| | The Equisetum species (horsetails) of Britain and Ireland |
“Variegated Horsetail”.
E. wilsonii Newman
The rhizomes not tuberous. The shoots all green and alike vegetatively, the sterile and cone-bearing shoots emerging at the same time.
The main stems 15–60 cm high; very slender, 1–3 mm in diameter; decumbent (commonly), or erect to decumbent; green; slightly rough (the ridges with two regular rows of minute tubercles); sparingly branched, the branches solitary and similar to the main stem, or simple; persisting through the winter. The main stem internodes not swollen; 4–10 grooved; grooves moderately deep. The main stem internodes with a central hollow; central hollow much less than half the diameter of the internode (about 1/3); endodermis comprising two layers, one outside and the other inside the ring of vascular bundles. The main stem sheaths green, black banded at the top; about 2–4 mm long; rather loose; 4–10 toothed (as many teeth as grooves). The teeth four ribbed; scarious, except for a blackish centre, triangular- or ovate-lanceolate, at first subulate; persistent (but the subulate tip falling). The primary branches if present, simple. Stomata sunken.
The cones 0.5–0.7 cm long; apiculate. Spores released July to August.
Distribution. Arctic and north temperate regions of Europe, Asia and North America, extending from Greenland to the Pyrenees, northern Italy, Thrace, Caucasus, Mongolia, Connecticut abd Oregon. Widespread in the British Isles, on dunes, river banks, wet ground on mountains, etc., ascending to about 500 m in Kerry (var. wilsonii in Kerry only, usually in shallow water).
Classification. Subgenus Hippochaete.
Illustrations. • E. variegatum: Sowerby and Johnson (1859). Equisetum variegatum Schleich. ex Web. & Mohr. With (lower right) details of a sporangiophore and part of the transverse section of an internode. From Sowerby and Johnson (1859). • E. variegatum: Eng. Bot. 1897 (1886). • E. variegatum var. wilsonii: Sowerby and Johnson (1859). Equisetum variegatum, var. wilsonii (Newm.) Milde. With (below) details of an immature cone and adjoining sheaths, part of a stem sheath, and (botton right) part of the transverse section of an internode. From Sowerby and Johnson (1859). • E. variegatum var. wilsonii: Eng. Bot. 1898 (1886). • 10 British and Irish Equisetum species and hybrids: Sowerby and Johnson, 1863. 1701, Equisetum arvense L.; 1702, E. pratense Ehrh.; 1703, E. telmateia Ehrh.; 1704, E. sylvaticum L.; 1705, E. fluviatile L.; 1706, E. palustre L.; 1707, E. hyemale L.; 1708, E. x moorei Newman; 1709, E. x trachyodon A.Br.; 1710, E. variegatum Schleich. ex Web. & Mohr; 1711, E.variegatum var. wilsonii (Newm.) Milde. From Sowerby and Johnson (1863).
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2004 onwards. The Equisetum species (horsetails) of Britain and Ireland. Version: 5th August 2019. delta-intkey.com’.
