Equisetum ×mackaii
Phytologist 1: 369. 1843 (Nov. 1842.
Basionym: Equisetum hyemale var. mackaii Newman Phytologist 1: 305. 1843 (Sept. 1842)
Synonyms: Equisetum hyemale subsp. trachyodon A.Braun Equisetum ×trachyodon Schleicher ex F. Weber & D. Mohr Equisetum variegatum var. jesupii A.A. Eaton
Treatment appears in FNA Volume 2.
Aerial stems persisting more than a year, unbranched, 20–86 cm; lines of stomates single; ridges 7–16. Sheaths black or black-girdled and white distally, appressed, elongate, 3.5–8 × 2–5.5 mm; teeth 7–16, centers dark, margins white, prominent, not articulate, tip usually brown, long, filiform. Cone apex pointed; spores white, misshapen.
Phenology: Cones maturing in late summer, but misshapen spores not shed.
Habitat: Lakeshores, riverbanks, marshes
Elevation: 0–500 m
Distribution
Greenland, B.C., N.B., Nfld. and Labr. (Nfld.), Ont., Que., Sask., Conn., Ill., Ind., Maine, Mich., Minn., Mont., N.H., N.J., N.Y., Ohio, Oreg., Vt., Wis., n Europe.
Discussion
The hybrid between Equisetum hyemale and E. variegatum, E. × mackaii, is often mistaken for small forms of E. hyemale. I have not seen specimens for the reports from Connecticut and New Hampshire.
Selected References
None.
Lower Taxa
None.