ubiquitous (L. ubique: everywhere) adj. Widespread; occurring in a wide variety of habitats.

Ufian See Ufimian.

Ufimian n. 1. The earliest age in the Late Permian epoch, preceded by the Kungurian (Early Permian), followed by the Kazanian, and with a lower boundary dated at 256.1 million years ago. 2. The name of the corresponding eastern European stage, which is roughly contemporaneous with the lower Zechstein (western Europe), lower Guadalupian (N. America), and Basleoan (New Zealand). See also Kazanian.

uliginose See uliginous.

uliginous (L. uliginosus: full of moisture, marshy) adj. Growing in swamps or muddy places. Also uliginose.

ultimate (L. ultimus: farthest) adj. The final section or division of a structure.

Ulva n. A genus of the phylum Oomycota.

umbel (L. umbella: parasol, sunshade) n. A type of racemose inflorescence in which stalked flowers arise from the same point on the flower axis, resembling the spokes of an umbrella. An involucre (cluster) of bracts may occur at the point where the stalks emerge. This arrangement is characteristic of the family Umbelliferae (Apiaceae; e.g. carrot, hogweed, parsley, parsnip), in which the inflorescence is usually a compound umbel.

umbellate (L. umbella: parasol, sunshade) adj. Bearing umbels; consisting of umbels; forming an umbel or umbels.

umbellet (L. umbella: parasol, sunshade) n. An ultimate umbellate cluster of a compound umbel; an umbellule.

umbelliferous (L. umbella: parasol, sunshade; ferre: to carry) adj. Bearing umbels; pertaining or belonging to the Umbelliferae (Apiaceae) family.

umbelliform (L. umbella: parasol, sunshade; forma: shape) adj. An inflorescence with the general appearance, but not necessarily the structure, of a true umbel. The term is often applied to inflorescences which are condensed cymes rather than condensed racemes. Also umbellulate.

umbellulate adj. In the form of or having the appearance of an umbel. Also umbelliform.

umbellule See umbellet.

umbilicate (L. umbilicatus: umbilicate) adj. With a depression in the middle, like a navel.

umbilicus (L. umbilicus: navel) adj. A navel-like structure, as the hilum of a seed.

umbo (L. umbo, umbonis: bump on a shield) n. (pl. umbos or umbones) A rough projection arising from the center of an object, as the thick part of the scale of a pine cone; a rounded knob or protuberance.

umbonate (L. umbo, umbonis: bump on a shield) adj. Possessing an umbo; convex with an abrupt, rounded, central point.

umbonulate (diminutive of L. umbo, umbonis: bump on a shield) adj. With a very small umbo.

umbraculate (L. umbraculum: parasol, sunshade) adj. Umbrella-shaped.

umbraculiferous (L. umbraculum: parasol, sunshade; ferre: to carry) adj. Bearing umbrella-shaped structures.

umbraculiform (L. umbraculum: parasol, sunshade; forma: shape) adj. See umbraculate.

umbraticolous adj. Growing in shady places.

unarmed adj. Lacking spines, prickles, or thorns.

uncate (L. uncatus: curved, hooked) adj. See uncinate.

unciform adj. Hook-shaped.

uncinate (L. uncinus: curved, hooked) adj. Terminating in a hooked point.

unctuous (L. unctus: greasy, oily) adj. Greasy; oily.

undate (L. undatus: wavy) adj. See undulate.

undershrub See subshrub

understory n. An underlying layer of vegetation, especially the plants that grow beneath a forest's canopy.

undulate (L. undulatus: wavy) adj. Wavy, but not so deeply or as pronounced as sinuate. Syn. repand. Cf. sinuate.

undulipodium (L. undulatus: wavy; Gr. pous, podos: foot) n. (pl. undulipodium) A slender flexible outgrowth of a eukaryote cell used for locomotion or propelling fluids over the surface of the cell. The term `undulipodium' is used to designate a eukaryotic `flagellum' or a cilium (which have the same structure), to emphasize the distinction between these structures and the flagellum of a bacterium. Many protoctists and sperm cells swim by means of undulipodia, and various organisms use them to establish feeding currents, or to clear debris from epithelial surfaces. All undulipodia have a shaft, about 0.25 m in diameter, consisting of a longitudinal array of microtubules, the axoneme, which is surrounded by an extension of the cell's plasma membrane. The axoneme has two single microtubules running down the middle surrounded by nine pairs of microtubules. At its base the axoneme connects with a basal body (kinetosome), which organizes assembly of the axoneme microtubules. Cilia are shorter than flagella and move by a whiplike power stroke followed by a recovery stroke in the opposite direction. Flagella generate successive waves that pass from the base to the tip. In both cases, flexing of the shaft is produced by a sliding motion of the microtubule pairs relative to each other. This involves the successive formation and breakage of molecular bridges between adjacent pairs. The bridges are composed of a protein, dynein, and their formation requires energy in the form of ATP.

ungual (L. unguis: nail) adj. Of, pertaining to, or shaped like a nail, or claw. Also ungular.

