Periandra caespitosa Cambessèdes, Voy. Inde: 27. 1836; Arenaria caespitosa (Cambessèdes) Kozhevnikov; A. rupifraga (Karelin & Kirilov) Fenzl ex Ledebour; Bryomorpha rupifraga Karelin & Kirilov; Thylacospermum rupifragum (Karelin & Kirilov) Schrenk.

Cushions ± semiglobose to nearly mat-forming, glabrous, 30--50 cm in diam. Stems very densely branched, 2--6 cm tall. Leaf blade ovate-lanceolate, 2--4 × ca. 2 mm, rigid, glossy, base joined to sheath, margin ciliate, apex mucronate. Flowers ca. 4 mm in diam. Sepals green, lanceolate, ca. 2.5 × 1 mm, 3-veined, apex obtuse or acuminate. Petals ovate-oblong, margin entire. Disc yellow, orbicular, fleshy. Stamens shorter than sepals. Capsule glossy yellow, globose, 2.5--3 mm. Seed light brown, ca. 1.5 mm. Fl. Jun--Jul, fr. Jul--Aug.

This is one of the most prominent high-alpine cushion plants.

Exposed level or gently sloping stony areas, often in rock crevices; (3600--)4300--6000 m. Gansu, Qinghai, Sichuan, Xinjiang, Xizang [NW India, Kazakhstan, Kyrgyzstan, Nepal, Sikkim].