Family Brassicaceae

Family Brassicaceae (also historically called Cruciferae, from the cross-shaped arrangement of its petals) is a family of herbs widely distributed in temperate and subtropical regions, including several plants of major food and oilseed importance -- mustard is commonly used as the representative plant to illustrate the family's characters.

Vegetative characters. Plants are typically herbs (rarely shrubs), with alternate, simple leaves (occasionally pinnately lobed), generally without stipules; the leaves may be arranged in a basal rosette in some species.

Floral characters. The inflorescence is usually a raceme. The flower is actinomorphic and bisexual. The calyx has four sepals, arranged in two whorls of two (the two whorls sometimes described as being at slightly different levels). The corolla is the family's most immediately recognisable feature: exactly four free (polypetalous) petals, each with a narrow basal claw and a broader outer limb, arranged so that, viewed from above, they form a distinct cross shape -- the cruciform corolla that gives the family its older name, Cruciferae. The androecium consists of six stamens in a uniquely diagnostic arrangement called tetradynamous: four of the stamens are longer, and two are noticeably shorter, a pattern found in this family and not in any of the other families covered in this chapter. The gynoecium is bicarpellary (two carpels) and syncarpous, with a superior ovary that begins its development as a single chamber but becomes divided into two chambers by the later growth of a thin, membranous false partition called the replum, running down the middle; the ovules are borne not on this replum but on the ovary's own wall, a placentation type called parietal.

Fruit. This precise ovary structure is reflected directly in the fruit: Brassicaceae typically produces a siliqua, a long, narrow, two-chambered dry fruit that splits open along both of its outer sutures, releasing two outer valves while the seeds remain attached to the persistent central replum; a shorter, broader version of this same fruit type, found in some genera, is called a silicula. …