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Umbelliferae

UMBELLIFERAE, in botany, an order of polypetalous Dicotyledons belonging to the series Umbelliflorae, which includes also the orders Araliaceae (ivy family) and Cornaceae (dogwood family). It contains 180 genera with about 1400 species, occurring 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 Buplcurum, with generally a very characteristic habit, namely stout erect stems with hollow internodes, alternate pinnately compound exstipulate 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 rhizomes such are hogweed ( Heracleum), Angelica, Peucedanum, and others. Some genera have a creeping stem as in Hydrocolyle (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 in "" Britain by sea-holly (E. maritimum), FIG. I. Perfoliate leaf of a j s a large genus of rigid often glaucous species of hare s-ear (Bupleu- herbs with spiny-toothed leaves, rum rotundifohum). 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 palmatejy 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 order.

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 Hydrocolyle. In Eryngium the flowers are crowded into dense heads subtended by a whorl of rigid bracts. A terminal flower is sometimes present as in carrot, where it is distinguished by its form and dark colour. The presence or absence of bracts and their form when present afford useful diagnostic characters. When present at the base of the 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 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 indexed; 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 disk the stylopodium which bears the two styles. Each ovary-cell contains a single pendulous anatropous ovule with a ventral t- p.- f raphe and a single integument. In the HG. 2. Uiagram ,t deve i opment of the flower the stamens flower of Umbelhferae. appear p first> {ollowed by the petals , the 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 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 time. The flowers are generally white, sometimes pink or yellow, very rarely blue; they are generally scented, but the whole plant has an odour 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 acces- sible to quite short-lipped flies. Cross- polliriation is rendered necessary by the flowers being generally markedly proter- androus; 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 or carpophore (fig. 3). The form of the mericarp affords valuable characters for distinguishing genera. On the outer 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 distribution ; they are sometimes thin and Book of Botany, by permission flat as in Heracleum, when they are easily of Swan, Sonnenschein & Co.) carried by the wind, or, as in carrot, pro- p IG , _ ^ pistil- B vided with hooks. The seed contains a small Fruit of the' Caraway embryo embedded in oily endosperm, //-,,. ' which is usually cartilaginous in texture! &S* The order is divided into 9 tribes de- 8 ' pending on the form of the fruit, whether (From Vincs's Student's Tat r n ,,,i\- Carm > ' H n'io-vnniKs Hkk- f ' P stiema ' V s ' , oar . stema compressed, angled, grooved, constricted, di * e ', J n B s th e'two etc. and he r etc., and the presence or absence of vittae. The 35 British genera include representatives of 7 of the tribes. The following may be mentioned: Hydrocotyle (penny- havp = Pna rated to form W P O Seri^ p rt f th Constitutes the nium (Alexanders), Bupleurum (hare's-ear) , Apium (celery, q.v.), Carum (caraway, q.v.), Conopodium or Bunium (earth-nut, q.v.), Myrrhis (Cicely), Chaerophyllum (chervil), Foeniculum (fennel, q.v.), Crithmum (samphire), Oenanthe (water dropwort), Aethusa FIG. 4. Water Dropwort, Oenanthe crocata, with thickened root 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 (hcg's fennel, parsnip, q.v.), Heracleum (hogweed), Daucus (carrot). Petroselinum sativum is common parsley (q.v.).'

Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)

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