Alyssum minimum Willdenow, Sp. Pl. 3: 464. 1800, p.p., not Linnaeus (1753); A. desertorum var. himalayense T. R. Dudley; A. desertorum var. prostratum T. R. Dudley; A. turkestanicum Regel & Schmalhausen var. desertorum (Stapf) Botschantzev; Psilonema minimum Schur.
Herbs annual, (2-)5-18(-28) cm tall, canescent throughout (except fruit) with appressed, sessile, 8-20-rayed stellate trichomes. Stems erect, ascending, or decumbent, often several from the base. Cauline leaves subsessile or lowermost attenuate to petiolelike base to 5 mm; leaf blade linear to oblanceolate-linear, (0.3-)0.5-2.5(-3) cm × (0.5-)1-3(-4) mm, gradually smaller upward, base attenuate, apex acute. Fruiting pedicels ascending or subdivaricate, (1-)1.5-3.5(-4.5) mm, stout, straight, covered with stellate trichomes only. Sepals oblong, 1.4-1.8(-2) × 0.4-0.5 mm, deciduous, stellate. Petals pale yellow, oblanceolate, 2-2.5 × 0.5-0.6 mm, sparsely stellate outside, caducous, base attenuate, apex obtuse or retuse. Filaments 1-1.8(-2) mm; median pairs gradually expanded from apex to narrowly winged base, not toothed; lateral pair with a broadly winged appendage apically notched into 2 teeth; anthers ovate, 0.1-0.2 mm. Ovules 2 per locule. Fruit orbicular, 2.5-4(-4.5) mm in diam., apex shallowly emarginate; valves not veined, uniformly inflated at middle, broadly flattened at margin, glabrous and often glaucous; style 0.3-0.7 mm, slender, glabrous. Seeds often 2 per locule, ovate, 1.2-1.5 × 0.9-1.1 mm, slightly compressed, margined or not. Fl. and fr. Apr-Jun. 2n = 32.
Deserts, rocky areas; near sea level to 2600 m. Xinjiang, Xizang [Afghanistan, India, Kashmir, Kazakhstan, Mongolia, Pakistan, Russia, Tajikistan, Turkmenistan, Uzbekistan; Europe; naturalized in North America].
Dudley (Notes Roy. Bot. Gard. Edinburgh 24: 157-165. 1962) divided Alyssum desertorum into three varieties distinguished largely on the basis of minor differences in fruit trichomes. In the present authors' opinion, these varieties do not seem to merit recognition. The occurrence in Xizang of this species, which was not recorded in Fl. Xizang. (vol. 2. 1985), is based on the holotype of var. himalayense, Hügel 1191 (W).
