The EquisetumSpecies (Horsetails) of the British Isles
The rhizomes often(?) bearing tubers. The shoots all green and alike vegetatively, the sterile and cone-bearing shoots emerging at the same time.
The main stems 10–60 cm high; 1–3 mm in diameter; erect, or decumbent; slightly rough; bearing whorls of slender branches at the nodes (usually, but often irregularly), or sparingly branched, the branches solitary and similar to the main stem, or simple; dying down in autumn. The main stem internodes not swollen; 4–8 grooved; grooves deep, with prominent ridges between. The main stem internodes with a central hollow; central hollow much much less than half the diameter of the internode (small, scarcely larger than the outer canals); endodermis comprising a single layer outside the ring of vascular bundles. The main stem sheaths green; 4–12 mm; loose; 4–8 toothed. The teeth one ribbed; triangular-subulate, blackish, with narrow, whitish-scarious margins; persistent (?). The primary branching symmetrical to asymmetrical (often irregular). The primary branches few to numerous; ascending to spreading; simple (spreading to sub-erect, often short). The primary branch internodes 4–5 grooved; 4–5 grooved. The primary branch sheaths 4 toothed (these short, appressed, black-tipped). The first branch internodes much shorter than the subtending sheaths. The primary branch internodes hollow. Stomata not sunken.
The cones 1–3 cm long; blunt. Spores released May to July.
Distribution. Europe, from Iceland and northern (not arctic) Russia to central Spain and northern Portugal, Sicily, Greece and the Caucasus, temperate Asia; and North America, from Newfoundland and Alaska to Connecticut and Oregon. Common throughout the British Isles, in bogs, fens, marshes and wet heaths, woods and meadows, ascending to nearly 1000 m.
Classification. Subgenus Equisetum; Section Aestivalia.
Illustrations. • E. palustre, fertile stem: Sowerby and Johnson, 1859. • E. palustre, variety: Sowerby and Johnson, 1859. • E. palustre: Eng. Bot. 1892 (1886). • 10 British Equisetum species and hybrids: Sowerby and Johnson, 1863. • E. palustre: details of fertile stem, sporangiophore and spores.
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’.