Illustrated Glossary of Plant Terminology
This list of terms, which is a subset of the full glossary given within the textbook, is our initial attempt at producing an illustrated glossary. This list deals mainly with floral structures, not vegetative, and does not include example of features found in ferns and gymnosperms. It is our intention to include additional example images in future editions of this CD. Basic terminology of the flowers and fruits are not listed here (such as sepal, petal, stamen, carpel) because they can be seen in hundreds of images. Moreover, the examples chosen to illustrate a particular term are not necessarily the only ones that can be found on the CD for that term. We hope that this list is useful as a learning tool to the student attempting to assimilate the vast vocabulary of plant taxonomy.
Accrescent perianth
Perianth enlarging upon fruit development and maturation. Example 1
Achene
Fairly small, indehiscent, dry fruit with a thin and close-fitting wall surrounding but free from the single seed. Example 1, Example 2, Example 3, Example 4
Acorn
Fruit of the species of Quercus, i.e., a nut associated with a variously scaly cupule. Example 1, Example 2, Example 3, Example 4
Actinomorphic
See Radial symmetry.
Adnate/adnation
Fusion of unlike parts, as stamens with the corolla. Example 1
Aggregate fruit
Fruit that develops from several separate carpels of a single flower. Aggregate of achenes, Example 1; Aggregate of drupes, Example 1, Example 2; Aggregate of follicles, Example 1, Example 2, Example 3
Ament
See Catkin.
Androgynophore
Stalk bearing the androecium (stamens) and gynoecium (carpels), as in some Caryophyllaceae. Example 1
Apetalous
Lacking petals. Example 1, Example 2, Example 3, Example 4, Example 5
Apical placentation
Ovule or ovules attached at the apex of the ovary (Fig. 4.22). Example 1
Apocarpous
Carpels separate. Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, Example 7, Example 8
Apopetalous
Petals separate. Example 1, Example 2 Example 3
Aposepalous
Sepals separate.
Apotepalous
Tepals separate.
Areole
Spiny short-shoot characteristic of the Cactaceae.
Aril
A hard to juicy, often brightly colored outgrowth of the seed; usually developed from the funiculus or the outer integument.
Asymmetrical flower (irregular symmetry)
Flower lacking a plane of symmetry, i.e., neither radial nor bilateral.
Awn
Narrow, bristlelike appendage, often at the tip of a structure such as a fruit or anther. For fruit of Stipa -
Axile placentation
Ovules attached to the central axis of an ovary with two or more locules (Fig. 4.22).
Banner petal
Distinctive adaxial petal, usually the largest, of flowers, especially those of Fabaceae subfam. Faboideae; also called the standard or flag petal.
Basal placentation
Ovule or ovules attached at the base of the ovary (Fig. 4.22).
Basifixed anther
Anther that is attached at its base to the filament.
Bee Pollination (Melittophily)
Beetle Pollination (Cantharophily)
Example 2
Berry
Indehiscent, fleshy fruit with (one or) a few to many seeds; the flesh may be more or less homogeneous, or the outer part of the fruit may be firm, hard, or leathery.
Bilabiate
Two-lipped; typically applied to a calyx or corolla.
Bilateral symmetry
Divisible into equal halves by only one plane of symmetry; also called zygomorphic (Fig. 4.18).
Bird pollination (ornithophily)
Bisexual flower
Flower with both androecium (stamens) and gynoecium (carpels); also called perfect.
Bract
Reduced leaf in the axil of which arises a flower or an inflorescence branch. Involucral around an inflorescence,
Bracteole
Prophyll of a flower, usually very small, borne below the flower on a pedicel; also called a bractlet.
Caducous
Falling off early in development, as in the sepals of some Papaveraceae.
Calyculus
Reduced, rim-like calyx, as in members of Loranthaceae.
Campanulate
Bell or cup-shaped with a broad rim, as in shape of some corollas.
Capitate
Enlarged at the tip, i.e., head-like stigma.
Capitulum
See Head.
Capsule
Dry to rarely fleshy fruit from a two- to many-carpellate gynoecium that opens in various ways to release the seed or seeds.
Carion fly pollination (Sapromyophily)
Carnivorous
Capturing animals and digesting them, as applied to plants. See also insectivorous.
Carpellate flower
Flower with a gynoecium (carpel or carpels) but no functional androecium (stamens).
