ROBERTSIANUM Alexander, 1936

Synonym : Sedum parvum ssp. robertsianum  (Alexander) R. T. Clausen (1981)

Distribution : USA (Texas : Brewster County), adjacent Mexico (Coahuila) ; shallow calcareous soil, ± 1300 m.

Description (according to IHSP, 2003) :

Glabrous perennial herbs with caespitose fleshy stems, branched at the base, with numerous decumbent branchlets 8 - 12 cm long.

Leaves alternate, ovoid, apiculate, appearing minutely papillose (caused by reflection of the inner facets of windowed cells), turgid, 5 - 8 mm, 3 - 4 mm wide and thick, yellow-green.

Inflorescences : Flowering branches erect, axillary, inflorescences cymes, simple or with 2 branches, sometimes with short branches at the base with solitary flower, bracts leaf-like but much smaller.

FIowers 5- (rarely 4-) merous, sessile or subsessile, sepals unequal, the 2 outer much larger than the inner, lanceolate, ± 2 mm, petals lanceolate, canaliculate, ± 4 mm, bright yellow.

Cytology : 2n = 28

According to Charles Uhl, this species is only distantly related to S. parvum and should not be included in the synonymy of this species as IHSP suggests (Rhodora 87, 1985).