Aquatic and Wetland Vascular Plants of the Northern Great Plains
1. Equisetaceae, the Horsetail Family
1. Equisetum L. -- Horsetail, scouring rush
7. Equisetum sylvaticum L. -- Wood horsetail
Stems dimorphic, annual, erect. Sterile stem green, densely branched
from the nodes, 3-7 dm tall, mostly 10- to 18-ridged, the ridges usually
with silicaceous spicules; central cavity usually more than 1/2 the stem
diameter; main stem sheaths 5-10 mm long, the teeth coherent in usually
3-5 broad lobes, reddish-brown, 3-5 mm long. Branches rebranched, spreading
to recurved, 4- or 5-angled. Fertile stems as in E. pratense,
except usually having rebranched rather than simple branches; sheaths
10-25 mm long, the teeth fused into reddish-brown lobes 4-15 mm long. Cones
as in E. pratense. Wet or swampy woods; uncommon; ne ND, ne SD and the
Black Hills; (Circumboreal, in N.Amer. s to MD, WV, KY, IA, SD, nw MT, n ID
and s B.C.).