Caryopsis
Small, indehiscent, dry fruit with a thin wall surrounding and more or less fused to a single seed.
Catkin
Inflorescence consisting of a dense, elongated mass of inconspicuous, usually wind-pollinated flowers; also called an ament. Example 1, Example 2
Cauliflory
Flowers or inflorescences borne on older stems and/or trunks.
Centrifugal development
Developing first at the center and then gradually toward the periphery.
Centripetal development
Developing first at the periphery and then gradually toward the center.
Chasmogamous
Condition of a flower that opens and is usually cross-pollinated; contrast with cleistogamous.
Circumscissile
Structure opening by a line around its circumference, with the top usually coming off as a lid, e.g., a circumscissile capsule.
Clawed
With distinctly narrowed basal portion, as in the clawed petals of Malpighiaceae.
Cleistogamous
Condition of a flower that never opens and is self-pollinated and self-fertilized; contrast with chasmogamous.
Column
Structure formed by the fused style and stigma plus stamens of members of the Orchidaceae.
Complete flower
Flower having a perianth, androecium, and gynoecium.
Compound pistil
A pistil composed of two or more fused (connate) carpels. Example 1.
Compound umbel
Umbel of umbels, i.e., the peduncle of each simple umbel arising from a common point.
Corona
Usually showy outgrowths of the perianth parts, stamens, or receptacle.
Corymb
Raceme with the pedicels of the lowermost flowers elongated, bringing all flowers to more or less the same level, i.e., a flat-topped raceme (Fig. 4.30).
Costapalmate
More or less palmate leaf with an extension of the rachis, forming a midrib (or costa) in the blade, as in the leaves of many palms (Arecaceae).
Cucullate
Hood-shaped, such as the corona on Asclepias.
Cupule
Any cup-shaped structure, such as the scaly to spiny "cup" associated with the nut of members of Fagaceae, or swollen receptacle and perianth parts usually associated with the drupe of members of Lauraceae.
Cyathium
Cuplike cymose inflorescence unit of species of Euphorbia that mimics a single complete flower and consists of one to few nectar glands, several staminate flowers, and a single carpellate flower.
Cyme
Determinate, compound inflorescence composed of repeating units of a pedicel bearing a terminal flower and below it, one or two bracteoles; each bracteole is associated with an axillary flower, and further bracteoles, and so on (Fig. 4.29).
Dehiscent drupe
Fruit with a dry/fibrous to fleshy or leathery outer husk that eventually breaks apart or opens, exposing one or more nutlike pits, as in Carya (Juglandaceae).
Denticidal capsule
Capsule that opens by a series of apical teeth.
Determinate inflorescence
Inflorescence in which the axis is converted into a flower, resulting in the cessation of growth of that axis. See also dichasium.
Diadelphous
Stamens with their filaments fused to form two groups, such as the 9 + 1 condition in some Fabaceae.
Dichasium
A cymose determinate inflorescence composed of three (simple dichasium) or more (compound dichasium) flowers where the terminal units are older than the subtending lateral units.
Didynamous stamens
Four stamens, two long and two short.
Dioecious
With staminate and carpellate flowers borne on separate plants.
Disk flower
Radially symmetrical flower of many members of the Asteraceae.
Distyly
Flowers of different individuals of the same species having two different style lengths, the stamen lengths often varying inversely; an outcrossing mechanism.
Dorsifixed anther
Anther attached dorsally and medially to apex of filament. Example 2.
Drupe
Indehiscent, fleshy fruit in which the outer part is more or less soft (to occasionally leathery or fibrous) and the center contains one or more hard pits or stones consisting of a bony endocarp surrounding a seed or seeds.
Drupelet
Drupe developing from a single carpel and, as traditionally used, one portion of an aggregate fruit, as in Rubus (Rosaceae).
Elaiosome
Hard, oily outgrowth (aril) of a seed that attracts ants.
Epicalyx
A series of bracts that resemble and subtend the calyx, as in some Malvaceae.
Epigynous
With perianth and stamens apparently borne upon the ovary (Fig. 4.21) and the ovary, therefore, inferior.
Epipetalous stamens
Stamens adnate (fused) to the corolla.
Epiphyte
Plant growing upon another plant, which is used as a support.
