E. boreale Bong., Mem. Acad. Sci. Petersb. Ser. 6, 2: 174.1832.
E. saxicola Suksdorf, Deutsche Bot. Monats. 19: 93.1901.
E. calderi Boivin, Amer. Fern J. 50: 107. 1960.
Stems heterophyadic, the vegetative 2-100 cm tall (~
32) with internodes 1.4-4.5 cm long (m 3.0) and 0.8 to 4.5 mm
in diameter (m 1.9), having 4-14 (m 8) ridges. Internally, both
carinal and vallecular collenchyma present, and chlorenchyma present
under the ridges but interrupted under the valleys, the central
canal 1/3-2/3 diameter of stem. Endodermis outer common. Sheats
nearly square, 1-10 mm long (m 4.6), 1-9 mm wide (m 3.4) with
short (1-3.5 mm long, m 2.2) narrow, dark teeth, often cohering
in pairs. Sheath segments often with slight central groove. 435
Branches in regular whorls, ascending, the first branch internode
longer than the subtending stem sheath, 4-14 (m 9.5) mm long.
Ridges 3-4 (m 3.4), the silica profile of blocky sawteeth. Branch
teeth narrow, long-pointed, the tips often reflexed. Commissure
long but lacking anchorcells, not furrowed. Valleys channeled,
with stomata in bands of 2-3 stomata wide on each side. Silica
pilules scattered over surface of stomate, strongly outlining
it and lining the stoma. Mamillae small, in longitudinal rows.
Branches solid. Coniferous stems unbranched, brown, succulent,
shorter than the vegetative but with larger sheaths. Precocious
and ephemeral, occasionally persisting and becoming branched and
green. Occasionally cones borne on vegetative stems.
Cones 17-40 (m 24.8) mm long, on peduncles 22-55 (m 37.5) mm long.
Rhizome dark brown to black, dull, covered with hairs,
occasionally bearing tubers.
Spores 33-48 µm in diameter (m 42).
Gametophytes Plate tips rounded to funnel-shaped, sparse
or absent on males. Antheridia protuberant, 2-3 times longer than
wide, with 2-4 (mostly 4) cap cells.
LINN, Packet 1241 sheet 4 (designated by Hauke, 1966. Sheet 3,
pinned to it and labeled "E. arvense" by Linnaeus,
is E. sylvaticum).
Coning February (southerly locales) to July (far north). Mostly
in April and May.
Throughout Canada and the USA except the southeast (Florida, Georgia,
Alabama, Louisiana, Mississippi, Tennessee). Throughout Europe
and Asia south to Turkey, Iran, the Himalayas, and across China
(except the southeastern part) Korea and Japan.
Marshes, swamps, ditches, river banks, open fields, open woods,
and fill areas, such as road sides, and railroad embankments.
This species has been separately discussed in Hauke, 1966.
HAUKE, R.L. (1978)
A taxonomic monograph of the genus Equisetum subgenus Equisetum.
Nova Hedwigia 30, p385.
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