Equisetum Equisetum, Ehrh. Equisetum Equisetum, L.

8. E. pratense Ehrh. View in CoL , Hanno ver. Mag. 9; 138 (1784).

Rhizome glabrous. Sterile stems 10-60 cm x 1-2 mm, regularly and

abundantly branched; branches patent or recurved, simple; ridges rough; grooves 8-20; sheaths mostly green; teeth as many as grooves; central hollow at least | diameter of main stem. Fertile stems usually shorter, developing short branches after the spores are ripe; sheaths numerous, yellowish-white, with 10-20 pale teeth. Cone 15-40 mm. 2« = c. 216. N., C. & E. Europe. Au Be Br Cz Da Fe Ga Ge Hb He Is It No Po Rs (N, B, C, W, K, E) Su.

9. E. arvense L. View in CoL , Sp. Pl. 1061 (1753).

Rhizome pubescent. Sterile stems 10-80 cm x (1—)3—5 mm, usually regularly and abundantly branched; branches ascending or suberect, simple; ridges nearly smooth; grooves (4—)6— 19; sheaths green; teeth as many as grooves; central hollow less than diameter of main stem. Fertile stems appearing before the sterile, usually shorter, simple, pale brown, dying after the spores are shed; sheaths 4-6, pale brown, with darker teeth. Cone (4-) 10-40 mm. 2n —c. 216. Throughout Europe. All except Az.

A serious weed in some areas. In small arctic plants, the fertile stems become green, at least below, and branch irregularly after the spores are shed.

10. E. telmateia Ehrh. View in CoL , Hannover. Mag. 18: 287 (1783)

( E. maximum auct., E. majus Gars. ).

Rhizome pubescent. Sterile stems (15-)5O-2OO cm x 10-20 mm, regularly and abundantly branched, ivory-white; branches green, patent, simple; ridges smooth; grooves 20-40, fine; sheaths pale below, dark at top; central hollow at least J diameter of main stem. Fertile stems appearing before the sterile, shorter, simple, pale brown, dying after the spores are shed; sheaths numerous, pale brown, with dark teeth. Cone 40-80 mm. 2n = c. 216. Europe, except the extreme north and most of the U.S.S. R. All except Fa Fe Is No Rs (N, C, E) Sb.

In addition to those mentioned above, six other interspecific hybrids have been reported, but all are rare.

FILICOPSIDA1