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Term	Definition
Non-resupinate	Turned 180° in development; e.g., flowers of most orchids in which the lip originates in the uppermost position but twists in such a way that the labellum faces downward at anthesis. Some orchids do not twist, thus the labellum faces up at anthesis.
Nucellus	The tissue that surrounds the megasporophyte or the embryo sac. It is located between the embryo sac and the integument or integuments.
Nuclear endosperm	Endosperm development in which many nuclei develop before cell walls are formed.
Obdiplostemony (obdiplostemonous)	With two series of stamens with twice the number of stamens as petals and those of the outer series inserted opposite the petals and those of the inner series inserted opposite the sepals. Obdiplostemony is sometimes very difficult to determine in flowers at anthesis but become apparent with microtome and SEM studies of bud development (Endress, 2010).
Obturators	In the Styracaceae, outgrowths of the placental wall that partly cover the ovules.
Osmophore	Tissue or a gland, usually associated with flowers, from which aromas emanate.
Ovariodisc	In the Burseraceae, a single, parenchymatous structure representing the ontogenetic fusion of the nectary disc and the pistillode.
Ovary	The part of the gynoecium (=pistil) containing the ovules.
Ovule	The organ that after fertilization becomes the seed. The ovule in angiosperms contains the embryo sac with an egg cell, several other cell types, and is enclosed within the locule of the ovary.
Ovule anatropous	Referring to a curved downward ovule in such a way that the micropyle is close to the funicular attachment.
Ovule campylotropous	Referring to an ovule in which the axis is at an approximately right angle to its stalk (funicle).
Ovule orthotropous	Referring to a straight ovule in which the micropyle is positioned in a straight line and opposite the funicular attachment; referring to a growth habit in which the growing apex is oriented vertically.
Ovules bitegmic	An ovule with two integuments.
Ovules tenuinucellate	The presence of no cells or a single cell layer between the megasporophyte and the epidermal cells in the early development of the megasporophyte.
Palate	In the Lentibulariaceae and Scrophulariaceae, the space at the throat and limb of the corolla used by pollinating insects as a landing platform.
Palea	The upper of the two bracts that enclose the floret in the Poaceae. Compare with lemma.
Papilionaceous corolla	The zygomorphic corolla of most species of papilionoid legumes.
Papilionoid	Referring to flowers similar to those of Fabaceae subfamily Papilionoideae; e.g., those of the Polygalaceae.
Pappus	A modified calyx of hairs, scales, or bristles typical of many Asteraceae.
Parietal placentation	A type of placentation found in compound, unilocular ovaries in which the ovules arise from placentae inserted on the wall of the locule near the sutures.
Pedicel (adj. = pedicellate)	The stalk supporting some flowers.
Perfect flower	Referring to a flower that possesses both male (staminate) and female (pistillate) organs.
Perianth	The collective term for the calyx and the corolla, even when they are not differentiated (i.e., represented by tepals).
Pericarpel	In the Cactaceae, the part of the receptacle fused to the ovary.
Perigon (perigoniate)	A reduced perianth found in the flowers of some species of Araceae, Monimiaceae, and Siparunaceae.
Perigynous ovary	Referring to a flower in which the sepals, petals, and stamens arise from the rim of a cuplike hypanthium surrounding the ovary.
Peripheral filaments	Protein filaments associated with sieve-element plastids.
Personate	Referring to a bilabiate corolla with an expansion on the lower lip that blocks entry into the tube; e.g., in some species of Acanthaceae.
Petal	An outermost segment of the corolla.
Petal lobe	A lobe of the corolla that arises from the corolla tube.
Pistil	The female part of the flower composed of the ovary, style, and stigma.
Pistillate flower	Referring to unisexual flowers with functional gynoecia but without functional stamens (staminodes may be present). Same as female flower.
Pistillode	A rudimentary, sterile gynoecia.
Placenta (plural = placentae)	The structure in the ovary to which the ovules are attached.
Placental obturator	A massive outgrowth of the placenta. In the Styracaceae, the micropyle of each ovule opens upon an obturator; the obturators may or may not be connate.
Placentation	In broadest terms, the arrangement of ovules within the ovary. See axile, basal, free-central, and parietal placentation.
Placentation basal	A type of placentation in which the ovule is attached to the floor of the locule.
Placentation free-central	A type of placentation in which the ovules are borne on a central column arising from the base of a unilocular ovary.
Polar nuclei	Two nuclei that migrate to the center of the embryo sac and fuse with a male nucleus (sperm) to form the primary endosperm nucleus which divides and sometimes forms the endosperm.
Pollen	Male reproductive structures contained within the anther of the stamen and usually released at anthesis. Same as microgametophytes.
Pollinarium (plural = pollinaria)	The pollen-bearing structure of Orchidaceae composed of a viscidium, a stipe, and pollinia.
Pollinium (plural = pollinia)	An aggregate pollen mass characteristic of Orchidaceae and those of Apocynaceae subfamily Asclepiadoideae.
Polyandrous	Referring to an androecium with numerous stamens. Same as polystemonous.
