(Asch. & Magnus) Kitam.
Description
Circaea alpina subsp. imaicola (Asch. & Magnus) Kitam. is the Asian montane race of the circumboreal enchanter's nightshade complex, distributed according to GBIF across China, Taiwan, the Himalaya (India, Nepal, Pakistan), Myanmar, Thailand, Vietnam, Japan and Korea. It is a delicate herb of cool, moist, shaded habitats: damp coniferous and mixed forest floors, mossy banks, stream sides and humus-rich rocky places, typically between about 2,000 and 3,800 m. The September record from Gaushon in Garhwal, India, at 3,100 m reflects its occurrence in the shaded understorey of temperate Himalayan forest, where it grows in moist leaf litter amongst ferns and bryophytes.
The plant is a slender, glabrous to sparsely pubescent perennial spreading by thread-like, often tuber-tipped stolons, with erect stems usually only 5–25 cm tall. The leaves are opposite, thin, ovate to broadly cordate-ovate, with shallowly toothed margins and a translucent texture. The tiny flowers are borne in a lax terminal raceme that elongates in fruit; each flower has two white, deeply notched (bifid) petals, two sepals and two stamens, in the characteristic two-merous floral plan of Circaea. The small, club-shaped fruit is an indehiscent nutlet covered with soft, hooked bristles that promote epizoochorous dispersal.
Within the Circaea alpina complex, subspecies imaicola is distinguished by features of stolon, leaf shape and fruit, and it represents the principal Himalayan and East Asian element of this widespread, taxonomically intricate species. As a shade-demanding mesophyte it is a reliable indicator of humid, undisturbed montane forest. Circaea itself is of phylogenetic interest as one of the few temperate woodland genera in the otherwise largely tropical and warm-temperate Onagraceae.
Author: (Asch. & Magnus) Kitam. · Sources: POWO (Kew), GBIF, Flora of China Vol. 13, Flora of Pakistan (Onagraceae), Boufford: The Systematics of Circaea (Annals of the Missouri Botanical Garden)