DIDYMOCALYX Fröderström, 1942

Synonym : Sedum froderstromii  Hamet ex Fröderström (1942) (nom. inval., Art. 34.1a).

Etymology : Gr. 'didymos' = twice, double, and Gr. ‘calyx’ = calyx; referring to the double whorl of sepals.

Distribution : China (W Sichuan); alpine grasslands, rock crevices, 4400 – 4700 m.

Description (by 't Hart & Bleij in IHSP, 2003) :

Tiny basally branched annual herbs 1 – 2 cm tall.

Leaves subovate to oblanceolate, obtuse, 3 – 5.5 mm.

Flowering branches branched from the base, divergent.

Inflorescences 1- to 3-flowered, bracts oblanceolate, 4 – 5 mm.

Flowers 5-merous, sepals 8 to 10 in 2 alternating whorls, basally free, shortly spurred, subovate to broadly oblanceolate, subacute to obtuse, ± 5 mm, petals free, oblong, obtuse, narrowing to the base, yellow,  ± 5.5 mm, nectar scales linear, obtuse with slightly dilatated tip, styles rather long, fruit divergent, turgid, many-seeded, seeds subovoid, reticulate-papillose.

The 2 whorls of sepals of this species are unique within the family and the feature needs further study.