Equitant leaves
Two-ranked leaves that are flattened in the plane of leaf insertion and with both surfaces morphologically and anatomically identical (i.e., unifacial), as in the leaves of Iris and relatives (Iridaceae).
Exserted floral structures
Sticking out, as in stamens extending beyond the corolla.
Extrafloral nectary
Nectar-producing structure positioned on a non-floral structure, such as a leaf, stipule, stem, bract, or inflorescence axis.
Extrorse anther
Anther that opens outwards, toward the periphery of the flower.
Filament
Stalk of a stamen (Fig. 4.16).
Flag petal
See Banner petal.
Floral cup
See Hypanthium.
Floral tube
See Hypanthium.
Floret
Very small flower, especially those of members of Asteraceae, Cyperaceae, and Poaceae; sometimes applied to the flowers plus associated bract-like structures.
Fly Pollination (myophily)
Pollination by syrphid and bee flies.
Follicle
Dry to rarely fleshy fruit derived from a single carpel that opens along a single (usually adaxial) longitudinal suture.
Free-central placentation
Ovules attached to a freestanding column or central axis in the middle of a unilocular ovary (Fig. 4.22).
Funnel shaped corolla (funnelform)
Same as infundibuliform.
Glandular hair
Hair bearing a knob-like secretory swelling (head) at its apex (Fig. 4.15).
Glumes
Pair of bracts at the base of a grass spikelet.
Grain
See Caryopsis.
Gynobasic style
Style that appears to be inserted at the base of the ovary.
Gynophore
Stalk bearing a gynoecium.
Gynostegium
The floral structure formed by the fusion of the androecium and gynoecium in some members of the pollinial clade of Apocynaceae (e.g. Asclepias).
Half inferior ovary
A floral condition where the floral parts attach midway on the ovary such that it is partly superior and partly inferior.
Haustorium (pl. haustoria)
Specialized root of parasitic plants that penetrates another plant and absorbs water and nutrients.
Hawkmoth pollination (sphingophily)
Head
Compact determinate or indeterminate inflorescence with a very short, often disklike axis and usually sessile flowers (Figs. 4.29, 4.30). Also called a capitulum.
Helicoid cyme
Coiled cyme in which the lateral branches all develop from the same side of the axis (Fig. 4.29).
Hemiparasite
Parasitic plant that is green and able to produce at least some of its own carbohydrates but that has haustorial connections to other plants through which water and nutrients are obtained.
Hesperidium
A berry with a tough exocarp where the fleshy mesocarp is derived from glandular hairs, as in Citrus.
Heterostyly
Flowers in different individuals of the same species having two or three different style lengths, the stamen lengths often varying inversely; an outcrossing mechanism.
Hip
The accessory fruit of Rosa.
Holoparasite
A plant that lacks chlorophyll and obtains from other individuals (hosts) all of its water, nutrients and carbohydrates through haustorial connections.
Hypanthium
Flat, cuplike, or tubular structure on which the sepals, petals, and stamens are borne (Fig. 4.21); usually formed from the fused bases of the perianth parts and stamens or from a modified receptacle; also called a floral cup or floral tube.
Hypogynous
With perianth parts and stamens arising from below the ovary, and the ovary thus superior (Fig. 4.21).
Imperfect flower
Flower lacking either an androecium (stamens) or a gynoecium (carpels); also called a unisexual flower.
Incomplete flower
Flower lacking one or more of the floral parts, i.e., missing either the perianth, androecium, and/or gynoecium.
Inferior ovary
Ovary that is positioned beneath the point of attachment of the other floral parts, which appear, therefore, to arise from its apex (Fig. 4.21).
Insectivory
A nutritional mode evolved in several clades of angiosperms whereby insects and other invertebrates are captured and digested. See also carnivory. Capture mechanisms may involve: Bladders,
Interpetiolar stipules
Stipules positioned at the node between the petiole bases of the opposing leaves, as in Rubiaceae.
Intrastaminal nectar disk
Nectar disk positioned between the androecium (staminal whorl or whorls) and gynoecium.
Introrse anther
Anther that opens inwards, toward the floral axis.
Intruded placenta (pl. placentae)
Placenta that extends into the locule of the ovary (Fig. 4.22).
Involucre
Series of bracts surrounding a flower or inflorescence.
Keel petals
Two abaxial petals of the flowers of Fabaceae subfam. Faboideae; sometimes also used of similar-shaped petals of other families, e.g., Polygalaceae.
