Rapistrum, the bastard cabbages,[1][better source needed] is a genus of the family Brassicaceae with a distinctive cross like arrangement of its petals. It is also known[2] as wild-turnip or turnipweed. Species of Rapistrum are annual to perennials (Lifespan from 1 to 2 or more years). The yellow petals are accompanied by sepals that stand vertically at near right angles (erecto-patent). Leaf shape and arrangement varies from rough toothed (dentate) to a configuration of opposingly lobed pairs along the plant stalk, pinnately lobed.
Etymology
The word "Rapistrum" is formed from the Latin rapa ("turnip") and -astrum, ("incomplete resemblance").[3]
Fruit
The genus Rapistrum has a characteristic fruit comprising two segments, one distal and one proximal:
The distal (upper division) is the part of the fruit farthest away from the point of attachment. The distal is endowed with a ribbed spheroid base (globose) that tapers to form a narrowed projection. It holds a single seed.
The proximal (lower division) is the part of the fruit nearest to the point of attachment. Possesses a more uniform narrower shape compared to the distal above, giving the fruit a waist. It holds a maximum of three seeds, more commonly none or one.
The fruit varies between species in the genus. The distal of R. rugosum is strongly ribbed and narrows to form a beak whereas R. perenne is comparatively less wrinkled and ends with a style that stubbornly resists detachment, 'a persistent style'.
When ripe the distal breaks away in an across-wise fashion, breaking transversely.
^USDA, NRCS (n.d.). "Rapistrum". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 18 October 2015.
^"Rapistrum". Flora North America. Retrieved 2024-09-12.
^Warwick, Suzanne I. "Rapistrum". Flora North America.
