28 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Order 3. EQUISETALES. 
4, EQUISETACEAE. Horsetail Family. 
1. EQUISETUM L. Horserat. 
Plant body rushlike, with jointed, mostly hollow stems; leaves reduced to a whorl 
of scales forming a sheath at the nodes; sporangia forming a terminal cone composed 
of peltate scales bearing several sporangia; spores all alike, supplied with coiled elaters 
attached at the middle and coiled spirally about the spore; prothallia terrestrial, 
green, usually dicecious, 
The family includes the plants which go under the name of “scouring rushes’”’ or 
“‘horsetails,’”’ which, while very numerous in past ages of the world, are now reduced 
to a single genus. 
KEY TO THE SPECIES. 
Annual; plant of two forms, one spore-bearing the other vege- 
tative; vegetative form much branched, with slender 4-angled 
branches; spore-bearing form not branched, brown......... 1, E. arvense. 
Perennial, not dimorphous, if branched at all the branches similar 
to the main stems, 
Stems nearly smooth, the tubercles inconspicuous; sheaths 
spreading upward; teeth deciduous, leaving a ring of 
triangular black tips..............2.-..5.-2-22-2-220-0- 2. E. laevigatum. 
Stems rough, the tubercles conspicuous; sheaths usually little 
or not at all spreading upward; teeth mostly adherent . 
to the bases. 
Stems generally less than 70 cm, high, frequently branched 
from the base........-......--- 220202 eee ee eee eee 3. FE. hiemale, 
Stems generally taller, 1 meter high or more, very hard and 
rough, usually little or not at all branched......... 4, EF. robustum, 
1. Equisetum arvense L. Sp. Pl. 1061. 1753. 
Type Locatity: ‘Habitat in Europe agris, pratis,’’ 
Range: British America to Virginia, New Mexico, and California, 
New Mexico: Taos; Rio Pueblo; Mogollon Mountains. Mountains, in the Transi- 
tion Zone. 
This is the common horsetail of the mountains, growing in very wet soil beside 
running water, It is usually associated with grasses, rushes, and sedges which cover 
the swampy meadows at elevations of 1,800 meters and more. Such meadows or 
marshy places usually go under the name of “ciénaga” (frequently corrupted to 
“siniky’’) or the diminutive “‘cienaguilla,’”’? The horsetail may be readily recognized 
in the vegetative state by its cluster of 4-angled jointed stems about 2 mm. in diameter, 
of a bright green color, that bear no proper leaves, The spore-bearing stalks are brown, 
6 to 8 mm. in diameter, 10 to 20 cm, high, and bear their cones singly at the top. They 
appear early in the spring, shed their spores, and soon die. 
2. Equisetum laevigatum A. Br. Amer. Journ. Sci. 46: 87, 1844, 
. SMOOTH SCOURING RUSH, 
Type Locauity: ‘On poor clayey soil, with Andropogon and other coarse grasses, 
at the banks of the river below St. Louis.”’ 
Rance: New Jersey and Louisiana to British Columbia, California, and Texas, 
New Mexico: Shiprock; Chama; Taos; Santa Fe and Las Vegas mountains; 
Ramah; Albuquerque; Mogollon Mountains; Mesilla Valley; Ruidoso Creek. In 
wet ground, in the Transition Zone, or lower, along streams, 
This is the chief scouring rush of the mountains, its smooth, hollow, jointed stems 
being common along most of the mountain streams and in the cienagas, There is but 
