Circaea alpina subsp. imaicola (Aschers. & Magnus) Kitam.

Flowering from June to September; fruiting from August to November.

Circaea alpina subsp. imaicola is close relative of Circaea alpina subsp. angustifolia, but differs from the latter in its leaves ovate (vs. elliptic to trullate), base rounded to subcordate, rarely broadly cuneate (vs. narrowly to broadly cuneate).

Circaea alpina subsp. imaicola is occurring in Anhui, Gansu, Guizhou, Henan, Hubei, Jiangxi, Qinghai, Shaanxi, Shanxi, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang of China, NE Afghanistan, Bhutan, India, N Myanmar, Nepal, Thailand, NW Vietnam.

Circaea (Onagraceae), a genus of seven species from the northern hemisphere, forms a monophylctic group defined by the following synapomorphies: two stamens (opposite the sepals), fruits indehiscent capsules, hooked hairs on the fruits, and perianth parts reduced to two. A cladistic analysis of the genus was performed using characters from morphology, anatomy and palynology. Results of the cladistic analysis support all six subspecies of Circaea alpina (single-seeded fruits, stolons terminated by tubers, and viscin threads reduced or absent) and C. repens form a monophyletic clade (Boufford et al., 1990).

Plants 3.5-45 cm tall. Stem densely to sparsely pubescent. Leaves ovate to broadly ovate, less commonly orbicular-ovate, 2-7 cm long, 1.4-4.5 cm wide, base truncate or rounded, less often broadly cuneate to subcordate, margin subentire to occasionally prominently dentate, apex acute to shortly acuminate. Inflorescence simple or branched, pubescent with short glandular hairs, less commonly glabrous; flowering pedicel erect or ascending, glabrous; flowers clustered at apex of raceme and opening before elongation of raceme axis, with a minute setaceous bracteole at base. Buds glabrous, rarely glabrescent; ovary with uncinate hairs at anthesis; floral tube nearly absent to 0.3 mm. Sepals oblong to ovate, apex rounded to obtuse. Petals white or pink, narrowly to broadly obovate in outline, apical notch 1/4-1/2 length of petal; petal lobes rounded. Uncinate hairs of fruit unpigmented.

The chromosomal number of Circaea alpina subsp. imaicola is 2n = 22 (Seavey and Boufford, 1983).

Growing in cool moist places along streams, thickets, deciduous and coniferous forests in mountains; 2000-4000 m.