Leaf Features

General Leaf Features

Leaves (position on branchlet)

clustered at end of branches with internodes indistinct	spaced along branches with internodes readily visible

Note: Although most trees tend to have the leaves inserted towards the end of the branchlets, the main difference between the two categories of this feature is whether or not the internode (part of the branchlet between the bases of the leaves) is clearly visible or not.

Leaves (insertion/arrangement)

opposite (in pairs, opposite one another on the branch)	whorled (with more than two leaves inserted at one node of a branch; arising from one level)	spiral (leaves occurring singly at a node/level and arranged spirally up the branch)

Note: the leaf arrangements of ‘opposite and all leaves in one plane’ and ‘opposite and decussate – leaves in two planes’ are not distinguished in this Guide to Trees of Papua New Guinea. Both are treated as ‘opposite’. Likewise, ‘spiral’ is here used to include ‘spiral – leaves in at least two planes', and ‘alternate and leaves in one plane’.

Leaves per whorl

Leaves simple or compound

simple (each leaf composed of a single lamina/blade)	compound (each leaf made up from two or more leaflets)

Note: Compound leaves which consist of only one leaflet (unifoliate compound leaves), are frequently difficult to distinguish from simple leaves, except by careful examination. Unifoliate leaves are also scored as ‘simple leaves’ so that these species will not be excluded from the identification key even when this feature is interpreted incorrectly.

Petiole presence

absent	present

Petiole wing

not winged	winged

Petiole attachment to lamina

attached to surface of leaf lamina (hence, peltate)	attached to base of leaf lamina (hence, not peltate) Note: this is the most common form of petiole attachment to the leaf lamina (blade)

Petiole swollen at either end

not swollen more or less the same diameter/width throughout	swollen at tip, or base, or both. The 'tip' of the petiole refers to the point of attachment with the lamina, whereas the 'base' refers to the point where the petiole is attached to the branchlet (twig).

Leaves lower surface colour

Leaves upper surface colour

Leaves indumentum (hairs) presence

Leaves indumentum (hairs) density

Leaves gland-dotted

This feature is recorded as: absent, or present

Leaves domatia presence

It can have the values: absent, or present

Leaves domatia distribution

Leaves lamina shape

broadest above middle - equivalent to oblanceolate, obovate, spathulate, and other similar shapes that are broadest towards the apex of the leaf	broadest at or near middle - equivalent to elliptic, oval, and other similar shapes
broadest below middle - equivalent to lanceolate, ovate, and other similar shapes that are broadest towards the base of the lamina	equally broad throughout much of length - equivalent to oblong, strap-like, and other similar shapes

Leaves (lamina length, in cm)

