7b. Equisetum ramosissimum subsp. debile (Roxburgh ex Vaucher) Hauke, Amer. Fern J. 52: 33. 1962.
笔管草 bi guan cao
Equisetum debile Roxburgh ex Vaucher, Mém. Soc. Phys. Genève 1: 387. 1822; Hippochaete debilis (Roxburgh ex Vaucher) Holub; H. ramosissima subsp. debilis (Roxburgh ex Vaucher) Á. Löve & D. Löve.
Plants medium-sized to large. Rhizome erect or creeping, blackish brown, nodes and roots with numerous long yellowish brown trichomes or glabrous. Aerial stem perennial, monomorphic, green, up to (or more than) 60 cm tall, 3-7 mm in diam. at middle, mature main stem often branched, but often only with few branches; internodes 3-10 cm. Main stem 10-20-ridged; ridges arc-shaped abaxially, with a row of tubercles or small light brown cross grains; sheaths short, lower portion green, upper portion slightly blackish brown; sheath teeth 10-22, narrowly deltoid, teeth on upper portion light brown, membranous, caducous or sometimes persistent, teeth on lower portion blackish brown, leathery, flattened, conspicuously edged laterally, stomatal bands on sheath teeth conspicuous or inconspicuous. Lateral branches hard, cylindrical, 8-12-ridged; ridges with tubercles or cross grains; sheath teeth 6-10, light brown, lanceolate, short, membranous, caducous or persistent. Strobilus shortly clavate or ellipsoid, 1-2.5 cm, 0.4-0.7 cm in diam. at middle, apex with small acute tip, sessile.
Forests, forest margins, under bushes, meadows, banks of rivers and streams; sea level to 3200 m. Anhui, Chongqing, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hainan, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shandong, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [Bangladesh, India, Indonesia, Japan, Laos, Malaysia, Myanmar, Nepal, New Guinea, Philippines, Singapore, Thailand, Vietnam; S Pacific islands (Fiji, New Caledonia, New Hebrides)].
Equisetum ramosissimum subsp. debile is sometimes treated as a species. Based on the examination of a large number of specimens in China, we found that specimens from N, NE, and NW China are typical E. ramosissimum, but those from S, especially SW, China are between E. ramosissimum and E. debile. Therefore, E. debile is better treated as a subspecies.