Arabis bijuga G. Watt

The absence of flowers the species is distinguished from Arabis amplexicaulis Edgew., by its short stellate hairs, like those in In tArabis pangiensis Watt.

The type specimens of A. bijuga Watt and Arabis pangiensis Watt are from the same place (Pangi, Chamba) in N.W. Himalaya, and look remarkably distinct from each other; but are they actually different or just two extreme forms of the same taxon ? This doubt arises because of the following reasons: 1. They are from the same place, 2. There are specimens, with short stellate hairs on leaves like those in the latter species but habit like that of the former species 3. They both grow on rocks, the former on open rocks, and the latter perhaps in rock crevices. This may be the reason of the former being tall and less hairy, and the latter short and more hairy. This type of variation is not uncommon in other species of Arabis. Elsewhere also such forms have been noticed where species are highly polymorphic and variable, and unless we know the entire range of variations, nothing can be said with certainty with the help of the type specimens only. 1 have a feeling that both the above taxa belong to one single species, and this view is supported by the presence of intermediate specimens, all having similar hairs, usually short and branched or stellate, from subglabrous to densely hairy conditions, and their leaves are usually narrow. Thus they are remarkably a distinct group from that of Arabis amplexicaulis Edgew., where the plants usually have longer, simple, forked or branched hairs and somewhat broader leaves.

The A. pangiensis- Arabis bijuga complex problem can only be solved with further experimental works with freshly collected seeds. Arabis amplexicaulis and A. bijuga have often been confused and the latter sometimes wrongly identified, because of its similar habit.

Arabis bijuga, which was previously thought to be restricted to Kashmir and Pakistan, is recorded here for the first time from China. The records from Sichuan are based on Soulié 1493 (P) and the type collection of A. macrantha, Fang Wen-pei et al. 12402 (NAS, SZ); the record from Yunnan is based on Yü 8456 (BM), Forrest 20147 (E, US), and Forrest 16192 (E).

The type collection of Arabis bijuga is basically indistinguishable from those of A. macrantha and A. pangiensis except for being glabrescent (vs. moderately to densely tomentose). However, this difference alone does not justify the recognition of more than one species.

Perennial, 15-40 cm tall, subglabrous to hairy with short branched, somewhat stellate hairs. Radical leaves like in the above species; cauline leaves narrow, oblong, sometimes narrowed at the base also, 1-3 cm long, 2-6 (-8) mm broad, sessile, semi-amplexicaul. Flowers usually large, c. 1 cm across, often with diverging pairs of c. 14 mm long petals; pedicels usually elongated, up to 20 mm long, spreading. Siliquae and seeds as in the previous species.

An intermediate species between A. amplexicaulis Edgew. and A. pangiensis Watt, and forms reaching both sides occur especially when the plants are somewhat glabrous and densely hairy respectively.

Differs from A. amplexicaulis by its slightly larger flowers (with petals c. 14 mm long) short stellate hairs, and narrow cauline leaves; also differs from Arabis pangiensis by its larger stature including flowers, and usually with several cauline leaves.

Herbs perennial, 15-40 cm tall, often densely tomentose or pilose, with primarily short-stalked, stellate trichomes, these sometimes mixed with much fewer, simple or forked ones, rarely plants glabrescent and trichomes restricted primarily to leaf margins. Stems erect, often branched at base. Basal leaves rosulate; petiole 0.5-5 cm; leaf blade obovate-spatulate, oblong, elliptic, or oblanceolate, 1.5-5 × 0.5-1.5 cm, base attenuate, margin dentate or entire, apex obtuse or rounded. Middle cauline leaves sessile, oblong-linear, narrowly elliptic, or narrowly lanceolate, 1-4(-5.5) cm × 2-8 mm, base obtuse or auriculate, margin dentate or entire. Racemes ebracteate. Fruiting pedicels divaricate or ascending, (0.8-)1.2-2.4(-3) cm, slender, straight, glabrous. Sepals oblong, 3.5-5 × 1.2-1.8 mm, glabrous, lateral pair saccate. Petals white or pinkish, oblong or narrowly oblanceolate, 0.9-1.4 cm × 2-4 mm, apex obtuse. Filaments 5-8 mm; anthers oblong, 1-1.5 mm. Ovules 40-70 per ovary. Fruit 3-6 cm × 1-1.2 mm; valves with a prominent midvein extending full length, slightly torulose, glabrous; style 1-1.5 mm. Seeds brown, oblong, ca. 1.2 × 0.5 mm, uniseriate, narrowly winged apically. Fl. Apr-Jun, fr. May-Jul.

Distribution: N.W. Himalaya and Pakistan. Fl. Per.: May-July.

Sichuan, Yunnan [Kashmir, Pakistan].

Grassy slopes, rock crevices, dry cliffs, stony pastures; 2400-3000 m.

Arabis macrantha C. C. Yuan & T. Y. Cheo; A. pangiensis Watt.

Arabis bijuga là một loài thực vật có hoa trong họ Cải. Loài này được Watt mô tả khoa học đầu tiên năm 1881.