Labellum
"Lip" of an orchid perianth; the adaxial member of the inner whorl of perianth parts (but due to rotation of the flower, at anthesis usually placed as the lowermost perianth part), and differentiated from the other perianth parts in size, form, and/or coloration; or two (or four) large, petaloid, and connate staminodes forming a lip-like structure in gingers and relatives.
Laminar stamen
A leaf-like stamen without a distinct anther and filament sometimes with marginal microsporangia.
Legume
Dry, more or less elongated fruit derived from a single carpel that opens, often explosively, along two longitudinal sutures; the most common fruit type of members of Fabaceae.
Liana
Woody climbing plant.
Ligulate flower
Flower with a strap-like, usually five-toothed, corolla limb characteristic of many Asteraceae.
Lobed stigma
A stigma divided into two or more parts.
Locule
Compartment, cavity, or chamber within an ovary or anther.
Loculicidal capsule
Capsule that splits longitudinally between the septa (or placentae, if placentation is parietal) and into the locules (chambers) of the ovary.
Loment
Dry, schizocarpic fruit derived from a single carpel that breaks transversely into one-seeded segments.
Mangrove
Tropical tree that grows in tidally flooded coastal banks or estuaries, showing various adaptations such as salt tolerance or secretion, vivipary, or the development of prop-roots; or the plant community occurring in such regions.
Mistletoe
A branch parasite classified in one of four families of Santalales.
Monadelphous stamens
Stamens fused by their filaments in a single group, usually forming a tube.
Monoecious
Staminate and carpellate flowers separate, but borne on a single plant.
Multiple fruit
Fruit produced by the gynoecia of several closely clustered flowers.
Mycotroph
An association whereby an achlorophyllous plant obtains nutrients via a mycorrhizal fungus attached to a tree root. Occurs in Ericaceae, Gentianaceae, Orchidaceae, etc. Contrast with parasite.
Myrmecophyte
A plant with morphological adaptations to inhabitation by ants, e.g. genera in Rubiaceae.
Nectar disk
Disk-like or ring-like floral nectary.
Nectar spur
Hollow, slender, sac-like projection of a floral part, usually a petal or sepal.
Nectary
Nectar-producing gland, often forming projections, lobes, or disk-like structures.
Nut
Fairly large, indehiscent, dry fruit with a thick bony wall surrounding a single seed.
Nutlet
A small, indehiscent, dry fruit containing a single seed; may in some cases be synonymous with mericarps of a schizocarp.
Ocrea (pl. ocreas, ocreae)
Nodal sheath or tube formed by the stipule(s), e.g., characteristic of most members of Polygonaceae.
Ovule
Structure in seed plants comprised of the female gametophyte, the sporangium, one or two, rarely three, integuments, and a funiculus (stalk); after fertilization, it develops into the seed (Figs. 4.16, 4.17, 4.39).
Panicle
Indeterminate inflorescence with two or more orders of branching, each axis bearing flowers or higher order axes (Fig. 4.30).
Pappus
Highly modified calyx consisting of awns, scales, hairs, or fine bristles, as in members of Asteraceae.
Parasitic plant
A plant that attaches to another by means of a modified root called an haustorium and thereby obtains water and nutrients. Some attach to host branches (stem or aerial parasites) and some to host roots. See also hemiparasite and holoparasite.
Parietal placentation
Ovules attached to the wall of the ovary (Fig. 4.22).
Pedicel
Stalk of a single flower in an inflorescence (Fig. 4.16).
Peduncle
Stalk of a solitary, terminal flower or of an inflorescence (Fig. 4.28).
Pellucid dots
Translucent dots on the surface of a leaf, bract, petal, or other structure usually resulting from cavities or ethereal oil cells in leaf mesophyll or other parenchymatous tissues.
Pepo
Berry-like fruit with a leathery rind found in Cucurbitaceae.
Perfect flower
Flower having both androecium (stamens) and gynoecium (carpels); see bisexual.
Perigynium
Urn-shaped or sac-like prophyll surrounding the carpellate flower of some Cyperaceae, e.g., Carex.
Perigynous
With perianth parts and stamens borne on an hypanthium that surrounds, but is not fused to, the superior ovary (Fig. 4.21).
Phyllaries
Involucral bracts of the heads of members of the Asteraceae.
