Equisetum Equisetum, L.

1. E. hyemale L. View in CoL , Sp. PI. 1062 (1753).

Stem 30-100 cm x 4- 6 mm, persistent, simple; ridges with 2 rows of tubercles; grooves 10-30; sheaths about as long as broad, whitish with a black band at top and bottom; teeth as many as grooves, very soon caducous; central hollow | or more diameter of stem.

Cone 8-15 mm. 2n —c. 216. Most o f Europe, but rare in the Mediterranean region. All except Az Bl Fa Sa Sb Si.

The following hybrids, both of which have abortive spores, occur locally, sometimes in the absence of the parents. E. x moorei Newman, Phytologist 5; 19 (1854) ( E. occidentale (Hy) Coste ) is like 1 but has more slender, not persistent stems, ridges with irregular tubercles or cross-bands, and the teeth of leafsheaths more persistent. It is possibly E. hyemale x ramosissimum . E. x trachyodon A. Braun, Flora (Regensb.) 22: 305 (1839) is intermediate between E. hyemale and E. variegatum , its probable parents.