Polypetalous corolla	Having petals free from one another. Same as choripetalous; opposite of sympetalous.
Polystemonous	Having many stamens. Same as polyandrous.
Polysymmetric flower	A flower, capable of being divided, by more than one line passing through the middle of the flower, into two equal parts that are mirror images of one another; e.g., in Gustavia (Lecythidaceae), species of Myrtaceae, and species of Rubiaceae. Same as acinomorphic, radially symmetrical, and regular flowers and opposite of zygomorphic, monosymmetric, bilateral, and irregular flowers. This term can refer to other plant parts as well.
Poricidal anther dehiscence	Referring to anthers that shed their pollen via terminal apertures; e.g., Gustavia spp. (Lecythidaceae) and Solanum spp. (Solanaceae).
Pseudanthium (plural = pseudanthia)	A false flower; e.g., the inflorescence of species of Asteraceae and Dalechampia (Euphorbiaceae).
Pseudodisc	In some Menispermaceae, the button-shaped fleshy whorl of petals.
Pseudostaminodia (singular = pseudostaminodium)	In the Amaranthaceae, referring to sterile, filamentous, entire to fimbriate processes as long as or longer than the stamens and alternating with them.
Pterophyll	Expanded sepal (usually white or green) of some Rubiaceae that usually are expanded fully after anthesis and aid in wind dispersal.
Rachilla	The axis of a spikelet of a Cyperaceae or a Poaceae along which are placed the florets.
Radially symmetrical flower	A flower, capable of being divided, by more than one line passing through the middle of the flower, into two equal parts that are mirror images of one another; e.g., in Gustavia (Lecythidaceae), species of Myrtaceae, and species of Rubiaceae. Same as actinomorphic, polysymmetric, and regular flowers and opposite of zygomorphic, monosymmetric, bilateral, and irregular flowers. This term can refer to other plant parts as well.
Radially symmetrical pollen	In the Malpighiaceae, referring to pollen with pores on the equator and colpi, if present, oriented at right angles to the equator.
Ray flower	A zygomorphic flower with a straplike corolla found in Asteraceae. Compare with disk flower.
Receptacle	The more or less expanded apex of the axis beyond the pedicel upon which the floral parts are borne.
Receptacular throat	In the Cactaceae, the part of the receptacle above the receptacular tube.
Receptacular tube	In the Cactaceae, the broadened part of the receptacle between the summit of the ovary and the point at which the receptacle begins to broaden. Same as epigynous hypanthium.
Recepticle	The thickened part of the pedicel from which the flower organs or the fruits arise. In some accessory fruits, for example the pome and strawberry, the receptacle gives rise to the edible part of the fruit.
Regular flower	A flower, capable of being divided, by more than one line passing through the middle of the flower, into two equal parts that are mirror images of one another; e.g., in Gustavia (Lecythidaceae), species of Myrtaceae, and species of Rubiaceae. Same as actinomorphic, polysymmetric, and radially symmetrical flowers and opposite of zygomorphic, monosymmetric, bilateral, and irregular flowers. This term can refer to other plant parts as well.
Resupinate	Turned 180° in development; e.g., flowers of the Orchidaceae in which the lip originates in the uppermost position but twists 180° so it facing downward at anthesis. Most orchids have resupinate flowers.
Rostellum (plural = rostella)	The portion of the stigma of some Orchidaceae that separates the anther from the fertile part of the stigma and aids in gluing the pollinia to the pollinators; a small beak.
Rotate	Disk-shaped or flat and circular, usually referring to a sympetalous corolla with a short tube and very widely spreading lobes.
Salverform	Referring to the shape of a sympetalous corolla in which the tube is slender and the lobes are abruptly spreading and flat. Same as hypocrateriform and more frequenly used by authors than that term.
Sectile	Referring to the aggregate clumps of soft, granular pollen which distinguishes some species of Orchidaceae. In these species the pollen is easily separated and not aggregated in distinct pollinia.
Sectile pollen	Referring to the aggregate clumps of soft, granular pollen which distinguishes some species of Orchidaceae. In these species the pollen is easily separated and not aggregated in distinct pollinia.
Sepal (sepals)	A segment of the calyx.
Septal nectary	A nectary developing in the septal regions of the ovary.
Septal region	The part or parts of the ovary associated with the septa.
Simple pistil	A gynoecium composed of a single carpel.
Simple style	Referring to a style that is not divided at the apex.
Spathella	Saclike covering of the young flowers of Podostemaceae.
Spur	A tubular, usually nectar-producing outgrowth of a part of a flower; e.g., part of the sepal in some Vochysiaceae.
Stamen	The male part of the flower comprised of the filament and the anther; in the Lecythidaceae stamens are found attached to the staminal tube in those genera that have one (Allantoma, Cariniana, Grias, and Gustavia) and, as far is known, to the staminal ring of species with zygomorphic flowers. Stamens associated with the ligule are hypothesized to be staminodes bearing antherodes and not anthers.
Stamens	The male part of the flower comprised of the filament and the anther.

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