_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.
[Sidenote: =Equisetum arvense= L. _Field Horsetail._]
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.
[Sidenote: =Equisetum sylvaticum= L. _Wood Horsetail._]
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.
[Sidenote: =Equisetum fluviatile= L. _Swamp Horsetail._]
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.
[Sidenote: =Equisetum hyemale= L. _Common Scouring rush._]
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.
[Sidenote: =Equisetum variegatum= Schl. _Variegated Equisetum._]
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.
[Sidenote: =Equisetum scirpoides= Michx.]
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.