.
Yellow slash – When the slash has a more or less bright yellow colour.


Zigzag – When the direction of the twig or stem changes at every node, from side to side: left, right, left, right etc.