6.
Equisetum sylvaticum
Linnaeus, Sp. Pl. 2: 1061. 1753.
Wood horsetail, prêle des bois
Aerial stems dimorphic; vegetative stems brownish to green, branched, 25--70 cm; hollow center 1/6--1/3 stem diam. Sheaths squarish in face view, 3--6 × 2.5--6 mm; teeth reddish, 8--18, papery, 3--10 mm, coherent in 3--4 large groups. Branches in regular whorls, delicate, arching, branched, solid; ridges 3--4; valleys channeled; 1st internode of each branch longer than subtending stem sheath; sheath teeth attenuate. Fertile stems brown, with stomates, initially unbranched, persisting and becoming branched and green after spore discharge. 2 n =216.
Cones maturing in late spring. Moist forests; 0--2800 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, Conn., Del., Idaho, Iowa, Maine, Md., Mass., Mich., Minn., N.H., N.J., N.Y., N.Dak., Ohio, Pa., R.I., S.Dak., Vt., Va., Wash., W.Va., Wis.; Europe; n Asia to ne China, Japan in Hokkaido.
