Annual to perennial herbs, rarely woody or shrubby. Leaves alternate or spirally arranged, generally simple and exstipulate, basal often rosulate. Hairs usually simple or branched, sometimes appressed or absent.Inflorescence usually racemose, corymbose. Flowers usually hermaphrodite, hypogynous, actinomorphic, pedicellate and ebracteate. Sepals 4, erect-closed to spreading-open, in two decussate pairs, inner sometimes saccate at the base. Petals 4 (very rarely suppressed), alternating with sepals, free, often with distinct claw, usually yellow, white or lilac, cruciform. Stamens 6 (rarely 4, 2 or even 1 due to suppression, very rarely more than 6), tetradynamous, outer pair short and inner 4 long; filaments some-times winged, toothed or appendaged; anthers dithecous (very rarely monothecous) and fertile. Lateral nectar glands (at the base of the two outer short stamens) almost always present and of various shapes; middle glands present or absent. Ovary bicarpellate, syncarpous, 1-2-celled or with 2-many superimposed cells, 1-many ovuled on two parietal placentas; septum false being formed by the placental outgrowths; style simple, sometimes absent; stigma often capitate, entire to bilobed. Fruit short (silicula) or long (siliqua), dehiscent or indehiscent, usually opening from below by 2 valves which often leave the seeds attached to replum and the false septum, sometimes breaking transversely into 1-few seeded cells, rarely seeds also developing in an indehiscent beak below the style or stigma; valves membranous to coriaceous and thick, plane or inflated, sometimes keeled, winged or appendaged, glabrous or hairy, with 1-many parallel veins (generally rnidvein prominent). Seeds 1-many in 1-2 rows, smooth, granular or reticulated, rarely longitudinally striated, sometimes winged, usually mucilaginous when wet, exalbuminous; radicle accumbent (when it is bent round so as to lie along the edges of the cotyledons i.e. embryo pleurorhizus) or incumbent (when it lies on the face of one cotyledon i.e. embryo notorhizus) ; cotyledons narrowly linear to spathulate, sessile or stalked, rarely plicate or conduplicate (longitudinally folded).
A large family of about 350 genera and nearly 3000 species, primarily of the temperate regions and cooler climates. Of these only 92 genera and about 250 species are reported from our area, which includes 5 genera and 14 species known from cultivation only. It is well known for its oil producing seeds.
Taxonomy of this family is primarily based on fruit characters, hence the lack of fruits in herbarium specimens sometimes makes correct identification difficult. O.E. Schulz in Engler, Pflanzenreich, Cruciferae-Brassiceae 70 (IV. 105) :1-290 ;1919) and 84 (IV. 105) :1-100 (1923) ; Cruciferae-Sisymbrieae, 86 (IV, 105) : 1-388 (1924) ; Draba et Erophila 89 (IV. 105) : 1-396 (1927) revised monographically parts of the family, and in Engler & Prantl, Nat. Pflanzenf., ed. 2, 17 b: 227-658 (1936) revised the entire family. Although this work is the only thorough and comprehensive one for the whole family, a revaluation of tribes and subtribes and above all generic concepts, in certain cases, is much needed. Distinction of beak or biarticulation of fruits sometimes become only theoretical and practically indistinguishable; hairy plants sometimes become glabrous or almost glabrous. Efforts are being made to produce groupings or really workable practical keys for the separation of genera, irrespective of their places in the various tribes (P.H. Davis, Fl. Turkey 1: 249-262, 1965; Rechinger f., Fl. Iranica 57: 3-30, 1968). However, the following account of the family, from West Pakistan, is based broadly on the treatment given by O.E. Schulz in the above mentioned publications.
It is difficult to reach and identify a genus following the key for the tribes, therefore a separate key for all the genera, irrespective of their tribes (adapted and modified from K.H. Rechinger, Fl. Iran. 57: 3-30. 1968) is provided separately. Alternate keys for the genera under their tribes are also provided.
Five Tables are provided to show the fruit characters of almost all the taxa included here under various tribes. This should help in following the generic and specific keys.
Stamen length is given in the proportion of short and long stamens (i.e. length of the 2 outer stamens: length of the 4 inner stamens).
Of the 19 tribes recognized by O.E. Schulz (in Engl. & Prantl, Pflanzen f. ed. 2, 17b: 227-658.1936) only 10 are represented in our area.
Acknowledgements: We are grateful to the United States Department of Agriculture for financing this research under P.L. 480. Thanks are also due to Dr. P.H. Davis, Mr. B.L. Burtt, Mr. I.C. Hedge, Dr. P. Botschantzev, Dr. G. Taylor, Dr. K.H. Rechinger, Dr. R.R. Stewart, Dr. S.I. Ali, Prof. E. Nasir, Dr. Kazmi and Dr. Rafique Ahmed for their every possible help.