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Encyclopedia Britannica - Main :: PYR-RAY |
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RANUNCULACEAE , in botany, a natural order of Dicotyledons belonging to the subclass Polypetalae, and containing 27 genera with about Soo species, which are distributed through temperate and cold regions but occur more especially beyond the tropics in the northern hemisphere. It is well represented in Britain, where 11 genera are native. 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 without stipules, and flowers
a convex receptacle. The fruit is one-seeded, an achene (fig. 3), or a many-seeded follicle (fig. 4), rarely, as in Actaea, a berry. From Vines's Students' Text Book of Botany, by permission of Swan, Sonnenschein & Co.. From Strasburger's Lehr-Mich der Botanik, by per-mission of Gustav Fischer. represented 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
bear a double row of ovules along the ventral suture. Honey is secreted by a ring-like swelling round the base of the carpels, which become fleshy or leathery in the fruit and dehisce along the ventral suture. There are only three genera, the largest of which, Paeonia, occurs in Europe, temperate Asia and western North America. P. officinalis is the common peony.Tribe II. Helleboreae are almost exclusively north temperate or subarctic; there are 15 genera, several of which are represented in the British flora. 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). They leaves are simple, as in Caltha, but 'more often palmately divided as in hellebore
cymes or racemes, and are generally regular as in Caltha (king-cup, marsh marigold
baneberry
series , or sepals, generally five in number, is generally white or bright -coloured, serving as an attraction for insects, especially bees, as well as a protection for the rest of the flower. 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 Hellebore
the posterior sepal being distinguished from the remaining four by its helmet-shape (Aconitum) or spur (Delphinium). In Caltha there are no petals, but in the other genera there are honey-secreting and storing structures varying in number 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 (fig. 7) they form short- 2, nectary, side and front view (nat. size). 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 Delphinium they are also spurred, and in Aconitum form a spur-like sac on a long stalk (fig. 8). The parts of the flower are gene- rally arranged in a spiral (acyclic), but are sometimes hemicyclic, the perianth forming a whorl as in winter aconite; rarely is the flower cyclic, as in Aquilegia (fig. 9) where the parts throughout are arranged in alternating whorls. In Caltha, where there are no petals, honey is secreted by two shallow depressions on the side of each carpel. Tribe III. Anemoneae, with 8 genera, are chiefly north temperate, arctic and alpine plants, but also pass beyond the tropics to the southern hemisphere. They differ from the two preceding tribes in the numerous carpels, each with only one ovule, forming a fruit of numerous achenes. They are annual or perennial herbs, erect as in Anemone, Thalictrum (meadow-rue) and many buttercups, orcreeping as in Ranunculus repens; the section Batrachium of the genus Ranunculus (q.v.) contains aquatic plants with submerged or floating stems and leaves. The flowers are solitary, as in Anemone Pulsatilla (Pasque flower) and the wood
pheasant
series of perianth leaves, which are petaloid and attractive in Anemone where honey is secreted by modified stamens, as in A. Pulsatilla, or, as in A. nemorosa (wood
The order falls into several distinguished by characters of well-defined tribes which are the flower and fruit; all are c9s''- -ski slightly coloured and the flower is wind-pollinated (T. minus) or visited for its pollen. In Ranunculus and Adonis a calyx of green protective sepals is succeeded by a corolla of showy petals; in Ranunculus (fig. so) there is a basal honey-secreting gland which is absent in Adonis. In Anemone the achenes bear the persistent naked or bearded style which aids in dissemination; the same purpose is served by the prickles on the achenes of Ranunculus arvensis.Tribe IV. Clematideae comprise the genus Clematis (q.v.), characterized by its shrubby, often climbing habit, opposite leaves and the valvate, not imbricate as in the other tribes, aestivation of the sepals. The usually four sepals are whorled and petaloid, the numerous stamens and carpels are spirally arranged; the flowers are visited by insects for the sake of the abundant pollen. The fruit consists of numer- ous achenes which are generally prolonged into the long feathery style, whence the popular name of the British species, old man's beard (Clematis vita/ha). The genus, which contains about 170 species, has a wide distribution, but is rarer in the tropics than in temperate regions. Special
Baneberry
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