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[citation needed] Leaves may be simple, with a single leaf blade, or compound, with several leaflets. Compound leaves may be pinnate with pinnae (leaflets) on both sides of a rachis (axis), or may be palmate with multiple leaflets arising from a single point. [1] Leaf structure is described by several terms that include:
The two main classes of compound leaf morphology are palmate and pinnate. For example, a hemp plant has palmate compound leaves, whereas some species of Acacia have pinnate leaves. The ultimate free division (or leaflet) of a compound leaf, or a pinnate subdivision of a multipinnate leaf is called a pinnule or pinnula.
The middle vein of a compound leaf or a frond, when it is present, is called a rachis. Palmately compound The leaflets all have a common point of attachment at the end of the petiole, radiating like fingers of a hand; for example, Cannabis (hemp) and Aesculus (buckeyes). Pinnately compound Leaflets are arranged either side of the main axis, or ...
Some fronds are not pinnately compound (or simple), but may be palmate, costapalmate, or bifurcate. There is a spectrum from costapalmate to palmate. Costapalmate fronds are shaped like the palm of a hand and have a short midrib or costa. Palmate fronds are also shaped like the palm of the hand, but all ribs or leaflets arise from a central area.
Palms have large, evergreen leaves that are either palmately ('fan-leaved') or pinnately ('feather-leaved') compound and spirally arranged at the top of the stem. The leaves have a tubular sheath at the base that usually splits open on one side at maturity. [9]
paripinnate: pinnately compound leaves in which leaflets are borne in pairs along the rachis without a single terminal leaflet; also called "even-pinnate". imparipinnate: pinnately compound leaves in which there is a lone terminal leaflet rather than a terminal pair of leaflets; also called "odd-pinnate".
Vein – the externally visible vascular bundles found on leaves, petals, and other parts. Veinlet – a small vein. Leaf Arrangement or Phyllotaxy: Whorl – three or more leaves or branches or pedicels arising from the same node. Leaf Type: Abruptly pinnate – a compound leaf without a terminal leaflet. Leaf Blade Shape:
Having a definite costa (midrib), unlike the typical palmate or fan leaf, but with the leaflet s arranged radially as in a palmate leaf. cotyledon The primary leaf or leaves of a plant embryo which upon germination develops into the seed-leaf or the first set of leaves. craspedodromous Pinnate venation in which the secondary veins terminate at ...