Equisetaceae
Horsetail, Scouring Rush family.
Equisetaceae, horsetail family (subg. Hippochaete (J. Milde) Baker).
Plants with creeping freely branched, shiny black underground stems; less than 15 cm high (cold habitats), or more than 15 cm high; 2–30(–100) cm high (further south). Roots pallid-brown, or red-brown, or black. Ground-level or under-ground stems horizontal; rhizomatous, or stoloniferous; elongate, or compact; 0.4–1(–2) mm wide. Scales present (reduced leaves); 3–4, or 5–12; 0.5–10 mm long; glabrous. Aerial stems erect, or prostrate; conspicuously jointed with nodes covered by whorls of tiny leaves fused for part of their length into sheaths that are tipped with teeth; filiform, or not filiform; circular or oval in cross-section, or squarish; with 3–8(–12) ridges; glabrous. Leaves distributed along the stems; whorled; simple; evergreen, or deciduous. Petioles absent. Leaf bases truncate (into a fused sheath). Blades 0.5–3 mm long; 0.05–3 mm wide; appressed to the stem; leathery, or membranous; straight; lanceolate, or triangular; flat; with parallel veins, or appearing single-veined, or with inconspicuous veins; adaxial surface glabrous. Blades abaxial surface glabrous. Leaf apices acuminate, or acute. Plants asexual (appearing so, because cones mature late winter and are often not present during the summer), or reproducing by spores borne in sporangia. Sporangia in terminal cone-like structures.
Notes. Named from the latin equis, horse and seta, bristle referring to the coarse black roots of E. fluviatile.
Stems (and branches if any) jointed, fluted, hollow, often rough from silica deposited in cells; leaves borne in whorls at each node, fused at the base to form a sheath, but with free tips. The sporangia are grouped in terminal strobili (cones) with polygonal segments.
Cite this publication as: S.G. Aiken, M.C. LeBlanc, and M.J. Dallwitz 2000 onwards. Pteridophytes of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval.’ Version: 23rd February 2001. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000) , and Aiken, Dallwitz et al. (1999) should also be cited (see References).