Keys Dictionary

Word	Meaning
Nodule	Small swellings on a leaf that contain bacteria, or small knobs on a root that contain nitrogen fixing bacteria.
Nut	A dry, indehiscent fruit with one seed, a protective husk and a hard shell, but no wings. A nut is similar to an achene, but its wall is significantly thickened and hardened.
Oblanceolate	If referring to a leaf, a leaf that is narrowly lance-shaped and widest about two thirds up from the base. Attached to the stem by the pointed end. Compare with lanceolate, which is widest about one third up from the base.
Oblique	Unequal sides at the leaf base.
Obovate	If referring to a leaf, a leaf widest above the middle, toward the apex, and narrowing smoothly toward the base. Similar to an inverted teardrop shape.
Obtuse	If referring to a leaf, a leaf with a rounded or blunt apex.
Ochreous	Ochre-coloured, or a light brownish-yellow.
Operculum	A covering lid over the flower, breaking off to expose the reproductive parts, as in the flowers of Eucalyptus species.
Opposite	In pairs, opposite one another. If referring to leaves, in pairs on a node, on opposite sides of stem.
opposite leaves	Leaves placed opposite one another on the stem.
Orbicular	Flat and approximately circular.
Organelle	A small organ within a cell, such as a chloroplast.
Organic	Organic compounds are produced by or derived from living organisms. Organic compounds contain carbon-hydrogen covalent bonds, which are chemical bonds between carbon atoms and hydrogen atoms, found in living organisms.
Osmosis	Spontaneous diffusion of water or other solvents through a semi-permeable membrane, from a region of higher solute concentration to a region of lower concentration, while blocking unwanted dissolved substances.
Ostiole	A small opening in a fig, or syconium, located at the opposite end to the stalk. The ostiole provides access for pollinating wasps to enter the syconium.
Ovary	The chamber at the base of the style that contains carpels, each of which contains ovules, which become seeds after fertilisation. The style bears the stigma. A superior ovary is located above the petals, and the stamens are attached below its base. An inferior ovary is within the swollen receptacle, below the sepals and petals.
Ovate	If referring to a leaf, being widest in the lower half, toward the petiole, or egg-shaped. See obovate.
Ovoid	If referring to a leaf, being widest in the lower half, toward the petiole, or egg-shaped. See obovate.
Ovule	The minute structure within the ovary that contains an egg cell which, if fertilised, becomes the seed. An ovary may contain one or many ovules.
Pachycaul	A term used for succulent plants that accumulate moisture and nutrients in the root-to-stem section of the plant, creating a thick trunk, disproportionate to the size of the plant.
Palmate	A compound leaf with four or more leaflets, each of which arises from the end of the petiole and radiate outward like the fingers of an open hand. The term digitate is also used. A palmate leaf is not pinnate. The term palmate is also used for 5-lobed simple leaves, shaped like the palm of an open hand with the lobes radiating outward. Lobed simple leaves have deeply indented margins.
Palmately veined	Several primary veins of approximately equal thickness radiating from a single point at the base of the leaf, where the petiole attaches. See Multi-veined.
Panicle	A branched inflorescence in which a central stem develops consecutive side branches, which also branch further, each of which carry two or more flowers. The central stem bears no flowers. A panicle is an inflorescence.
Papillose	Bearing many small and soft nipple-like projections, called Papilla.
Pappus	The tuft of hairs on each seed, which assists in dispersal by wind.
Papyraceous	Usually refers to leaves or other parts of a plant that are papery in texture.
Paripinnate	A pinnately compound leaf with an even number of leaflets. Paripinnate leaves have no terminal leaflet. See imparipinnate.
Pedicel	The stalk of a single flower, at the end of which is the receptacle, on which the floral parts are carried. Refer to peduncle.
Peduncle	The unbranched stalk of a compound inflorescence, ie. a shoot bearing multiple flowers. A fig encloses many flowers, and its stalk is therefore called a peduncle. The term peduncle is also used, in a general sense, for a flower stalk bearing either a solitary flower or an inflorescence. Refer to pedicel.
Pellucid	The term refers to transparent or translucent, allowing light to pass through. Pellucid dots on a leaf are usually secretory cavities that contain citrus oils. The dots appear to transmit light when held up to a light source, such as the sun. In some species, pellucid dots may contain toxins.