4. Diapensia Linnaeus, Sp. Pl. 1: 141. 1753; Gen. Pl. ed. 5, 69. 1754.
Pincushion plant [Greek dia-, composed, and pente, five, alluding to sepal, petal, and stamen numbers]
Guy L. Nesom
Subshrubs, forming tussocks, cushions, domes, or mats, caulescent, taprooted. Stems mostly prostrate to decumbent, branched; branches procumbent or decumbent to erect. Leaves cauline, mostly opposite or compactly whorled, densely imbricate or crowded, 3-15 mm; petiole present or absent; blade oblong-lanceolate to narrowly spatulate, obovate, or spatulate-elliptic, slightly falcate, margins entire, apex acute or obtuse, surfaces glabrous, appearing 1-veined, sometimes with 1-2, indistinct, lateral veins. Inflorescences solitary flowers, pedicellate to subsessile, immediately subtended by 2-3 bracts. Pedicels ebracteate, elongating after anthesis. Flowers: sepals distinct or connate proximally; petals connate in proximal 1/2, corolla cupulate to campanulate, 7-10 mm, lobes white to cream or pinkish tinged to rose, margins entire; anthers 2-locular, without basal spurs, longitudinally dehiscent; filaments adnate to corolla tube; staminodes absent or vestigial. x = 6.
Species 5 (2 in the flora): North America, n Europe, Asia.
The three temperate species of Diapensia are endemic to the Sino-Himalayan Mountains. They differ as a group from the two boreal species by their production of vestigial staminodes (see F. Ludlow 1976).
SELECTED REFERENCE Evans, W. E. 1927. A revision of the genus Diapensia with special reference to the Sino-Himalayan species. Notes Roy. Bot. Gard. Edinburgh 15: 209-236.