# 1911 Encyclopædia Britannica/Onagraceae

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​ONAGRACEAE, in botany, an order of dicotyledons belonging to the series Myrtiflorae, to which belongs also the myrtle order, Myrtaceae. It contains about 36 genera and 300 species, and occurs chiefly in the temperate zone of the New World, especially on the Pacific side. It is represented in Britain by several species of Epilobium (willow-herb), Circaea (enchanter’s nightshade), and Ludwigia, a small perennial herb very rare in boggy pools in Sussex and Hampshire. The plants are generally herbaceous, sometimes annual, as species of Epilobium, Clarkia, Godetia, or biennial, as Oenothera biennis—evening primrose—or sometimes become shrubby or arborescent, as Fuchsia (q.v.). The simple leaves are generally entire or inconspicuously toothed, and are alternate, opposite or whorled in arrangement; they are generally exstipulate, but small caducous stipules occur in Fuchsia, Circaea and other genera. The flowers are often solitary in the leaf-axils, as in many fuchsias, Clarkia, &c., or associated, as in Epilobium and Oenothera, in large showy terminal spikes or racemes; in Circaea the small white or red ​flowers are borne in terminal and lateral racemes. The regular flowers have the parts in fours, the typical arrangement as illustrated by Epilobium, Oenothera and Fuchsia being as follows: 4 sepals, 4 petals, two alternating whorls of 4 stamens, and 4 inferior carpels.
| Fig. 1.—Fuchsia coccinea, 1/2 nat. size. 1, Flower cut open after removal of sepals; 2, fruit; 3, floral diagram. | Fig. 2.—Floral diagram of Circaea. |
The floral receptacle is produced above the ovary into the so-called calyx-tube, which is often petaloid, as in Fuchsia, and is sharply distinguished from the ovary, from which it separates after flowering.
In Clarkia the inner whorl of stamens is often barren, and in an allied genus, Eucharidium, it is absent. In Circaea the flower has its parts in twos. Both sepals and petals are free; the former have a broad insertion, are valvate in bud, and reflexed in the flower; in Fuchsia they are petaloid. The petals have a narrow attachment, and are generally convolute in bud; they are entire (Fuchsia) or bilobed (Epilobium); in some species of Fuchsia they are small and scale-like, or absent (F. apetala). The stamens are free, and those of the inner whorl are generally shorter than those of the outer whorl. The flowers of Lopezia (Central America) have only one fertile stamen.
* From Vines’ Students’ Text-Book of Botany, by permission of Swan Sonnenschein & Co.
* Fig. 3.
* A, Young flower of Epilobium hirsutum. c, petals; f, inferior ovary; k, sepals; s, pedicel.
* B, Fruit of Epilobium after dehiscence, w, outer wall; m, columella formed by the septa;   sa, seed with tufts of hairs.
The large spherical pollen grains are connected by viscid threads. The typically quadrilocular ovary contains numerous ovules on axile placentas; the 1-to-2-celled ovary of Circaea has a single ovule in each loculus. The long slender style has a capitate (Fuchsia), 4-rayed (Oenothera, Epilobium) or 4-notched (Circaea) stigma. The flowers, which have generally an attractive corolla and honey secreted by a swollen disk at the base of the style or on the lower part of the “calyx-tube,” are adapted for pollination by insects, chiefly bees and lepidoptera; sometimes by night-flying insects when the flowers are pale and open towards evening, as in evening primrose. The fruit is generally a capsule splitting into 4 valves and leaving a central column on which the seeds are borne as in Epilobium and Oenothera—in the former the seeds are scattered by aid of a long tuft of silky hairs on the broader end. In Fuchsia the fruit is a berry, which is sometimes edible, and in Circaea a nut bearing recurved bristles. The seeds are exalbuminous. Several of the genera are well known as garden plants, e.g. Fuchsia, Oenothera, Clarkia and Godetia. Evening primrose (Oenothera biennis), a native of North America, occurs apparently wild as a garden escape in Britain. Jussieua is a tropical genus of water- and marsh-herbs with well-developed aerating tissue.