The EquisetumSpecies (Horsetails) of the British Isles
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). • E. variegatum: Eng. Bot. 1897 (1886). • E. variegatum var. wilsonii: Sowerby and Johnson (1859). • E. variegatum var. wilsonii: Eng. Bot. 1898 (1886). • 10 British Equisetum species and hybrids: Sowerby and Johnson, 1863.
To view the illustrations with detailed captions, go to the interactive key. This also offers 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.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2004 onwards. The Equisetum species (horsetails) of the British Isles. Version: 7th March 2015. http://delta-intkey.com’.