Pin
Long-styled floral form in a heterostylous species.
Placentation
Arrangement of ovules within the ovary.
Pleurogram
Fine, U-shaped or more or less circular line or groove in the seed coat of some Fabaceae.
Pollinarium
An alternate term used for the pollinium of Orchidaceae.
Pollination syndromes
Floral characteristics associated with pollination by various biotic or abiotic means, e.g., bird-pollination, bee-pollination, wind-pollination, etc.
Pollinium (pl. pollinia)
Mass of pollen grains transported as a unit, as in many Orchidaceae and Apocynaceae.
Polygamous
With both bisexual and unisexual flowers on the same plant. See below for specific examples.
Polygamous, androdioecious
With bisexual and staminate individuals in a population.
Polygamous, andromonoecious
Plants with both bisexual and staminate flowers on the same individual.
Polygamous, gynodioecious
With bisexual and carpellate individuals in a population.
Polygamous, gynomonoecious
Plants with both bisexual and carpellate flowers on the same individual.
Polygamous, polygamodioecious
Within a species or population, some plants with bisexual and staminate flowers, some plants with bisexual and carpellate flowers. Other examples include: Acer rubrum, Actinidia arguta, Gleditsia triacanthos, and Celastrus orbicularis. Example 2
Polygamous, polygamomonoecious (trimonoecism)
Plants with bisexual, staminate, and carpellate flowers on the same individual.
Pome
Indehiscent, fleshy fruit in which the outer part is soft and the center contains papery to cartilaginous structures enclosing the seeds; characteristic fruit of apples, pears, quinces, and most other members of Rosaceae subfam. Maloideae.
Poricidal (or Porose) dehiscence
Opening by means of a pore(s) or flap(s), as in a poricidal capsule.
Protandry
Maturation of anthers, and shedding of pollen before stigmas become receptive (in a bisexual flower or monoecious individual).
Protogyny
Maturation of stigmas before pollen is shed (in a bisexual flower or monoecious individual).
Pseudobulb
Thickened, corm-like internode (or series of internodes) on the stem of many epiphytic orchids (Orchidaceae).
Pulvinus (pl. pulvini)
Swollen portion of the petiole (or petiolule) involved in movement, usually positioned at the petiole base, but sometimes at the apex (Fig. 4.3).
Pyxis
Circumscissile capsule.
Raceme
Simple, indeterminate inflorescence with a single axis bearing pedicellate flowers (Fig. 4.30).
Radial symmetry
Divisible into equal halves by two or more planes of symmetry (Fig. 4.18); also called actinomorphic. Example 1, Example 2
Ray flower
Bilaterally symmetrical, strap-like, apically often three-lobed, carpellate or sterile flower occurring around the periphery of the head of many members of Asteraceae.
Receptacle
Floral axis, which bears the flower parts (Fig. 4.16).
Regular symmetry
See Radial symmetry.
Replum
Persistent, thickened rim (modified placenta) of the fruit that bears the seeds in many Brassicaceae and Papaveraceae.
Resupinate
Twisted 180 degrees; turned up-side down. Compare Encyclia cordilliera (resupinate Example 1).
Rotate corolla
Corolla wheel-shaped, with a short tube and lobes projecting at right angles to the tube.
Ruminate endosperm
Endosperm with regular to irregular ingrowths of the seed coat.
Salverform
Corolla trumpet-shaped, with a thin tube and lobes projecting at right angles to the tube.
Samara
Winged, indehiscent, dry fruit containing a single seed (or rarely two seeds).
Scape
Erect, leafless stem bearing an inflorescence or flower at its apex; usually composed of a single, elongated internode.
Schizocarp
Dry to rarely fleshy fruit breaking into one-seeded (or few-seeded) segments (mericarps).
Scorpioid cyme
Coiled cyme in which the lateral branches (and flowers) develop alternately on opposite sides of the axis (Fig. 4.29).
Seed mimicry
The evolution of similar shapes and colors of seeds in unrelated plant species, such as Abrus and Rhynchosia.
Septicidal capsule
Capsule with longitudinal valves formed by splitting down the middle of the septa (partitions between the locules).
Septum (pl. septa)
Partition or cross-wall, as in an ovary.
