Osmunda lunaria Linnaeus, Sp. Pl. 2: 1064. 1753; Botrypus lunaria (Linnaeus) Richard.

Rhizomes short, erect, annually producing 1 frond 5-15 (-25) cm tall. Common stipe greenish, cylindrical, 4-12 cm, 2-3 mm in diam., hollow, succulent. Sterile lamina pinnate, sessile, broadly lanceolate or oblong, 3-8 × 1.5-2.5 cm, fleshy, leathery, glabrous, apex rounded or blunt; pinnae 4-6 pairs, approximate, often overlapping, opposite or almost opposite, flabellate (fan-shaped), lunate, or reniform, 1-1.5(-2) cm long and wide, shortly stalked to almost sessile, lowest 1 or 2 pairs 1-2 cm apart, margin entire, crenate, or incised; veins free, flabellately forked, glabrous. Sporophore with stalk 4-7 cm, glabrous; panicle 2- or 3-pinnate, racemose, 3-6 × 1.5-2 cm, glabrous; sporangia sessile, large, 0.5-1 mm in diam. Spores yellowish, surface verrucose. 2n = 90.

Throughout the range of Botrychium lunaria, sporadic plants have been found with incised sterile pinnae and which have been named as forms or varieties, such as B. lunaria f. subincisum Roeper and B. lunaria var. onondagense (Underwood) House.

Reviewer Don Farrar notes that North American authors recognize five taxa within the Botrychium lunaria complex, nearly all of which extend into the Aleutian Islands and thus could extend into Asia. As well, the reported spore size of up to 48 microns might suggest that B. lunaria belongs to the allotetraploid species B. yaaxudakeit Stensvold & Farrar.

The following taxon is excluded from the present treatment, pending further research: Botrychium lunaria var. przevalskii Tzvelev (Novosti Sist. Vyssh. Rast. 36: 17. 2004).

Grasslands, meadows, forests; 1300-4000 m. Gansu, Hebei, Heilongjiang, Henan, Hunan, Jilin, Liaoning, Nei Mongol, Qinghai, Shaanxi, Shanxi, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan [Asia, Australia, N Europe, North America, Pacific islands].