Capsella

Annuals or biennials; not scapose; mostly pubescent, trichomes sessile and stellate, sometimes mixed with simple or forked ones. Stems erect or ascending, unbranched or branched. Leaves basal and cauline; petiolate or sessile; basal rosulate, petiolate, blade margins pinnately lobed, lyrate, runcinate, or, rarely, entire, dentate, or repand [sinuate]; cauline blade (base sagittate, amplexicaul, or auriculate), margins entire, dentate, or sinuate. Racemes (corymbose, several-flowered), considerably elongated in fruit. Fruiting pedicels divaricate, slender. Flowers: sepals erect or ascending, [ovate-]oblong, (glabrous or pubescent); petals [sometimes absent] usually white or pink [reddish], obovate [spatulate], (much longer or shorter than sepals), claw differentiated from blade, (apex obtuse); stamens tetradynamous; filaments not dilated basally; anthers ovate [oblong], (apex obtuse); nectar glands (4), lateral, 1 on each side of lateral stamen. Fruits silicles, dehiscent, sessile, obdeltoid to obdeltoid-obcordiform, strongly flattened, strongly keeled, angustiseptate; valves (papery), each prominently veined, glabrous; replum rounded; septum complete; ovules (12–)20–40 per ovary; (style included or exserted from apical notch); stigma capitate. Seeds uniseriate, plump, not winged, oblong; seed coat (reticulate), mucilaginous when wetted; cotyledons incumbent. x = 8.

Distribution

Introduced; Europe, Asia, n Africa, introduced also in Mexico, West Indies, Central America, South America, Atlantic Islands, Pacific Islands, Australia.

Discussion

Species 4 (1 in the flora).

The number of species to be recognized in Capsella is controversial, and some authors (e.g., S. Svensson 1983; R. C. Rollins 1993; O. Appel and I. A. Al-Shehbaz 2003) treated the genus as monotypic, whereas others (e.g., H. Hurka and B. Neuffer 1997; P. Nutt et al. 2003) recognized three or four species.

Selected References

Hurka, H. and B. Neuffer. 1997. Evolutionary processes in the genus Capsella (Brassicaceae). Pl. Syst. Evol. 206: 295–316.

Neuffer, B. and H. Hurka. 1999. Colonizing history and introduction dynamics of Capsella bursa-pastoris in North America: Isozymes and quantitative traits. Molec. Ecol. 8: 1667–1681.

Nutt, P. et al. 2006. Capsella as a model system to study the evolutionary relevance of floral homeotic mutants. Pl. Sys. Evol. 259: 217–235.

Slotte, T. et al. 2006. Intrageneric phylogeny of Capsella (Brassicaceae) and the origin of the tetraploid C. bursa-pastoris based on chloroplast and nuclear DNA sequences. Amer. J. Bot. 93: 1714–1724.

Lower Taxa

Capsella bursa-pastoris