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Concept
Celastrales
Résumé
The Celastrales are an order of flowering plants found throughout the tropics and subtropics, with only a few species extending far into the temperate regions. The 1200 to 1350 species are in about 100 genera. All but seven of these genera are in the large family Celastraceae. Until recently, the composition of the order and its division into families varied greatly from one author to another.
The Celastrales are a diverse order that has no conspicuous distinguishing characteristic, so is consequently hard to recognize. The flowers are usually small with a conspicuous nectary disk. The stipules are small or rarely absent. The micropyle has two openings and is therefore called a bistomal micropyle. Flowers with well-developed male and female parts are often functionally unisexual. The seed often has an aril. In bud, the sepals have a quincuncial arrangement. This means that two sepals are inside, two are outside, and the remaining sepal is half inside and half outside.
Perhaps the most conspicuous and unusual trait of the Celastrales is the nectary disk, a feature that it shares with another rosid order, Sapindales. Since the orders are not closely related, the disk must have been an independent development in each of these lines.
The Celastrales are a member of the Celastrales, Oxalidales (including Huaceae), and Malpighiales (COM) clade of Fabidae, with Fabidae being one of the two groups of Eurosids.
The name Celastrales was first used by Thomas Baskerville in 1839. In the time since Baskerville first defined the order, until the 21st century, great differences of opinion occurred about what should be included in the order and in its largest family, the Celastraceae. The family Celastraceae was the only group consistently placed in the order by all authors who accepted it. Because of the ambiguity and complexity of its definition, the Celastraceae became a dumping ground for genera of dubious affinity. Several genera were assigned to this family with considerable doubt about whether they really belonged there.
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