RANUNCULACEAE, in botany, a family of Dicotyledons belonging to the series Ranales, and containing 4o genera with about 700 species, which are distributed through temperate and cold regions but occur more especially in the northern hemi sphere. It is generally regarded as a genetic family which gave rise to the higher Dicotyledons, as well as the Monocotyledons. It contains many well known forms, such as buttercup, larkspur, anemone, columbine, clematis, marsh marigold, peony, etc. It is well represented in Britain, where 12 genera are native. In North America there are about 25 genera. The plants are mostly herbs, rarely shrubby, as in Clematis, which climbs by means of the leaf stalks, with alternate leaves, opposite in Clematis, generally with out stipules. The flowers, which show considerable variation in the number and development of parts, are characterized by free hypogynous sepals and petals, numerous free stamens, usually many free one-celled carpels and small seeds containing a minute straight embryo embedded in a copious endosperm. The parts of the flower are generally arranged spirally on a convex receptacle. The fruit is one-seeded, an achene or a many-seeded follicle, rarely, as in Actaea, a berry.
The family falls into several well-defined tribes which are dis tinguished by characters of the flower and fruit all are repre sented among British native or commonly grown garden plants.
Tribe I. Paeonieae, peony group, are mostly herbs with deeply cut leaves and large solitary showy flowers in which the parts are spirally arranged, the sepals, generally five in number, passing gradually into the large coloured petals. There are 2-5 free carpels which bear a double row of ovules along the ventral suture. There are no honey-leaves (nectaries) but honey is secreted by a ring like swelling round the base of the carpels, which become fleshy in the fruit and dehisce along the ventral suture. There are only three genera, the largest of which, Paeonia, occurs in Europe, tern perate Asia and western North America. P. officinalis is the com mon peony.
Tribe II. Helleboreae are almost exclusively north temperate or subarctic. The plants are herbs, either annual, e.g., Nigella (love in-a-mist), or perennial by means of a rhizome, as in Aconitum or Eranthis (winter aconite). The leaves are simple, as in Caltha, but
more often palmately divided as in hellebore, aconite and larkspur. The flowers are solitary (Eranthis) or in cymes or racemes, and are generally regular as in Caltha (king-cup, marsh marigold), Trollius (globe-flower), Helleborus (hellebore), Aquilegia (col umbine) ; sometimes markedly irregular as in Aconitum (aconite) and Delphinium (larkspur). The carpels, generally three to five in number, form in the fruit a many-seeded follicle, except in Actaea (baneberry), where the single carpel develops to form a many-seeded berry, and in Nigella, where the five carpels unite to form a five-chambered ovary. There is considerable variety in the form of the floral envelopes and the arrangement of the parts. The outer series, or sepals, generally five in number, is generally white or bright-coloured. Thus in Caltha and Trollius the sepals form a brilliant golden-yellow cup or globe, and in Eranthis a pale yellow star which contrasts with the green involucre of bracts immediately below it ; in Nigella they are blue or yellow, and also coloured in Aquilegia. In Helleborus the greenish sepals persist • • till the fruit is ripe. Aconitum and Delphinium differ in the irreg ular development of the sepals, the posterior sepal being dis tinguished from the remaining four by its helmet-shape (Aconi tum) or spur-shape (Delphin ium). In Caltha there are no petals, but in the other genera there are honey-secreting and storing structures varying in num ber and in form in the different genera. In Trollius they are long and narrow with a honey-secreting pit at the base, in Nigella and Helleborus they form short stalked pitchers, in Aquilegia, they are large and coloured with a showy petal-like upper portion and a long basal spur in the tip of which is the nectary. In Delphin ium they are also spurred, and in Aconitum form a spur-like sac on a long stalk. The parts of the flower are generally arranged in a spiral (acyclic), but are sometimes hemicyclic, the perianth form ing a whorl as in winter aconite; rarely is the flower cyclic, as in Aquilegia, in which case the parts throughout are arranged in alternating whorls. In Caltha, where there are no petals, honey is secreted by two shallow depressions situated on the side of each carpel.