Equisetum arvense Linnaeus

Desjardins, Émilie, Lai, Sandra, Payette, Serge, Dubé, Martin, Sokoloff, Paul C., St-Louis, Annie, Poulin, Marie-Pier, Legros, Jade, Sirois, Luc, Vézina, François, Tam, Andrew & Berteaux, Dominique, 2021, Survey of the vascular plants of Alert (Ellesmere Island, Canada), a polar desert at the northern tip of the Americas, Check List 17 (1), pp. 181-225 : 199-200

Equisetum arvense Linnaeus

Syn.: Equisetum arvense subsp. alpestre (Wahlenb.) Schönswetter & Elven

Materials examined. CANADA – Nunavut • Ellesmere Island, CFS Alert ; 82°28′22″N, 062°36′20″W; 78 m a.s.l.; 17 Jul. 2019; habitat: xeric on the margins of a river inside a creek; QFA0634994 .

Identification. Plants 2–7 cm high; herbaceous; not caespitose. Fibrous roots and rhizomes present. Rhizomes black or reddish-brown. Vegetative stems 2–7 cm long; annual; ascending or decumbent; green or yellowish-green;

simple or branched from the whorls (branches ascending). Leaves reduced to fused sheaths in whorls. Cauline sheaths 0.5–2.0 mm long; yellowish-green proximally and purplish-brown apically, and sometimes with hyaline margins; ending with 4–8 teeth. Cauline teeth lanceolate; apices acute. Rameal sheaths 0.3–0.8 mm long; attenuate; green and sometimes brown apically; ending with 3 or 4 teeth. Teeth triangular or lanceolate; apices acute. Sporiferous stems annual; erect; green or yellowish-green; simple. Strobilus 4.5 mm long, 2 mm wide.

Three Equisetum Linnaeus species are present on Ellesmere Island, although E. pratense Ehrhart has only been found once near Eureka ( GBIF 2020). Equisetum arvense and E. pratense both have vegetative stems bearing whorls of branches, whereas the vegetative stems are unbranched in E. variegatum ( Hauke 1993) . Equisetum arvense has ascending branches with attenuate, rameal sheath teeth, whereas E. pratense has spreading branches with deltate, rameal sheath teeth ( Hauke 1993).

Equisetum variegatum Schleicher ex F. Weber & D.

Mohr subsp. variegatum

Materials examined. CANADA – Nunavut • Ellesmere Island, CFS Alert ; 82°30′25″N, 062°36′45″W; 24 m a.s.l. ;

8 Aug. 2019; habitat: wetland on the margins of a small river, with peat and till as substrates, dominated by Alo- pecurus magellanicus and moss; QFA 0634993.

Identification. Plants 2–10 cm high; herbaceous; not caespitose. Fibrous roots and rhizomes present. Rhizomes black, purplish brown, or orange. Vegetative stems 2.5–9.0 cm long; evergreen; ascending or decumbent; green or yellowish-green; simple. Leaves reduced to fused sheaths in whorls. Cauline sheaths 1–3 mm long; green or yellowish-green proximally, with an apical broad black band, and white margins; ending with 4–8 teeth. Teeth triangular or lanceolate; apices acute or awned. Sporiferous stems not seen at Alert.

Characteristics allowing to distinguish E. variegatum from the other Equisetum species present on Ellesmere Island can be found under E. arvense .

Juncacea – Rush family