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Encyclopedia Britannica - Main :: TUM-VAN |
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UMBELLIFERAE , in botany, an order of polypetalous Di-cotyledons belonging to the series Umbelliflorae, which includes also the orders Araliaceae (ivy family) and Cornaceae (dogwood family). It contains 18o genera with about 1400 species, occur-ring in all parts of the world but chiefly in north temperate regions. It is well represented in the British flora by 35 genera. The plants are annual or perennial herbs, rarely shrubby as sometimes in Bupleurum, with generally a very characteristic habit, namely stout erect stems with hollow internodes, alternate pinnately compound exstipu]ate sheathing leaves and compound umbels of small, generally white, flowers
An example of an annual is the common fool's parsley, Aethusa Cynapium; carrot (Daucus Carota) is a biennial; others are perennial, persisting by means of tubers or rhizomessuch are hogweed (Her- acleum), Angelica, Peucedanum, and others. Some genera have a creeping stem as in Hydrocotyle (pennywort), a small herb with a creeping filiform stem and, in the British species, entire leaves. Bupleurum has simple, entire, often perfoliate leaves (fig. i). Azorella, a large genus in south temperate regions, has a peculiar caespitose habit, forming dense cushions often several feet in diameter and persisting for many years. Eryngium, represented inBritain by sea-holly (E. maritimum), Fin. 1.Perfoliate leaf of a is a large genus of rigid often glaucous species of hares-ear (Bupleu- herbs with spiny-toothed leaves, runt rotundifolium). The two which in some South American lobes at the base of the leaf species with narrow parallel-veined are united, so that the stalk blade and broadly sheathing base appears to come through the recall those of a Monocotyledon such leaf. as Agave or Bromelia. In sanicle (Sanicula), Astrantia and others the leaves are palmately divided; and there is a great variety in the degree of division in the characteristic pinnate leaf, which varies from simply pinnate to a branching of the blade to the fifth or sixth
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 flower as in species of Hydrocotyle. In Eryngium the flowers
The small epigynous flowers are usually hermaphrodite and regular, with parts in fives. The sepals are usually very small, often represented only by 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 long slender filaments bent inwards in the bud but ultimately spreading; the two carpels are in the median plane; the two-celled ovary is surmounted by an epigynous glandular diskthe stylopodiumwhich bears the two styles. Each ovary-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 general presence in the tissues of an ethereal oil or resin. The flower is widely open, the petals and stamens radiating from the central disk (fig. 3, d), on which honey is secreted, and is thus accessible to quite short-lipped flies. Cross-pollination is rendered necessary by the flowers being generally markedly proterandrous; the stamens throughout the umbel have generally shed their pollen before the stigmas have begun to be functional even in the outer flowers. The 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 axis
The fruits are variously adapted for (From vines', Student's Text distribution; they are sometimes thin and Book of Botany, by permission fiat as in Heracleum, when they are easily of Swan, Sonnenschein & Co.) carried by the wind, or, as in carrot, pro- Fro. 3._A, pistil; B, vided with hooks. The seed contains a small Fruit of the 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 (penny- carps (m). Part of of the wort), Eryngium (sea-holly), Sanicula septum constitutes the (sanicle), Conium (hemlock, q.v.), Smyr- carpophore (a). nium (Alexanders), Bupleurum ( hare
fibres, about half nat. size. i, Flower; 2 and 3, Side and front view of fruit; enlarged. (fool's parsley, q.v.), Angelica (q.v.), Peucedanum (hog's fennel, parsnip, q.v.), Heracleum (hogweed), Daucus (carrot). Petroselinum sativum is common parsley (q.v.). sepals and the rudiments of the carpels in succession. The flowers are rendered conspicuous by being massed into more or less dense flat-topped inflorescences. A resemblance to the rayed heads of Compositae
pink
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