3(2). Sheaths dilated upward, green (when young), with a narrow black band at 

 the summit below the promptly deciduous teeth, frequently with a 

 second irregular band below; stems smoothish, only slightly 

 scabrous 3. E. laevigatum. 



3. Sheaths cylindric, tightly pressed to the stem, ashy-gray, usually with 2 black 

 bands, sometimes entirely black, the teeth mostly subpersistent or 



irregularly deciduous; stems firm, scabrous 



4. E. hyemale var. affine. 



1. Equisetum arvense L. Bottle brush. Fig. 8. 



Rhizome extensively creeping and branching, dark-felted and tuberiferous; 

 aerial stems dimorphic, with scattered stomata; fertile stems appearing in early 

 spring, erect, usually thick and succulent, light-brown to yellowish-white, simple, 

 to about 3 dm. tall, soon withering, provided with conspicuous lax scarious some- 

 what dilated nodal sheaths that have 8 to 12 brown lance-acuminate teeth; cones 

 cylindric to ovoid, obtuse, to 4 cm. long and 1 cm. diameter; sterile stems appear- 

 ing as the feitile stems wither, erect to ascending, slender, green, 8- to 14-furrowed, 

 with whorls of branches at the upper nodes, to about 7.5 dm. tall, usually smaller, 

 the nodal sheaths tipped with about 12 sharp brown teeth; branches numerous in 

 dense verticils, spreading to ascending, solid, mostly simple and 2.5 dm. long or 

 less, about 1 mm. thick, 3- or 5-angled, provided with sheaths that have erect 

 triangular-lanceolate sharp teeth. 



In sandy or clayey soil along streams and about lakes, in meadows, low ground 

 and open woodlands, and on railroad embankments, in Tex. found only at Buffalo 

 Spring (now known as Buffalo Lakes) in Lubbock Co., in the Plains Country, 

 rather widespread and frequent in the mts. of N.M. (Colfax, Catron, Sandoval, 

 Mora, San Miguel, Taos and Rio Arriba cos.) and Ariz. (Apache, Navajo, 

 Coconino, Graham and Gila cos.); from Nfld. w. to Alas, and s. to N.C., Ala., 

 Tex., N.M., Ariz, and Calif.; also Euras. and N.Afr. 



Forma ramulosum (Rupr.) Klinge has been found in Arizona (Gila Co.). Its 

 branchlets are again branched. 



2. Equisetum kansanum J. H. Schaffn. Summer scouring-rush. Fig. 6. 



Stems 3-10 dm. tall, 2-7 mm. in diameter, usually very smooth to the touch, 

 light-green; sheaths elongate, dilated upward, pale-green except for a narrow 

 black band at summit, the articulate teeth soon deciduous; cone sessile or shortly 

 pedunculate, 1-2.5 cm. long, 5-8 mm. in diameter. 



In moist or dry sandy or clayey soil, on bluffs, along irrigation ditches and 

 lakeshores, in prairies, ditches, sloughs and among grasses and shrubs in marsh 

 and swamp areas, in Tex. mostly in the Plains Country, Trans-Pecos and s.e. 

 Edwards Plateau, with a lone station in Somervell Co. in the Blackland Prairies; 

 from Mich, to B.C., s.w. through the Lake States to Mo., Tex., N.M. and s. 

 Calif.; also n. Mex. 



Except for the absence of the hard blackish apicule on its cone, the smoother 

 texture of its cone, and its annual habit, this species approaches very closely 

 E. laevigatum. Its obvious relationship to that species has resulted in its being 

 recently relegated to it as subsp. Funstonii (A. A. Eat.) Hartman. 



Two rather insignificant growth forms of this species occur in our area; f. 

 caespitosum (A. A. Eat.) Broun, with many small rough stems clustered around 

 a large central one, and f. variegatoides (A. A. Eat.) Broun, with 6 to many small 

 prostrate to ascending stems arising from the apex of the rhizome or about the 

 old stems of the previous year. 



3. Equisetum laevigatum A. Br. Cola de caballo, canuela, smooth scouring- 



rush. Fig. 6. 



Rhizome creeping and ascending, dark-brown to blackish, naked, with felted 

 46 



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