UMBELLIFERAE, in botany, a family of polypetalous di cotyledons belonging to the order Umbelliflorae, which includes also the families Araliaceae (ivy family) and Cornaceae (dogwood family). It contains 200 genera with about 2,700 species, occur ring in all parts of the world but chiefly in north temperate re gions. 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 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 per ennial, persisting by means of tubers or rhizomes—such are hog weed (Heracleum), 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. 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 ; they resemble those of the Australian Raoulia (vegetable sheep). Eryngium, represented in Britain by sea-holly (E. maritimum), is a large genus of rigid often glaucous herbs with spiny-toothed leaves, which in some South American species with narrow parallel veined blade and broadly sheathing base recall those of a mono cotyledon such as Agave or Bromelia. In sanicle (Sanicula), Astrantia and others the leaves are palmately divided.
There is also considerable variety in the development of the umbel, which is usually compound but sometimes simple, as gen erally in Hydrocotyle and Astrantia, rarely reduced to a single 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, distinguished by its form and dark colour, is sometimes present as in carrot (Daucus). The presence or ab sence of bracts and their form when present afford useful di agnostic 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 reg ular, 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 ; the stamens have long slender filaments bent in wards 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, which bears the two styles. Each
ovary-cell contains a single pendulous anatropous ovule with a ventral raphe and a single integument. The flowers are rendered conspicuous by being massed into more or less dense flat-topped inflorescences (umbels). 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 by insects 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, on which honey is secreted, and is thus accessible to short-tongued flies. Cross-pollination is necessary, the flowers being generally pro tandrous.
The fruit is 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. The form of the mericarp affords valuable char acters for distinguishing genera. On the outer surface of each are generally five ridges (primary ridges), between which are sometimes four secondary ridges; oil-cavities, vittae, are often present in the intervening furrows.
The family is classified according to the nature of the flower and fruit. Engler divides the family into three main classes, Hydrocotyloideae, Saniculoideae, Apioideae ; the first two with two subfamilies each, the last with eight. The 35 British genera represent seven of the twelve subfamilies. The following may be mentioned: Hydrocotyle (pennywort), Sanicula (sanicle), Co nium (hemlock, q.v.), Smyrniurn (Alexanders), Apium (celery, q.v.), Carum (caraway, q.v.), Myrrhis (cicely), Foeniculum (fennel, q.v.), Aethusa (fool's parsley, q.v.), Angelica (q.v.), Pas tinaca (parsnip, q.v.), Heracleum (hogweed), Daucus (carrot). It is represented in North America by about 7o genera. The more common ones are Sanicula (black snakeroot), Osmorrhiza (sweet cicely), Cicuta (water hemlock), Siam (water parsnip), Thaspium (meadow parsnip), and Angelica.
For further details see Engler & Prantl, Die Natiirlichen Pflanzen familien (Leipzig, 1887-1908) ; J. C. Willis, Flowering Plants and Ferns (Cambridge, 1925) ; A. B. Rendle, The Classification of Flowering Plants (Cambridge, 1925) .