Epilobium subg. Chamerion Rafinesque, Amer. Monthly Mag. & Crit. Rev. 2: 266. 1818.
Herbs perennial, erect, usually clumped, with shoots from woody caudex or spreading lateral roots. Stems simple or rarely branched, pubescent to subglabrous, hairs always eglandular. Leaves spirally arranged, rarely subopposite or subverticillate, subleathery, basal ones sessile, upper ones usually petiolate; stipules absent; bracteoles absent. Inflorescence a simple raceme or spike, rarely branched. Flowers 4-merous, slightly zygomorphic, strongly protandrous, lacking a floral tube, producing nectar from raised disk at base of style and stamens. Petals pink to rose-purple, rarely white, obcordate or obtrullate, entire. Stamens 8, subequal in single whorl, erect at onset of anthesis, later reflexed; pollen blue or yellow, shed in monads. Style initially deflexed, becoming erect as stigma deflexes; stigma deeply 4-lobed and revolute, receptive on inner surfaces. Fruit an elongate capsule, slender, 4-loculed, loculidical. Seeds many, with terminal coma of silky hairs. 2n = 36, 72, 108.
Eight species: montane to arctic N hemisphere, widespread in Asia and Europe, barely reaching N Africa, and in North America south to the high mountains of C Mexico; four species in China.
The species occur primarily in moist, rocky areas in high-montane regions, with one species (Chamerion angustifolium) more widespread in disturbed, temperate habitats.
Raven (Ann. Missouri Bot. Gard. 63: 326-340. 1977 ["1976"]) divided this group into two subsections under Epilobium sect. Chamaenerion Tausch, elevated to sections by Holub (Folia Geobot. Phytotax. 7: 81-90. 1972), with Chamerion sect. Rosmarinifolium (Tacik) Holub occurring in SW Asia and Europe, and C. sect. Chamerion, the only section found in China, widespread in the N hemisphere. Although sometimes included within Epilobium, Chamerion forms a well-differentiated sister group to that genus, based on both morphological and molecular evidence.
