umbel (4 images): a racemose inflorescence with a very short axis and more elongate pedicels that seem to arise from a common point.

umbellate: in umbels.

umbellet: one of the ultimate umbellate clusters of a compound umbel.

umbelliform: with the form but not the structure of an umbel.

umbo (1 image): a blunt or rounded elevation or protuberance on the end or side of a solid organ, as on the scales of many pine cones.

umbonate: provided with an umbo.

uncinate (5 images): hooked at the tip.

undulate: wavy.

uniseriate: in one series or row (e.g., bracts of an involucre).

unisexual flower: one with an androecium or a gynoecium, but not both.

urceolate (5 images): urn-shaped or pitcherlike, contracted at or just below the mouth.

utricle: a small, thin-walled, 1-seeded, more or less inflated fruit.