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Umbel
An inflorescence where all the flower stalks arise from the same point, usually the tip, and are of a similar length, eg, cow parsley.
Understorey
A layer of vegetation, comprising shrubs and small trees, which grows beneath larger trees. Ground cover in a forest or wood.
Undulate
To be wavy. The term can be used to describe leaves or petals that have undulating surfaces or margins.
Unisexual
Being of one sex. Each flower is either male or female, however, plants may bear flowers of different sexes. See Monoecious.
