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Descurainia Webb. et Berth.

播娘蒿属

Description from Flora of China

Hugueninia Reichenbach, nom. rej.; Sophia Adanson, nom. rej.

Herbs annual or perennial, rarely shrubs. Trichomes short-stalked, dendritic, very rarely simple, sometimes mixed with glandular, clavate papillae. Stems erect or prostrate, simple or branched basally and/or apically. Basal leaves petiolate, withered by flowering, 2- or 3-pinnatisect, rarely 1-pinnate. Cauline leaves similar to basal. Racemes ebracteate or rarely basally bracteate, elongated or not in fruit. Fruiting pedicels slender, divaricate or erect. Sepals oblong or linear, erect or ascending, base of lateral pair not saccate. Petals yellow or rarely creamy white, as long as or longer than sepals; blade obovate or oblanceolate, rarely oblong, apex obtuse; claw obsolete or distinct. Stamens 6, tetradynamous; filaments not dilated at base; anthers oblong, obtuse at apex. Nectar glands confluent, subtending bases of all stamens; median glands present. Ovules 5-100 per ovary. Fruit dehiscent siliques or silicles, linear, oblong, clavate, or rarely elliptic, terete, sessile; valves with a prominent midvein, smooth or torulose; replum rounded; septum complete or perforated, membranous, veinless or with 1-3 longitudinal veins; style absent or rarely distinct and to 1 mm; stigma capitate, entire. Seeds uniseriate or biseriate, wingless, oblong or ellipsoid, plump; seed coat minutely reticulate, usually mucilaginous when wetted; cotyledons incumbent.

The record of Descurainia sophioides (Fischer) O. E. Schulz in FRPS and Fl. Xizang. (2: 410. 1985) is based on misidentified plants of D. sophia. The former species is restricted to Alaska, Canada, and Russia (Far East and Siberia). It is readily distinguished from D. sophia by having clavate glands on the distal parts of the plant and generally shorter fruiting pedicels 2-7(-10) mm. By contrast, D. sophia is completely eglandular and has fruiting pedicels (5-)8-15(-20) mm.

About 40 species: mainly in North and South America (30 species) and Macaronesia (seven species), one species a cosmopolitan weed.


 

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