Silique
Fruit derived from a two-carpellate gynoecium in which the two halves of the fruit split away from a persistent partition (around the rim of which the seeds are attached); sometimes restricted only to such fruits that are more than twice as long as wide (with shorter fruits then called silicles).
Solitary axillary flower
A single flower formed in the axil of a leaf.
Solitary terminal flower
A single flower formed at the terminus of a vegetative axis.
Spadix
Spike with a thickened, fleshy axis, as characteristic of members of the Araceae.
Spathe
Large bract surrounding or subtending an inflorescence, as the often showy inflorescence bract of members of the Araceae.
Spike
Simple, indeterminate inflorescence with a single axis bearing sessile flowers (Fig. 4.30).
Spikelet
Small spike, as in the basic inflorescence units of members of Poaceae and Cyperaceae.
Spine
Reduced, sharp-pointed leaf or stipule, or sharp-pointed marginal tooth.
Spur
Variously shaped outgrowth of staminal filaments or connectives in Melastomataceae, Ericaceae, and a few other taxa
Staminate flower
Flower with an androecium (stamen or stamens) but not a functional gynoecium (carpel or carpels).
Staminode
Sterile stamen.
Standard petal
See Banner petal.
Stipule
One, usually of a pair of appendages located on either side of (or on) the petiole base; part of the leaf.
Stylopodium (pl. stylopodia)
Enlarged, nectariferous, basal portion of the style of the flowers of Apiaceae.
Succulent
Fleshy and juicy.
Superior ovary
Ovary that arises above the point of insertion of the other flower parts (Fig. 4.21).
Syconium (pl. syconia)
Accessory and multiple fruit characteristic of figs (species of Ficus, Moraceae).
Sympetalous flower
Flower with fused petals.
Synandrous
Having the stamens fused.
Syncarpous
Carpels fused, forming a compound pistil.
Syngenesious stamens
Stamens fused by their anthers.
Syntepalous flower
Flower with fused tepals.
Tactile stamen
A stamen that moves in response to touch, as in Berberis. See also trigger flower. Example 1, Example 2 [ 0608]
Tendril
Elongated and twining structure (modified from an inflorescence, leaf, or stem) assisting in climbing.
Tepal
One of a series of perianth parts that are not differentiated into calyx and corolla.
Tetradynamous stamens
With four long and two short stamens.
Thorn
Reduced, sharp-pointed stem.
Thrum
Short-styled floral form in a heterostylous species.
Trigger flower
Flower with one or more moveable parts that cause the pollen to be forcibly deposited on the pollinator.
Tristyly
Flowers of different individuals of the same species having three different style lengths, the stamen lengths often varying inversely; an outcrossing mechanism.
Tubule
Little tube, as on the anthers of species of Vaccinium (blueberries) and relatives (in the Ericaceae).
Umbel
Determinate or indeterminate inflorescence in which all flowers have pedicels of equal or unequal length that arise from a single region at the apex of the inflorescence axis (Fig. 4.29, 4.30).
Umbraculate stigma
Umbrella-shaped stigma, as found in Sarracenia.
Unifoliolate leaf
Compound leaf that through evolutionary reduction has only a single leaflet; typically distinguished from a simple leaf by the presence of a distinct joint or a pulvinus at the blade-petiole junction, e.g., Citrus, many Berberis.
Unisexual flower
Flower lacking either an androecium (stamens) or a gynoecium (carpels); see Imperfect flower, Staminate flower, Carpellate flower.
Urceolate
Urn-shaped, as in a corolla.
Valvate dehiscence
Opening by valves or flaps, as in anthers in Lauraceae.
Versatile
Structure, such as an anther, that is attached at its midpoint.
Verticel
Whorled, three or more structures at a node, as in flowers in Lamiaceae. Adjectival form verticillate.
Vine
Herbaceous climbing plant.
Viscin
Elastic and/or somewhat sticky material often covering pollen grains or seeds of Viscaceae. Viscin on pollen grains,
Viviparous fruit
Fruit with the seeds germinating while fruit is still attached to the parent plant, as in many mangrove species.
Water pollination (Hydrophyly)
Wind pollination (Anemophily)
Wing
Thin, often-membranous extension or outgrowth of a structure. Also used for the lateral pair of petals in the flowers of Fabaceae subfam. Faboideae, or the lateral petaloid sepals of many Polygalaceae.
Zygomorphic symmetry
See Bilateral symmetry.