ungues See unguis.

unguicular (L. unguiculus: nail) See unguiculate.

unguiculate (L. unguiculus: nail) adj. Having clawlike base, as certain petals; ending in a point similar to an animal claw. Also unguicular, unguiculated.

unguiculated See unguiculate.

unguis n. (pl. ungues) The clawlike base of certain petals. Also ungula.

ungula n. (pl. ungulae) Unguis.

ungulae See ungula.

ungular (L. ungula: nail, hoof, claw) adj. Pertaining to or of the nature of an ungula; ungual.

ungulate (L. ungula: nail, hoof, claw) adj. See unguiculate.

uni- prefix. Meaning one.

uniaperturate (L. unus, uni: one; apertura: opening) adj. With a single opening or aperture.

uniaristate (L. unus, uni: one; arista: awn) adj. One-awned.

uniaxial (L. unus, uni: one; axis: axle) adj. With a single unbranched stem terminating in a flower.

unicarpellate See unicarpellous.

unicarpellous (L. unus, uni: one; Gr. karpos: fruit) adj. With a single, free carpel. Also unicarpellate.

unicostate (L. unus, uni: one; costa: rib, side) adj. With a single obvious rib, as in some leaves.

unifacial adj. Said especially of leaves, rounded or terete, i.e. with no adaxial and abaxial surfaces.

uniflorous (L. unus, uni: one; flos, floris: flower) adj. With a single flower

unifoliate (L. unus, uni: one; folia: leaf) adj. Having one leaf.

unifoliolate (L. unus, uni: one; foliolum: small leaf) adj. A leaf theoretically compound, though only expressing a single leaflet and appearing simple, as in Cercis. Syn. one-foliolate.

unijugate (L. unus, uni: one; jugum: yoke) adj. A leaf pinnately compound, but consisting of only two leaflets.

unilacunar adj. Said of nodal anatomy in angiosperms, where one leaf gap is left in the central vascular cylinder when the single leaf trace departs.

unilateral (L. unus, uni: one; lateralis: of the side) adj. One-sided, as in an inflorescence with the flowers all on one side of the axis. Of stamens, with anthers grouped to one side of the style.

unilocular (L. unus, uni: one; loculus: small box) adj. Of an ovary, anther or fruit, having only one internal cavity. Aussi uniloculate.

uniloculate See unilocular.

uniovular adj. monozygotic; derived from a single egg; with a single ovule.

uniovulate (L. unus, uni: one; ovum: egg) adj. With a single ovule. Also uniovular.

uniparous (L. unus, uni: one; parere: to produce. to bear) adj. With only a single axis produced at each branching, as in some cymes.

unipetalous (L. unus, uni: one; Gr. petalon: leaf) adj. With only a single petal.

uniseptate (L. unus, uni: one; septum: fence, partition) adj. With only one septum, as in a silicicle or silique.

uniseriate (L. unus, uni: one; seria: line, sequence) adj. Arranged in a single row or series.

unisexual (L. unus, uni: one; sexus: sex) adj. Bearing only male or only female reproductive organs. Cf. bisexual, perfect.

unistratose adj. One-layered; comprised of a single cell layer as most bryophyte leaves.

united (L. unitas: unity) adj. Fused together.

unitegmic adj. With a single covering over the ovule.

univalent adj. Of a chromosome that is not paired or united with its homologous chromosome during synapsis, bivalents, trivalents, quadrivalents, etc. are associations of 2, 3, 4... homologous chromosomes held together by chiasmata.

unlobed adj. Without lobes.

urceolate (L. urceolus: small jug, small pitcher) adj. Pitcher-like; hollow and contracted near the mouth like a pitcher or urn. The flowers of Vaccinium angustifolium are urceolate.

urceolus (L. urceolus: small jug, small pitcher) n. The perigynium in Carex; any structure resembling a small pitcher.

urceus (L. urceus: jug, pitcher) n. Any structure resembling a pitcher.

urent adj. Stinging.

urn (L. urna: urn, large bow) n. The basal portion of a pyxis; the spore bearing part of the capsule of a moss, between lid and seta. Cf. neck, theca.

urn-shaped See urceolate.

unpollinated See pollinate.

urticoid adj. Said of a leaf tooth in which the medial secondary vein terminates in a non-glandular apex, there are also higher-order convergent lateral veins.

uterotonic adj., n. (Of) a medecine said to have an unspecified positive effect on the uterus.

utricle (L. utriculus: small goatskin) n. An air bladder of aquatic plants; a membranous bladder-like sac enclosing an ovary or fruit; sometimes used for the enlarged cortical cells in Sphagnum and the enlarged water-sac on the first branch leaf of Ceratolejeunea.

utricular (L. utriculus: small goatskin) adj. Of or pertaining to a utricle; bladder-like.

uva n. A grape-like berry formed from a superior ovary.

uvula n. A small, conical, fleshy mass of tissue suspended from the center of the soft palate. soft palate.