| | The Equisetum species (horsetails) of Britain and Ireland |
“Mackay’s Horsetail”.
E. mackaii 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 30–100 cm high; 2–4 mm in diameter; erect to decumbent; greyish green; very rough; sparingly branched, the branches solitary and similar to the main stem, or simple; persisting through the winter. The main stem internodes not swollen; 8–12 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 at first green with a black band at the top, but becoming entirely black; 2–4 mm long; appressed. The teeth four ribbed; subulate, usually black; persistent. The primary branches when present, simple. Stomata sunken.
The cones only about 0.5 cm long (often deformed and partly abortive); apiculate. Spores abortive.
Distribution. Iceland, Norway, Upper Rhineland; south-west Greenland; northern temperate North America. Largely confined in the British Isles to Scotland (Aberdeen and Kincardine by the Dee, and Perth), and Ireland (widespread there, but absent from the centre and most of the south-east); on shady banks of lakes and streams.
Classification. Subgenus Hippochaete; = E. hyemale × E. variegatum.
Illustrations. • E. × trachyodon: Sowerby and Johnson (1859). Equisetum × trachyodon A. Br. With (below) details of stem sheaths, and part of the transverse section of an internode. From Sowerby and Johnson (1859). • E. x trachyodon: as E. trachyodon, Eng. Bot. 1896 (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’.
