Diversity: A large family with over 3,700 species in about 330 genera - all herbaceous, many weedy annuals, but also perennials and biannuals. The ethnoflora includes structural variants of Brassica oleracea (cabbage, cauliflower, broccoli, brussels sprouts, kohlrabi, and kale) that represent a classic example of shoot polymorphism resulting from strong (human) selection. The storage or tuberous roots of radish (Raphanus sativus) and horseradish (Armoracia rusticana) are also important, as is the seed of several Brassica species for the production of spice (mustard) and oil.
Distribution: Throughout temperate parts of the World with maximum diversity in the Mediterranean region which has served as a point of origin for many weeds and cultigens of the family that are now widely distributed. The Texas flora includes 48 genera and 135 species and, in terms of species diveristy, this family ranks as number 6 in Texas.
Significant features: Most taxa of the Brassicaceae share a suite of glycosinolate compounds knows as 'mustard oils' that produce the pungent odor that one associates with 'cole' crops, such as cabbage and broccoli, and this can be useful for family recognition. However, the floral structure of this large and diverse family is quite distinctive, as are the fruits. The perianth is biseriate with each whorl, the calyx and corolla, four-parted with no connation. The petals are usually positioned opposite one another and, on face view, the corolla forms a cross ('Cruciferae' = 'cross former'). The stamens are often tetradynamous and the fruit is a bilocular capsule that appears to be derived, like other floral whorls, from a four-parted ancestry that followed an evolutionary path similar to that depicted (redrawn from G. H. M. Lawrence, Taxonomy of Vascular Plants) below:
Whatever the specific process, the resulting gynoecium of the Brassicaceae is bilocular with an unusal septum - the replum - that is probably derived from ancestral carpels. The replum is an excellent key character for the family because it tends to remain attached to the pedicel after fruit dehiscence. Many taxa of the family also show a comon inflorescence type, a standard raceme.
mustard (Brassica nigra) - overview - from Kohler's
Lesquerella argyraea - at anthesis
|Lesquerella densiflora - fruit prior to dehiscence|
|Lesquerella densiflora - fruit dehisced, seeds released - repla remain|
|Lepidium virginicum inflorescence (left - a typical raceme) and infructescence (right - with repla)|
More information on the Brassicaceae