This feature records the length of the leaf lamina (blade) (in cm) from the base (at point of attachment of the petiole, when petiole attached to base of leaf blade) to the leaf apex, or the longest axis of peltate leaves Leaves (lamina width, in cm) This feature records the width of the leaf lamina (blade) (in cm) at its widest part. This measurement is taken at right angles to the mid-vein or the medial (central) axis of the lamina when the mid-vein is absent or not visible Leaves symmetry at base This feature describes the symmetry of the base of the leaf lamina (blade) on either side of the central vein/axis as being either: very asymmetric symmetric Leaves with margin toothing This feature describes the presence or absence of teeth on the margin of the leaf lamina (blade). The margin is described as: entire - lacking teeth, usually smooth crenate - teeth shallow/small and rounded serrate to dentate (toothed) - more or less strongly/distinctly and sharply toothed Note: this feature should not be confused with whether or not the leaves are dissected or lobed, or whether the leaf margin is undulate Leaves dissected or lobed This feature describes the presence or absence of lobing on the margin of the leaf blade (lamina). The margin is described as: dissected or lobed not dissected or lobed Note: No distinction is made between dissected and lobed leaves. Also, this feature should not be confused with whether the margin of the leaf lamina (blade) is entire or variously toothed, or whether the leaf margin is undulate Leaves dissection type When the leaf blade (lamina) is dissected or lobed, the lobing/dissection is described as either: pinnately lobed palmately lobed Leaves shape of apex The shape of the apex of the leaf lamina (blade) is described as: emarginate or retuse - having notch at the apex or ending in a rounded apex with a rounded sinus (cavity) at the centre rounded - apex rounded like an arc of a circle obtuse - apex gradually ending in a rounded blunt point acute - should be sharp to touch like the point a needle , apex with two almost straight sides mucronate - lamina ending abruptly by a hard short point long-tapering - apex gradually ending in a long reducing point Compound Leaves Leaves when compound, leaf form When the plant has compound leaves, the type of leaves are recorded as: with one leaflet (unifoliate) - a compound leaf reduced to a single leaflet. Compound leaves that consist of a single leaflet are often difficult to distinguish from simple leaves. They are usually recognised by the articulated or jointed ‘petiole’, which is actually a petiole plus a petiolule. with two leaflets (bifoliate) - these compound leaves are referred to as bifoliate with three leaflets (trifoliate) - these compound leaves are referred to as trifoliate pinnate - more than three leaflets and the leaflets are arranged along an unbranched rachis (axis of the leaf) bipinnate - more than three leaflets. This is similar to pinnate, except the rachis is branched once multiply compound - this type of compound leaf has more than two orders of branching before leaflets are formed palmate - this type of compound leaf has more than three leaflets attached at one point to the stalk Petiolule of leaflet, swollen or not The petiolule is the stalk of a leaflet in compound leaves. This feature records the presence or absence of a swelling at either end of the petiolule. The petiolule is recorded as either: not swollen - approximately the same diameter or width throughout length of petiolule swollen at tip, or base, or both Rachis presence The rachis is here used to describe the presence or absence of a stalk-like axis of a compound leaf. It is either: absent, or present Note: the rachis is regarded as absent for compound leaves with only one, two or three leaflets, and for palmate compound leaves that have more than three leaflets attached at one point Rachis wings When the rachis is present, this feature records the presence or absence of a wing along the axis of the rachis. The rachis is either: absent - such that rachis not winged or present - winged Rachis swelling When the rachis is present, this feature records the presence or absence of a swelling at either end of the rachis. The rachis is either: absent - not swollen, more or less the same diameter/width throughout or present - with rachis swollen at either end Leaves when compound, paripinnate or imparipinnate When the tree has pinnate compound leaves, this feature describes the presence or absence of a terminal leaflet. The values for this feature are either: without a terminal leaflet (paripinnate - there is an even number of leaflets and such compound leaves are referred to as paripinnate with a terminal leaflet (imparipinnate) - there is an odd number of leaflets with one leaflet inserted at the apex of the compound leaves. Such compound leaves are referred to as imparipinnate Leaves when compound, leaflet lamina shape type This feature describes the shape of the leaflet blade (lamina) based on the position of its widest part. The values include: broadest above middle - equivalent to oblanceolate, obovate, spathulate, and other similar shapes broadest at or near middle - equivalent to elliptic, oval, and other similar shapes broadest below middle - equivalent to lanceolate, ovate, and other similar shapes equally broad throughout much of length - equivalent to oblong, strap-like, and other similar shapes Leaves when compound, leaflet lamina length (cm) This feature records the length of the leaflet lamina (blade) (in cm) from the base (at point of attachment of the petiolule) to the leaflet apex Leaves when compound, leaflet lamina width (cm) This feature records the width of the leaflet lamina (blade) (in cm) at its widest part. This measurement is taken at right angles to the mid-vein or the medial (central) axis of the lamina when the mid-vein is absent or not visible Leaves when compound, leaflets arrangement This feature describes how the leaflets are inserted on to the rachis. The feature records the arrangement as either: leaflets opposite - leaflets arranged in pairs, opposite one another on the rachis leaflets alternate - leaflets occurring singly along the rachis and alternating from one side of the axis to the other leaflets inserted at one point of the leaf axis - leaflets in palmatifid arrangement or appearing whorl-like Leaves when compound, leaflet symmetry, at base This feature describes the symmetry of the base of the leaflet blade (lamina) on either side of the central vein/axis as being either: asymmetric symmetric Leaves when compound and imparipinnate, terminal leaflet buds When the compound leaves are terminated by a single leaflet (that is, imparipinnate), then the apex of the compound leaf has the following values: terminal developing leaflet buds curled back on itself terminal developing leaflet buds straight terminal developing leaflet buds absent Place mouse over the blue words to view image of example There is a problem with Kingiodendron novoguineense Verdc. This species is paripinnate but it can have only 1-leaflet. Therefore, this species is also recorded as 'terminal developing leaflet buds absent' and 'terminal developing leaflet buds straight' Venation Venation, layout of secondary veins on leaf/leaflet This features describes the arrangement of the secondary veins on the leaves or leaflets (for compound leaves). The values recorded for this feature include: single-veined the leaf or leaflet with only one vein pinnate secondary veins arising from the midrib along its length. The venation of Calophyllum species is scored as pinnate. trinerved three large veins arising from the base palmate more than three large veins arising from the base parallel-veined numerous small veins running in parallel from base, not arising from a midrib. The venation of Araucaria hunsteiniiis scored as parallel-veined. Place mouse over the blue words to view image of example Secondary veins (open or closed) This feature describes the closeness of the secondary veins as either: open spaced far apart to easily see tertiary veins closed spaced so close together that tertiary veins cannot be easily seen between them. For example, the close secondary veins in Calophyllum species Secondary veins prominence This feature describes the distinctiveness/visibility of the secondary veins as: prominent not prominent, but visible not visible Intramarginal veins presence This feature records the presence or absence of an intramarginal vein. The value of this feature is either: present absent Stipules Stipules presence This feature records the presence or absence of stipules at the base of the leaf. Since the stipules may not be persistent, there presence may be indicated by the presence of stipular scars. This feature is recorded as either: absent, or present Stipules freedom When present, the stipules are either: free from one another joined to each other Stipules position The position of the stipules are recorded as either: joined across twigs and so growing between opposite leaves and leaving a scar between them when they fall; hence, interpetiolar laterally placed whether free from each other or joined together Stipules encircling twig When stipules are present, they may be either: encircling the twig (amplexicaul) not encircling the twig Stipules form When stipules are present, several different shapes (form) of stipules may be present. The shapes include: scale-likeoften more or less translucent, usually significantly reduced in size and frequently more or less triangular in shape collar-like stipule is distally truncate such that no clear apex is recognisable, frequently stipules are more or less encircling the twig hair-like stipules are greatly reduced and more or less linear (hence, hair-like) leafy stipules more or less similar in shape to a leaf, usually green spiny stipules reduced to a more or less sharp, linear point (spine) represented by glands stipules modified and glandular Stipules margin The presence of hairs on the margin of the stipules is recorded as either: fringed (fimbriate), hence, hairs present not fringed hence, hairs absent Stipules size The size of the stipules are classified as either: large – easily visible to the eye or small – not easily visible to the eye, often sufficiently small that careful examination is required to view these stipules Stipules persistence The stipules may remain on the twigs and hence are described as persistent or they be non-persistent (caducous). This feature is recorded as either: not persistent, or persistent