15. Equisetum scirpoides Michaux, Fl. Bor.-Amer. 2: 281. 1803.
Dwarf scouring rush, prêle faux-scirpe
Aerial stems persisting more than a year, unbranched, tortuous, 2.5--28 cm; lines of stomates single; ridges 6. Sheaths green proximally, black distally, elliptic in face view, 1--2.5 × 0.75--1.5 mm; teeth 3, dark with white margins, not articulate to sheath. Cone apex pointed; spores green, spheric. 2 n =216.
Cones maturing in summer, or cones overwintering and shedding spores in spring. Wet woods, peat bogs, tundra; 0--1000 m; Greenland; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Idaho, Ill., Iowa, Maine, Mass., Mich., Minn., Mont., N.H., N.Y., S.Dak., Vt., Wash., Wis.; n Eurasia.