Hand.-Mazz.
Description
Parnassia longipetala is a perennial herb of the eastern Himalaya and adjacent China; GBIF data, comprising around 85 occurrences, attribute the species principally to China (notably south-western provinces and Xizang), with field records extending into Bhutan. It is a plant of moist alpine and subalpine habitats, growing in wet meadows, grassy seepages, streamsides and among rocks where the substrate remains damp through the growing season. The population photographed at Pele-La in central Bhutan (3000 m, July) is characteristic of its occurrence in the cool, humid pastures and flushes of the eastern Himalaya, flowering during the monsoon-fed summer.
The plant forms a small rosette from a short rootstock, the basal leaves long-petiolate with ovate to cordate, entire blades. The flowering stem is erect, usually bearing a single sessile or shortly clasping cauline leaf below the solitary terminal flower. The flower has five green sepals and five free, white petals; in this species the petals are conspicuously long, narrowed and often fringed or attenuate, giving the epithet. Alternating with the fertile stamens are the characteristic Parnassia staminodes, divided into gland-tipped filaments. The superior to half-inferior ovary develops into a capsule splitting into valves and releasing numerous small seeds.
The family placement given here (Celastraceae) follows the broad APG circumscription, under which Parnassia and its allies (formerly Parnassiaceae) are treated within an enlarged Celastraceae; older floras place the genus in its own family. P. longipetala, described by Handel-Mazzetti, is distinguished within the Himalayan Parnassia complex by its elongate petals and staminode form. Given its restricted documented range and specialised wetland-meadow habitat, the species warrants attention, as such high-elevation flush communities are vulnerable to grazing, drainage and climatic change.
Author: Hand.-Mazz. · Sources: POWO (Kew), GBIF, Flora of China, Flora of Bhutan, Annotated Checklist of the Flowering Plants of Nepal, monograph of the genus Parnassia (Wu & Gu)