Equisetaceae
Horsetail, or Scouring Rush family.
Equisetaceae, horsetail family.
Vegetative morphology. Plants perennial herbs; 2–30(–100) cm high (further south); with creeping freely branched, shiny black underground stems. Roots pallid-brown, or red-brown, or black. Ground-level or under-ground stems horizontal, or vertical and often branched; rhizomatous, or stoloniferous; elongate, or compact; 0.4–1(–2) mm wide. Scales present (reduced leaves); 3–4, or 5–12; 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 existing for a single season or less. Petioles absent. Leaf blade bases truncate (into a fused sheath). Blades 0.5–3 mm long; 0.05–3 mm wide. Blades appressed to the stem; leathery, or membranous; straight; lanceolate, or triangular; flat; veins parallel, or appearing single-veined, or with inconspicuous veins. Blades adaxial surface glabrous. Blades abaxial surface glabrous. Blade margins glabrous. Leaf apices acuminate, or acute.
Reproductive morphology. Plants with sporangia, or only vegetative (appearing so, because cones mature late winter and are often not present during the summer). 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 L. The three
species found in the eastern Canadian Arctic Archipelago belong to subg.
Hippochaete (J. Milde) Baker.
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.
Illustrations. • Equistaceaee: horsetails. Family and genus characterised by the presence of fertile cones bearing sporangia on the underside of the sporophylls. Note two small flies searching for spores.
Cite this publication as: ‘S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, L.J. Gillespie, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, A.K. Brysting and H. Solstad. 1999 onwards. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 29th April 2003. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993, 1995, 2000) should also be cited (see References).
