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 50–140 cm high; 2–12 mm in diameter; erect; slightly rough; bearing whorls of slender branches at the nodes; dying down in autumn. The main stem internodes 10–30 grooved; grooves fine, the ribs between them not prominent. The main stem internodes with a central hollow; central hollow much less than half the diameter of the internode to about half the diameter of the internode (1/3 to 1/2); endodermis surrounding the individual vascular bundles. The main stem sheaths green; loose (the upper sheaths with dilated mouths); 10–30 toothed (as many as the grooves). The teeth not ribbed; appressed, black tipped. The primary branching symmetrical to asymmetrical (?). The primary branches numerous; ascending; simple (slender, ascending). The primary branch internodes 5 -angled (with 4 or five subulate, green or blackish teeth). The primary branch sheaths 4–5 toothed (?). The first branch internodes much shorter than the subtending sheaths to at least as long as the subtending sheaths, at least on the upper parts of the stem. The primary branch internodes hollow. Stomata not sunken.
The cones 0.5–1 cm long; blunt. Spores abortive.
Comments. Stems more deeply grooved than in E. fluviatile, with twice the number of green bands, and more branches.
Distribution. Occurring sometimes, and then often abundant, where both parent species are present.
Classification. Subgenus Equisetum; Section Aestivalia; = E. arvense × E. fluviatile.
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: 21st June 2009. http://delta-intkey.com’.