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UMBELLIFERAE
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UMBELLIFERAE , in See also:botany, an See also:order of polypetalous Di-cotyledons belonging to the See also:series Umbelliflorae, which includes also the orders Araliaceae (See also:ivy See also:family) and Cornaceae (See also:dogwood family). It contains 18o genera with about 1400 See also:species, occur-See also:ring in all parts of the See also:world but chiefly in See also:north temperate regions. It is well represented in the See also:British See also:flora by 35 genera. The See also:plants are See also:annual or perennial herbs, rarely shrubby as sometimes in Bupleurum, with generally a very characteristic See also:habit, namely stout erect stems with hollow internodes, alternate pinnately See also:compound exstipu]See also:ate sheathing leaves and compound umbels of small, generally See also: There is also considerable variety in the development of the umbel, which is usually compound but sometimes simple, as generally in Hydrocotyle and Astrantia, rarely reduced to a single See also:flower as in species of Hydrocotyle. In Eryngium the flowers are crowded into dense heads subtended by a whorl of rigid bracts. A terminal flower is sometimes See also:present as in carrot, where it is distinguished by its See also:form and dark See also:colour. The presence or See also:absence of bracts and their form when present afford useful diagnostic characters. When present at the base of the See also:primary rays of the umbel they form the involucre, and the involucel when at the base of a partial umbel. In Astrantia the simple umbel is enveloped by a large, often coloured, involucre. The small epigynous flowers are usually hermaphrodite and See also:regular, with parts in See also:fives. The sepals are usually very small, often represented only by See also:teeth on the upper edge of the ovary; the petals are usually obovate or obcordate in shape, often with the tip inflexed; .,, y the stamens have See also:long slender filaments See also:bent inwards in the bud but ultimately spreading; the two carpels are in the median See also:plane; the two-celled ovary is surmounted by an epigynous glandular disk—the stylopodium—which bears the two styles. Each ovary-See also:cell contains a single pendulous anatropous ovule with a ventral raphe and a single integument. In the development of the flower the stamens appear first, followed by the petals, theodour from the See also:general presence in the tissues of an ethereal oil or See also:resin. The flower is widely open, the petals and stamens radiating from the central disk (fig. 3, d), on which See also:honey is secreted, and is thus accessible to quite See also:short-lipped flies. See also:Cross-See also:pollination is rendered necessary by the flowers being generally markedly proterandrous; the stamens throughout the umbel have generally See also:shed their See also:pollen before the stigmas have begun to be functional even in the See also:outer flowers. The See also:fruit is again very characteristic; a schizocarp which splits down the septum to form two dry one-seeded mericarps which are at first attached to, or pendulous from, an entire or split central See also:axis or carpophore (fig. 3). The form of the mericarp affords valuable characters for distinguishing genera. On the outer See also:surface of each are generally 5 ridges (primary ridges), between which are sometimes 4 secondary ridges; oil-cavities, vittae, are often present in the intervening furrows. The fruits are variously adapted for (From vines', Student's See also:Text See also:distribution; they are sometimes thin and See also:Book of Botany, by permission fiat as in Heracleum, when they are easily of See also:Swan, Sonnenschein & Co.) carried by the See also:wind, or, as in carrot, See also:pro- Fro. 3._A, See also:pistil; B, vided with hooks. The See also:seed contains a small Fruit of the See also:Caraway embryo embedded in oily endosperm, (Carum Carui) ; en-which is usually cartilaginous in texture. larged. The order is divided into 9 tribes de- d, epigynous disk; f, pending on the form of the fruit, whether compressed, angled, grooved, constricted, ovary; n stigma; two &c., and the presence or absence of vittae. carpell. I n B the two The 3r, British genera include represen- carpels have separated tatives of 7 of the tribes. The following cap as i- to form two te may be mentioned : Hydrocotyle (See also:penny- carps (m). See also:Part of of the wort), Eryngium (sea-holly), Sanicula septum constitutes the (sanicle), Conium (See also:hemlock, q.v.), Smyr- carpophore (a). nium (See also:Alexanders), Bupleurum (See also:hare's-ear), Apium (See also:celery, q.v.), Carum (caraway, q.v.), Conopodium or Bunium (See also:earth-See also:nut, q.v.), Myrrhis (See also:Cicely), Chaerophyllum (chervil), Foeniculum (See also:fennel, q.v.), Crithmum (samphire), Oenanthe (See also:water See also:dropwort), Aethusa See also:fibres, about See also:half nat. See also:size. i, Flower; 2 and 3, See also:Side and front view of fruit; enlarged. (fool's parsley, q.v.), Angelica (q.v.), Peucedanum (hog's fennel, See also:parsnip, q.v.), Heracleum (hogweed), Daucus (carrot). Petroselinum sativum is common parsley (q.v.). sepals and the rudiments of the carpels in See also:succession. The flowers are rendered conspicuous by being massed into more or less dense See also:flat-topped inflorescences. A resemblance to the rayed heads of See also:Compositae is suggested in the frequently larger size of the flowers on the circumference of the umbel which are often sterile and zygomorphic from the larger size of the outer petals. This arrangement allows a large number of flowers to be visited in a short See also:time. Additional information and CommentsThere are no comments yet for this article.
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