STEMS: with minute tubercles in 1 row along the ridges. TEETH: irregularly persistent. NOTES: See also parent taxon. Banks of streams and rivers, marshy meadows, roadside ditches: Apache, Cochise, Coconino, Gila, Graham, Maricopa, Mohave, Navajo, Pima, Santa Cruz, and Yavapai cos. (Fig. 1B); 900–2600 m (2850–8500 ft); June–Sep; U.S., Can. Mex., Guatemala REFERENCES: G.Yatskievych and M.D. Windham , 2008, Vascular Plants of Arizona: Equisetaceae. CANOTIA 4 (2): 41–45.