Equisetaceæ
Horsetail Family
Green, rush-like plants with usually hollow, jointed, simple or often much branched stems, rising from subterranean rootstocks; the branches verticillate.
Leaves reduced to toothed sheaths; sporanges clustered beneath the scales of terminal, cone-like spikes.
Stems annual, the fertile appearing in early spring before the sterile; fertile stems 4—10 inches high, soon withering, light brown, their loose sheaths mostly distant, whitish, ending in about 12 brown acuminate teeth; sterile stems green, much branched and slender, 2 inches to 2 feet high with numerous, mostly simple, 4-angled solid branches with 4-toothed sheaths.
In moist sandy soil throughout the region, frequent in wet woods and swampy places.
Stems annual, the fertile appearing in early spring before the sterile, at first simple, at length much branched, resembling the sterile except in the withered apex; stems 8—20 inches high, producing verticillate compound branches which are curved downward; sheaths loose and cylindric, those of the stem whitish, with 8—14 rather blunt brown teeth.
In moist sandy woods and thickets in the Selkirks, not common.
Stems annual, all alike, 2—4 feet high, bluish-green, smooth, usually producing upright branches after the spores are formed; sheaths appressed with about 18 dark brown or nearly black, short acute teeth.
In sloughs and shallow ponds throughout the region, frequent.
Stems stiff, evergreen, 2—4 feet high, rough, 8—34-furrowed, the ridges with two distinct lines of tubercles; sheaths rather long, cylindric, marked with one or two black girdles, teeth dark brown or nearly black and membranous, soon deciduous; spikes tipped with a rigid point.
In wet places and on banks and slides in the valley of the Kicking Horse River.
Stems perennial, slender, evergreen, 6—18 inches long, rough, usually simple from a branched base, commonly tufted, 5—10 furrowed; sheaths companulate, distinctly 4-keeled, green variegated with black above; the teeth 5—10, each tipped with a deciduous bristle.
In moist, sandy soil throughout the region up to an elevation of 7000 feet, sometimes forming large patches.
Stems perennial, evergreen, very slender, 3—6 inches long, rough, flexuous and curving, growing in tufts closely matted to the ground, mostly 6-furrowed with acute ridges, simple or branching from near the base; sheaths black, with three membranous rather persistent bristle-tipped teeth.
On moist sandy shaded banks throughout the Rockies.