Iris(redirected from irides)
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Iris, in Greek mythology
iris, in botany
iris, common name for members of the genus Iris of the Iridaceae, a family of perennial herbs that includes the crocuses, freesias, and gladioli. The family is characterized by thickened stem organs (bulbs, corms, and rhizomes) and by linear or sword-shaped leaves—small and grasslike in the crocuses and blue-eyed grasses. It is widely distributed over the world except in the coldest regions and is most abundant in S Africa and in tropical America. Almost all of the family's 90-odd genera include commercially valuable ornamentals. The iris family is closely related to the lily and amaryllis families, differing from them in having three stamens rather than six. The cultivated irises (genus Iris), freesias (genus Freesia), and gladioli (genus Gladiolus) show a wide variety of colors in their large, usually perfumed blossoms; they are mostly hybrids of Old World species. The many species of wild iris are most common in temperate and subarctic regions of North America, where they are often called flags, or blue flags. The fleur-de-lis is thought to have been derived from the iris, and the flower of the Greek youth Hyacinth may have been an iris. Orrisroot, a violet-scented flavoring used in dentifrices, perfumes, and other products, is prepared from the powdered rhizomes of several European species of iris. The freesias, native to S Africa, characteristically bear their blossoms on a horizontal extension of the stem. The crocuses (genus Crocus), which usually bear a single yellow, purple, or white blossom, are native to the Mediterranean area and to SW Asia. One species, saffron, is cultivated commercially for a yellow dye made from the pollen; the unrelated meadow saffron or autumn crocus and the wild crocus or pasqueflower belong to the lily and buttercup families respectively. Other members of the family found in the United States are the blue-eyed grasses (genus Sisyrinchium) with small clusters of blue, white, or purplish flowers, ranging from Canada to Patagonia, and the celestial lily (genus Nemastylis) with pairs of blue flowers, ranging from the Kansas prairies to Tennessee and Texas. Irises are classified in the division Magnoliophyta, class Liliopsida, order Liliales, family Iridaceae.
(in electron and ion optics), an opening in a conducting plate; used to limit the cross section and vary the expansion (aperture) angle of a charged-particle beam. A round iris under a potential V and placed in an external electrical field is the simplest electrostatic lens. If E1^ and E2 are equal to the field intensity along different sides of the plate at a distance from the aperture, the focal length of such a lens is approximately f = 4ø/ (E1 - E2) where ø is the potential at the center of the iris. Depending on the sign of f, an iris may be a converging or diverging lens. Combinations of irises under different potentials are also electrostatic lenses.
REFERENCEGlaser, V. Osnovy elektronnoi optiki. Moscow, 1957. Sections 77 and 89. (Translated from German.)
a genus of plants of the family Iridaceae. They are perennial rhizomatous herbs with sword-shaped or linear leaves. The flowers are large, with a brightly colored corolliform perianth; the ovary is three-celled and inferior; and the fruit is a trihedral, many-seeded pod.
There are about 200 species, distributed throughout the northern hemisphere; in the USSR there are about 60 species. The iris species that form tubers and bulbs are often subdivided into the genera Junona, Xiphium, Iridodictum, and Gynandriris. Irises are widely used for ornament, especially varieties of the species I. kaempferi, I. hybrida, I. spuria, and I. iberica. They grow best in sunny places with well-drained soil. The orrisroot is obtained from the rootstocks of some irises, and a coarse fiber for making brushes is produced from the leaves of the species I. songarica.
REFERENCESRodionenko, G. I. Rod Iris. Moscow-Leningrad, 1961.
Rodionenko, G. I. Irisy. Moscow, 1961.
G. I. RODIONENKO
a part of the anterior portion of the eye in animals and man that is located between the vitreous and anterior chambers. The iris is a thin and movable diaphragm with a pupillary aperture in the center; light is regulated through the pupil and onto the retina by the contraction and dilation of the aperture.
The iris is composed of both retinal and uveal structures. The retinal, or posterior, surface consists of two pigmented epithelia. The posterior epithelium is covered by an internal restricting membrane and is a continuation of the retina and the ciliated epithelium. The anterior epithelium is a continuation of the pigmented epithelium of the retina and the ciliary body. The neuroepithelial muscles of the iris are the sphincter, which constricts the pupil, and the dilator, which widens the pupil. They are formed from the anterior epithelium. The sphincter is innervated by parasympathetic fibers of the oculomotor nerve and the dilator is innervated by sympathetic nerves.
The uveal, or mesodermal, surface of the iris is also called the anterior surface. It is a continuation of the vascular layer of the ciliary body and the vascular coat and is composed of exterior reticular and deep vascular layers. The uveal surface is covered with endothelium that extends from the cornea. At the level of the restricting membranes of the iris is the barrier that separates blood from the eye. The anterior surface of the iris is divided into a peripheral, or ciliary, zone, which contains both the reticular and vascular layers, and a pupillary zone, which is the lesser circle of the iris and contains the sphincter. The exterior layer of stroma atrophies in the pupillary zone.
The blood vessels of the iris originate in the vascular circulus major located along the margin of the peripheral zone and are positioned radially. In man, they anastamose into the arterial and venous arches of the vascular circulus minor, 1.5 mm from the pupil margin. No independent lymphatic system has been discovered in the iris. The stroma of the iris is composed of thin collagenic and elastic trabeculae. The predominate cells of the stroma are chromatophores, which determine eye color; man has only melanocytes, while birds, reptiles, and amphibians have iridophores and lipophores in addition to melanocytes. There are also fibroblasts and granular plasma cells in the stroma. The color and architectonic of the uveal part of the iris are determined by species and racial characters and change with age.
Inflammation of the iris (iritis) accompanies traumas and various infectious and metabolic diseases; as a rule, there is also inflammation of the ciliary body.
O. G. STROEVA
IRIS(1) See IRIS printer and iris recognition.
(2) The name of Silicon Graphics's first terminals and workstations. The name was later used for SGI's high-availability server software (IRIS FailSafe).
(3) (Infrastructure for Resilient Internet Systems) See DHT.