Glossary - general

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Ubisch body (of pollen grains) – a distinctive, orbicular granule of sporopollenin produced by the tapetum, particularly in plants with secretory tapeta

Ulcerate pollen grain – with ulcus/ulci

Ulcus (pl. ulci; of pollen grains) – pore-like rounded ectoaperture; rounded ectoaperture present at the proximal or distal pole

Umbel – a racemose (indefinite) inflorescence with branches arising from more or less the same point on a common peduncle; simple umbel, where each ray terminates in a flower; compound umbel, where each ray itself bears an umbel, the latter being called a partial umbel

Umbellate – with umbels

Umbelliform – in the shape of an umbel

Umbellule – diminutive of umbel

Umbilicate – navel-like, with a small central hollow or depression

Umbonate – bearing a small boss or elevation in the centre

Umbonulate – with, or ending in, a very small boss or elevation

Unarmed – without spines or prickles

Uncinate hair – hooked

Uncinulate – with minute, strongly hooked hairs

Undulate margin – wavy

Undulate tectum (of pollen grains) – tectum wavy (undulating) in cross-section

Unguiculate sepal or petal – clawed, narrowed into a petiole-like base

Uni- – prefix meaning “with a single”; e.g. unibracteolate, with a single bracteole

Unicellular (of, i.a., hairs) – with a single cell – Opposite: multicellular

Unifacial leaf – oriented edgewise to the stem

Unifoliolate leaf – a compound leaf reduced to a single leaflet, as adduced by the lamina being articulated with the petiole

Uniform – of one shape or form, all more or less similar

Unijugate compound leaf – with a single pair of leaflets

Unilacunar node – with one leaf gap left in the central vascular cylinder when a single leaf trace departs

Unilateral – one-sided; all the organs developed on one side, or all the organs turned to one side

Unilateral paratracheal axial parenchyma – paratracheal parenchyma forming semi-circular hoods or caps only on one side of the vessels and which can extend tangentially or obliquely in an aliform or confluent or banded pattern

Unilocular – with a single locule or cavity

Uniovulate carpel or ovary – with a single ovule

Uniseriate – in a single whorl or series

Uniseriate hair – with a single series (row) of cells

Uniseriate wood ray – one cell wide; may sometimes be converted to a multiseriate ray, when additional ray initials are produced

Unisexual flower – having only male parts, or only female parts

Unitegmic ovule – with a single integument; the sole integument may arise from adnation of two integuments or by suppression of one of the two integuments

Unithecate anther – with a single theca or locule – Opposite: bithecate

Urceolate – urn-shaped, with a short swollen tube contracted near the top and then slighly expanded in a narrow rim

Urticating – with stinging hairs, like an Urtica

Urticoid leaf tooth – with the medial secondary vein terminating in a non-glandular apex, also with higher-order convergent lateral veins

Utricle – (1) (Lentibulariaceae) the traps of Utricularia; (2) (Cyperaceae) a prophyll which has developed into a characteristic bottle-shaped structure and partially to completely surrounds the nutlet in Carex; (3) (Aristolochiaceae) swollen basal part of perianth tube