Celastrales, small order of flowering plants that includes 3 families, some 100 genera, and about 1,350 species. In the Angiosperm Phylogeny Group II (APG II) botanical classification system, Celastrales is placed in the Rosid I clade (see angiosperm).

Celastraceae

Celastraceae, or the bittersweet family, contains about 90 genera with some 1,300 species of trees, lianas, and herbs found throughout temperate and especially tropical regions. Maytenus (including Gymnosporia) contains about 200 species, Salacia about 150 species, and Hippocratea (including Loesneriella) about 120 species; all are pantropical. Euonymus (130 species) is more temperate, while Celastrus (32 species) is intermediate in its preferences.

Fresh leaves of Catha edulis (khat), a plant native in Africa and Arabia, yield a stimulant when chewed. It is especially popular in much of the Middle East. Species of Celastrus and Euonymus in particular are commonly cultivated as ornamental shrubs.

Venus's-flytrap. Venus's-flytrap (Dionaea muscipula) one of the best known of the meat-eating plants. Carnivorous plant, Venus flytrap, Venus fly trap
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Many species in Celastraceae secrete gutta, or latex, and, if a leaf is pulled apart transversely, the two halves often hold together by thin strands of dried latex. The leaves can be spiral or opposite on a single plant, and in some species they are two-ranked. The leaf margins often have teeth, although these may be minute, and there are stipules that are quite often fringed. The flowers are usually small, with three or five stamens facing inward or outward and borne on the outside or inside of the prominent nectary disc. The ovary often has three compartments. The fruits and seeds are variable; the former may be fleshy or dry, and the latter may be winged, with a fleshy appendage or aril, or simply rounded.

Parnassiaceae

Parnassiaceae, with two genera, includes annual to perennial herbs. Parnassia contains 50 species that grow in the north temperate to Arctic region. Lepuropetalon spathulatum, the only species of its genus, occurs in the southeastern United States and Mexico. The leaves in the family have no stipules, and the flowers are single or obviously cymose. There are five stamens and five staminodes, or nonfunctional stamens. The latter are opposite the corolla, and at least sometimes nectar is secreted at their bases. The ovules are borne on the walls of the ovary, and the fruit is a capsule containing many small seeds. L. spathulatum is one of the smallest flowering plants growing on land. It is often less than 2 cm (1 inch) tall, and its flowers lack petals. The staminodes of Parnassia are branched, each branch ending in a shiny yellow knob; these appear to mimic nectaries.

Lepidobotryaceae

Lepidobotryaceae is a small family of two genera and two or three species of trees, Lepidobotrys staudtii being known from East Africa and Ruptiliocarpon caracolito growing in Central and South America. They have simple two-ranked leaves that are jointed at the base of the blade and have small paired leafy structures, or stipels, as well as ordinary stipules where the leaf joins the stem. The inflorescence seems to arise opposite the leaves. The flowers are small, male and female flowers being borne on different plants. The sepals and petals are free, and the 10 stamens are joined at their bases. The fruit wall has a layer with distinctive radial fibres that separate from a horny inner layer.

Paul E. Berry
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What are angiosperms?

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angiosperm, any of about 352,000 species of flowering plants, the largest and most diverse group within the kingdom Plantae. Angiosperms represent approximately 80 percent of all the known green plants now living. The angiosperms are vascular seed plants in which the ovule (egg) is fertilized and develops into a seed in an enclosed hollow ovary. The ovary itself is usually enclosed in a flower, that part of the angiospermous plant that contains the male or female reproductive organs or both. Fruits are derived from the maturing floral organs of the angiospermous plant and are therefore characteristic of angiosperms. By contrast, in gymnosperms (e.g., conifers and cycads), the other large group of vascular seed plants, the seeds do not develop enclosed within an ovary but are usually borne exposed on the surfaces of reproductive structures, such as cones.

Unlike such nonvascular plants as the bryophytes, in which all cells in the plant body participate in every function necessary to support, nourish, and extend the plant body (e.g., nutrition, photosynthesis, and cell division), angiosperms have evolved specialized cells and tissues that carry out these functions and have further evolved specialized vascular tissues (xylem and phloem) that translocate the water and nutrients to all areas of the plant body. The specialization of the plant body, which has evolved as an adaptation to a principally terrestrial habitat, includes extensive root systems that anchor the plant and absorb water and minerals from the soil; a stem that supports the growing plant body; and leaves, which are the principal sites of photosynthesis for most angiospermous plants. Another significant evolutionary advancement over the nonvascular and the more primitive vascular plants is the presence of localized regions for plant growth, called meristems and cambia, which extend the length and width of the plant body, respectively. Except under certain conditions, these regions are the only areas in which mitotic cell division takes place in the plant body, although cell differentiation continues to occur over the life of the plant.

The angiosperms dominate Earth’s surface and vegetation in more environments, particularly terrestrial habitats, than any other group of plants. As a result, angiosperms are the most important ultimate source of food for birds and mammals, including humans. In addition, the flowering plants are the most economically important group of green plants, serving as a source of pharmaceuticals, fiber products, timber, ornamentals, and other commercial products.

Although the taxonomy of the angiosperms is still incompletely known, the latest classification system incorporates a large body of comparative data derived from studies of DNA sequences. It is known as the Angiosperm Phylogeny Group IV (APG IV) botanical classification system. The angiosperms came to be considered a group at the division level (comparable to the phylum level in animal classification systems) called Anthophyta, though the APG system recognizes only informal groups above the level of order.

Throughout this article the orders or families are given, usually parenthetically, following the vernacular or scientific name of a plant. Following taxonomic conventions, genera and species are italicized. The higher taxa are readily identified by their suffixes: families end in -aceae and orders in -ales.

trees deciduous and coniferous. trees grow on a bank of a forest in springtime in Alberta, British Columbia, Canada. logging, forestry, wood, lumber, wilderness
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For a comparison of angiosperms with the other major groups of plants, see plant, bryophyte, fern, lower vascular plant, and gymnosperm.