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GENTIANACEAE (the gentian family)
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See also:GENTIANACEAE (the See also:gentian See also:family) , in See also:botany, an See also:order of See also:Dicotyledons belonging to the sub-class Sympetalae or Gamopetalae, and containing about 750 See also:species in 64 genera. It has a See also:world-wide See also:distribution, and representatives adapted to very various conditions, including, for instance, alpine See also:plants, like the true gentians (Gentiana), meadow plants such as the See also:British Chlora perfoliata (yellow-wort) or Erythraea Centaurium(See also:centaury), See also:marsh plants such as Menyanthes trifoliata (See also:bog-See also:bean), floating See also:water plants such as Limnanthemum, or See also:steppe and See also:sea-See also:coast plants such as Cicendia. They are See also:annual or perennial herbs, rarely becoming shrubby, and generally growing erect, with a characteristic forked manner of branching; the See also:Asiatic genus Crawfurdia has a climbing See also:stem; they are often See also:low-growing and See also:caespitose, as in the alpine gentians. The leaves are in decussating pairs (that is, each pair is in a See also:plane at right angles to the previous or succeeding pair), except in Menyanthes and a few allied aquatic or marsh genera, where they are alternate or See also:radical. Several genera, chiefly See also:American, are saprophytes, forming slender low-growing herbs, containing little or no See also:chlorophyll and with leaves reduced to scales; such are Voyria and Leiphaimos, mainly tropical American. The inflorescence is generally cymose, often dichasial, recalling that of See also:Caryophyllaceae, the lateral branches often becoming monochasial; it is sometimes reduced to a few See also:flowers or one only, as in some gentians. The flowers are hermaphrodite, and See also:regular with parts in 4's and 5's, with reduction to 2 in the See also:pistil; in Chlora there are 6 to 8 members in each whorl. The calyx generally forms a See also:tube with See also:teeth or segments which usually overlap in the bud. The corolla shows See also:great variety in See also:form; thus among the British genera it is rotate in Chlora, See also:funnel-shaped in Erythraea, and cylindrical, See also:bell-shaped, funnel-shaped or See also:salver-shaped in Gentiana; the segments are generally See also:twisted to the right in the bud; the See also:throat is often See also:fimbriate or bears scales. The stamens, as many as, and alternating with, the corolla-segments, are inserted at very different heights on the corolla-tube; the filaments are slender, the anthers are usually attached dorsally, are versatile, and dehisce by two See also:longitudinal slits; after See also:escape of the See also:pollen they some-times become spirally twisted as in Erythraza. Dimorphic flowers are frequent, as in the bog-bean (Menyanthes). There is considerable variation in the See also:size, shape and See also:external markings of the pollen grains, and a See also:division of the order into tribes and sub-tribes based primarily on pollen characters has been proposed. The form of the See also:honey-secreting developments of the disk at the See also:base of the ovary also shows considerable variety. The See also:superior ovary is generally one-chambered, with Central figure and See also:figs. 1-4 after See also:Curtis, See also:Flora Londinensis. two variously de- Gentiana Amarella. veloped parietal pla- centas, which occa- I, A small form, natural size. sionally meet, form- 2, Calyx and protruding See also:style. See also:ing two See also:chambers; 3, Corolla, laid open. the ovules are gener- 4, See also:Capsule, bursting into two valves, and ally very numerous showing the seeds attached to their and anatropous or margins. See also:half - anatropous in 5, Floral See also:diagram. form. The style, which varies much in length, is See also:simple, with an undivided or bilobed or See also:bipartite stigma. The See also:fruit is generally a membranous or leathery capsule, splitting septicidally into two valves; the seeds are small and numerous, and contain a small embryo in a copious endosperm. The brilliant See also:colour of the flowers, often occurring in large See also:numbers (as in the alpine gentians), the presence of honey-glands and the frequency of dimorphy and dichogamy, are adaptations for See also:pollination by See also:insect visitors. In the true gentians (Gentiana) the flowers of different species are adapted for widely differing types of insect visitors. Thus Gentiana lutea, with a rotate yellow corolla add freely exposed honey, is adapted to See also:short-tongued insect visitors; G. Pneumonanthe, with a See also:long-tubed, See also:bright See also:blue corolla, is visited by humble bees; and G. verna, with a still longer narrower tube, is visited by See also:Lepidoptera. Gentiana, the largest genus, contains nearly three See also:hundred species, distributed over See also:Europe (including See also:arctic), five being British, the mountains of See also:Asia, See also:south-See also:east See also:Australia and New See also:Zealand, the whole of See also:North See also:America and along the See also:Andes to Cape See also:Horn; it does not occur in See also:Africa. See also:Bitter principles are See also:general in thevegetative parts, especially in the rhizomes and roots, and have given a medicinal value to many species, e.g. Gentiana lutea and others. Additional information and CommentsThere are no comments yet for this article.
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