1. Equisetum diffusum D. Don, Prodr. Fl. Nepal. 19. 1825.
披散木贼 pi san mu zei
Equisetum diffusum var. paucidentatum C. N. Page; E. mekongense C. N. Page.
Plants small to medium-sized. Rhizome creeping, erect, or ascending, blackish brown, nodes and roots with dense long yellowish brown trichomes or glabrous. Aerial stems annual, monomorphic, 10-30(-70) cm tall, 1-2 mm in diam. at middle, much branched; internodes 1.5-6 cm, green but those of lower 1-3 nodes blackish brown, not lustrous. Main stem 4-10-ridged; each side of ridge raised and forming edges reaching lower sheath teeth; each edge with a row of tubercles reaching sheath teeth; sheath tubes long, narrow, grayish green in lower portion, blackish brown in upper portion, with a deep groove going through back of sheath; sheath teeth 5-10, blackish brown, lanceolate, leathery, caudate at apex, persistent. Lateral branches slender, rigid, terete, 4-8-ridged; each side of ridge with edges and tubercles; sheath teeth 4-6, grayish green, deltoid, leathery, persistent. Strobilus terete, 1-9 cm, 4-8 mm in diam., apex blunt; stalk prolonged when mature and 1-3 cm.
Under bushes, roadsides; sea level to 3400 m. Chongqing, Gansu, Guangxi, Guizhou, Hunan, Jiangsu, Sichuan, Xizang, Yunnan [Bhutan, NE India, Japan, Kashmir, Myanmar, Nepal, Pakistan, Vietnam].
Equisetum ×wallichianum C. N. Page (Fern Gaz. 11: 34. 1975), possibly a hybrid between E. diffusum and E. arvense, was described from China (possibly W Sichuan) and is said to be distributed in India and Nepal.