CRUCIEERAE, a family of flowering plants, which derives its name from the cruciform arrangement of the four petals of the flower. It is a family of herbaceous dicotyledons, many of which, such as wallflower, stock, mustard, cabbage, radish and others, are well-known garden or field-plants. Many are annuals ; among these are some of tt_e commonest weeds of cultivation, shepherd's purse (Capsella Bursa-pastoris), charlock (Brassica Sinapis), hedge mustard (Sisymbrium officinale), Jack-by-the-hedge (S. Alliaria). Others are biennials producing a number of leaves on a short stem in the first year, and in the second sending up a flowering shoot at the expense of the nourishment stored in the thick tap-root dur ing the previous season. Under cultivation this root becomes much enlarged, as in turnip, swede and others. Wallflower (Cheiranthus Cheiri), however, is a perennial. The leaves when borne on an elongated stem are arranged alternately and have no stipules. The flowers are in racemes without bracts ; dur ing the life of the flower its stalk continues to grow so that the open flowers of an in florescence stand on a level (that is, are corymbose). The flowers are regular, with four free sepals arranged in two pairs at right angles, four petals arranged crosswise in one series, and twa sets of stamens, an outer with two members and an inner with four, in two pairs placed in the middle line of the flower and at right angles to the outer series. The four inner stamens are longer than the two outer ; and the stamens are hence collectively described as tetra dynamous. The pistil, which is above the rest of the members of the flower, consists of two carpels joined at their edges to form the ovary which becomes two-celled by subsequent ingrowth of a septum from these united edges; a row of ovules springs from each edge. The fruit is a pod or sili qua splitting by two valves from below up wards and leaving the placentas with the seeds attached to the rep/um or framework of the septum. The seeds are filled with the large embryo, the two cotyledons of which are variously folded. In germination the cotyledons come above ground and form the first green leaves of the plant.
Pollination is effected by insects. The petals are generally white or yellow, more rarely lilac or some other colour, and between the bases of the stamens are honey-glands.
Cruciferae is a large family containing 2 20 genera and about ',goo species. It has a world-wide distribution, but finds its chief development in the temperate and frigid zones, especially of the northern hemisphere, and as Alpine plants. In the subdivision of the family into tribes use is made of differences in the form of the fruit and the manner of folding of the embryo. When the fruit is several times longer than broad it is known as a siliqua, as in stock; when about as long as broad, a silicula, as in shepherd's purse.
The family is well represented in Britain—among others by Nasturtium (N. officinale, water-cress), Arabis (rock-cress), Car damine (bitter-cress), Sisymbrium (hedge mustard), etc.; S. Irio is London rocket (so-called because it sprang up after the fire of London in 1666), Brassica (cabbage and mustard), Diplotaxis (rocket), Cochlearia (scurvy-grass), Capsella (shepherd's purse), Lepidium (cress), Thlaspi (penny-cress), Cakile (sea rocket), Raphanus (radish), and others. Of economic importance are species of Brassica, including mustard (B. nigra), white mustard, used when young in salads (B. alba), cabbage (q.v.) and its numerous forms derived from B. oleracea, turnip (B. campestris), and swede (B. Napus), Raplianus sativus (radish), Cochlearia Ar moracia (horse-radish), Nasturtium officinale (water-cress), Lepidium sativum (garden cress). Isatis affords a blue dye, woad. Many of the genera are known as ornamental garden plants ; such are Cheiranthus (wallflower), Matthiola (stock), Iberis (candy tuft), Alyssum (Alison), Hesperis (dame's violet), Lunaria (hon esty) Aubrietia and others.
In North America the family is represented by about 5o genera, many of the species having been introduced from Europe as weeds, which have become distributed over a wide territory. In the eastern region the largest genera are rock cress (Arabis) and bitter cress (Cardamine) ; while in the western mountain region the largest genus is Whitlow-grass (Draba).