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Term Definition
Actinomorphic 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 (Lecythidaceae), species of Myrtaceae, and species of Rubiaceae. Same as polysymmetric, radially symmetrical, and regular flowers and opposite of zygomorphic, monosymmetric, bilateral, and irregular flowers. This term can refer to other plant parts as well. Flower of Gustavia brachycarpa. Photo by R. Aguilar.
Aestivation The arrangement of the parts of the perianth in the floral bud. Corolla aestivation. Photo by S. A. Mori.
Amphitropous Referring to an ovule with a curved embryo sac in which the stalk (funicle) is curved such that the tip of the ovule and the base of the stalk are near one another. Compare with anatropous. Corolla aestivation. Photo by S. A. Mori.
Androecial hood In the Lecythidaceae, the distal part of the ligule that has become modified either structurally by coiling inward or by the production of staminodes, vestigial stamens, or nectar-producing vestigial stamens. Androecial hoods are usuallly separated from the staminal ring by an appendage-free part of the ligule (the only known exception is Couroupita nicaraguarensis and perhaps a species of the Lecythis sec. Pisonis group not yet identified. Androecial hoods of Lecythidaceae vary according to their degree of structural complexity and the type of androecial appendages they possess. Principal parts of the androecium of a zygomorphic-flowered Lecythidaceae. Drawing by B. Angell
Androecium (plural = androecia) The collective term for the staminate structures (i.e., the stamens and staminodes) of a flower; the stamens as a unit. Floral parts of a papilionoid legume. Photo by S. A. Mori.
Androgynophore A stalk that is elevated above the point of perianth attachment and supports the androecium and gynoecium; e.g., species of Passifloraceae. Medial section of a flower of Passiflora. Drawing by B. Angell.
Androphore A stalk elevated above the point of perianth attachment and supporting the stamens; e.g., the united filaments of species of Menispermaceae and Myristicaceae. Flowers of two species of Myristicaceae. Photos by C. A. Gracie.
Andropodium In the Podostemaceae, a stalk formed as the result of fusion of the filaments. Flowers of two species of Myristicaceae. Photos by C. A. Gracie.
Antepetalous Referring to structures, usually stamens, inserted opposite or facing the petals. Corollas from the ground of a species of Sapotaceae. Photo by S. A. Mori.
Antesepalous Referring to structures, usually stamens, inserted opposite or facing the sepals. A flower with reflexed stamens. Drawing by B. Angell.
Anther The pollen-bearing part of the stamen. Complete flower. Drawing by B. Angell.
Anther dehiscence lateral Referring to the anthers of many flowering plants that open along the side. Lateral and poricidal anther dehiscence. Drawing by B. Angell.
Anther sac See theca. Lateral and poricidal anther dehiscence. Drawing by B. Angell.
Anther versatile A stamen in which the filament is attached to the anther above the base of the anther. Versatile and basifixed anthers. Drawing by B. Angell.
Antheriferous Bearing anthers. Versatile and basifixed anthers. Drawing by B. Angell.
Antherode The anther of a staminode; an anther that bears pollen that does not germinate; in the Lecythidaceae, antherodes are found in the androecial hood and in the innermost row of anthers on the ligular side of the staminal ring of some species, in the Lecythidaceae antherodes are often different in color, usually yellow, than the anthers of the stamens which are usually white. Comparison of fodder pollen position between two species of Corythophora
Anthers basifixed Referring to an anther attached to the filament at its base. Medeola virginiana. Photos by S. A. Mori.
Anthesis The expanding and opening of a flower. Anthesis. Photos by S. A. Mori.
Antipodals Three cells located at the end of the matural megagametophyte opposite the micropyle. These cell apparently have no function and desintegrate after fertilization. A mature megagametophyte of an angiosperm. Drawing by M. Sashital.
Apetalous flower Without petals. Unisexual flowers of Pistacia lentiscus. Photo by S. A. Mori.
Apical placentation A type of placentation in which the ovules are attached at the apex of the locule. See placentation. Placentation of Grias neuberthii. Photo by X. Cornejo.
Apotropous Referring to an ovule with a ventral raphe. Placentation of Grias neuberthii. Photo by X. Cornejo.
Ascending-cochleate Referring to a type of corolla aestivation in the Acanthaceae in which one petal, being larger than the others covers the other petals in bud. Placentation of Grias neuberthii. Photo by X. Cornejo.
Asymmetric flower Same as zygomorphic flower. Placentation of Grias neuberthii. Photo by X. Cornejo.
Aureole See eyespot. Placentation of Grias neuberthii. Photo by X. Cornejo.
Axile placentation A type of ovule arrangement in which the ovules arise from placental tissue derived from the apices of the septa of a locule. In this type of placentation the apices of the septa are fused or in very close proximity to one another. Axile placentation. Photo by S. A. Mori.
Banner The upper, broad petal of Fabaceae. Same as standard, banner, and vexillum with standard the preferred term. Floral parts of a papilionoid legume. Photo by S. A. Mori.
Basal placentation A type of placentation in which the ovules arise from the base of the locule. Axile, parietal, free-central, and basal placentation. Drawing by B. Angell.
Bilabiate Two-lipped, usually referring to zygomorphic calyces and corollas such as those found in the Lamiaceae. Axile, parietal, free-central, and basal placentation. Drawing by B. Angell.
Bilaterally symmetrical flower A flower capable of being divided into only two equal parts (mirror images) by a line passing through the middle of a flower, i.e., other lines passing the middle of the flower will not give mirror images of one another; same as zygomorphic, monosymmetric, and irregular flowers and opposite of actinomorphic, monosymmetric, radially symmetrical, and regular flowers. This term can refer to other plant parts as well. Zygomorphic flower of a legume. Photo by S. A. Mori.
Bilocular Having two locules. 2-locular ovary of Eschweilera tenuifolia. Photo by C. Potascheff.
Binucleate pollen Referring to pollen grains that have two nuclei when shed from the anthers. Compare with trinucleate pollen. 2-locular ovary of Eschweilera tenuifolia. Photo by C. Potascheff.
Biseriate perianth Referring to a perianth with two whorls or rows; i. e. with both calyx and corolla. Compare with uniseriate. Parts of the perianth. Drawing by B. Angell
Bisexual flower Referring to a flower with a functional androecium and a functional gynoecium. Same as perfect. Complete flower. Drawing by B. Angell.
Bracteole A small bract usually inserted on the pedicel. Bract and bracteoles of Couroupita guianensis. Photo by S. A. Mori.
Bracteoles above articulation Bracteoles inserted above the articulation in the pedicel/hypanthium continuum of Lecythidaceae. Position of bracteoles as seen in Gustavia hexapetala. Drawing by B. Angell.
Bracteoles below articulation Bracteoles inserted below the articulation in the pedicel/hypanthium continuum of Lecythidaceae. Bract and bracteoles of Couroupita guianensis. Photo by S. A. Mori.
Callus A thickened part of an organ; e.g., in some Orchidaceae, the fleshy outgrowth of the labellum, or in the Poaceae, the hardened base of the spikelet or floret just above the point of disarticulation. Lips of two species of Orchidaceae. Drawing  by B. Angell.
Calycine Belonging to the calyx; e.g., in species of Lecythidaceae, the calycine rim, or line of scars left by the calyx. Lips of two species of Orchidaceae. Drawing  by B. Angell.
Calyx (plural = calyces) The outer circle or first whorl of floral parts; a collective term for the sepals. Parts of the perianth. Drawing by B. Angell