Rapistrum


Rapistrum, the bastard cabbages, is a genus of the family Brassicaceae with a distinctive cross like arrangement of its petals. It is also known as wild-turnip or turnipweed. Species of Rapistrum are annual to perennials. The yellow petals are accompanied by sepals that stand vertically at near right angles. Leaf shape and arrangement varies from rough toothed to a configuration of opposingly lobed pairs along the plant stalk, pinnately lobed.

Etymology

The word "Rapistrum" is formed from the Latin rapa and -astrum,.

Fruit

The genus Rapistrum has a characteristic fruit comprising two segments, one distal and one proximal:
  • The distal is the part of the fruit farthest away from the point of attachment. The distal is endowed with a ribbed spheroid base that tapers to form a narrowed projection. It holds a single seed.
  • The proximal 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.