Sisymbrium thomsonii Hook. f.
Perennial, (10-) 20-40 (-60) cm tall, erect, simple or branched from the base, often densely pubescent with simple and branched hairs, rarely almost glabrous. Radical leaves rosulate, spathulate or oblong-obovate, 20-50 (-60) mm long, 6-15 mm broad, shortly stalked, deeply toothed to almost entire, obtuse; cauline leaves many lanceolate or oblong-ovate, sessile, auricled at base, amplexicaul, usually dentate, much smaller than the radical leaves; all leaves densely pubescent or canescent. Racemes 20-40-flowered, ebracteate, rarely few (1-4) bracteate below, up to 20 cm long in fruit. Flowers c. 4 mm across, white or pinkish; pedicels usually 10-15 mm long in fruit, spreading, filiform. Sepals c. 2.5 mm long. Petals 3-5 mm long, 1-1.5 mm broad. Stamens 2: 2.5 (-3) mm long; anthers c. 0.5 mm long. Siliquae 20-45 mm long, 1-1.5 mm broad, usually erect on ± spreading pedicels, terete-compressed; valves prominently mid-veined, glabrous; style c. 1 mm long with a depressed stigma; septum not veined; seeds 20-40 in each locule, c. 1 mm long.
Fl. Per.: May July.
Type: Altai "Hab. in insulis atque ripis if. Tschuja" (LE).
Distribution: C. Asia, Himalayas, Pakistan and Afghanistan.
A very variable species in hairiness, stature and flower size. Its variety griffithiana (Boiss.) Schulz, with slightly larger flowers but glabrous habit, reaches very close to Arabidopsis pterosperma Edgew., with which it may sometimes be confused, but its smaller flowers, smaller seeds without any margin (wing) and softer hairs are distinctive.