Rapistrum

Rapistrum, the bastardcabbages,[1] is a genus of the family Brassicaceae with a distinctive cross like arrangement of its petals. 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.

Rapistrum
Rapistrum rugosum
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Brassicales
Family: Brassicaceae
Genus: Rapistrum
Crantz
Species

Rapistrum rugosum (L.) All
Rapistrum perenne (L.) All

Fruit

The genus Rapistrum has a characteristic fruit comprising two segments:

a) The distal (upper division) 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.

b) The proximal (lower division) 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 from species to species. 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.

References
  1. "Rapistrum". Natural Resources Conservation Service PLANTS Database. USDA. Retrieved 18 October 2015.
  • Stace, C. (1999), Field flora of the British Isles, Cambridge: Cambridge University Press, ISBN 0-521-65315-0.
  • Streeter, D. (1983), The wild flowers of the British Isles, London: Midsummer Books Ltd., ISBN 1-900732-03-3.
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