1 052 EQUISET ACE AE 



sheath close; central cavity one-half of the diameter of the stem or more 

 Sheaths 7-8 mm. long; stem stout, sparmgly branched. 5. E. fluviatile. 

 biieatlis less than 5 mm. long; stem slender, much branched. (Autumnal 

 forms of) I ^ artense 



Teeth of the sheatlis deciduous; plant unbranched or nearly so. ' 



Stem perennial, evergreen (except sometimes m E. laevigalum) , mosky 'simme^^sp^^^^ 



apiculate, with a rigid tip; stomata in regular rows. bi"M>ie. spii^e 



Central cavity present; stem more than 6-angled. except sometimes in E. varieaalum. 

 Teeth of the sheaths deciduous; stem tall and stout, many-grooved 

 Stem tubercled, rough. 



Sheath close, usually with a black or dark rmg near the base, then gravish 



and with a narrow dark border at the base of the teeth. ' 



Stem 1-2 m. high, stout; sheaths as broad as long. 7. E. robustum. 

 Stem 0.3-1 m. high, slender; sheath longer than broad. 



Sh^ths more ampUate above, green, with or without a narrow^'border 

 but no ring below. g j^ intermedium 



Stem not tubercled. smooth; sheaths enlarged upwards, with or without a dark 

 margin, out rarely with a ring below. 10 E laeviaatum 



Teeth of the sheaths persistent, white-margmed ; stem low, slender,5-10-grooved. 



Central cavity wanthig; stem 6-angIed. It f L'SS* 



.•+u*i^' ^'o^^-.^^f hr^ Spore-bearing stems 1-2,5 dm. high, 3-5 mm. in diameter, 



2-4 cm. lone:, 5-10 



peduncled 



fu ^^- *^ic^» 10-14-furro\ved, branched; branches 3-4-angled, solid; teeth of 

 the sheaths lanceolate, acuminate. In the faU the sterile stems sometimes bear 

 small cones 4-10 mm. long, mostly with sterile spores (var. scrotinum). Wet 

 banks: Greenl.—S.C.-^Calif.— Alaska; Eurasia. Plain— Alp, 



K ,u\f' fy\Y,^ti<^"P L. Stems 1-4 5 dm. high, 8-14-riaged, 3-4 mm. thick; 

 Dotn the lertile and the sterile ones branched; central cavity constituting half 

 the diameter; sheaths brown, loose, the teeth more or less coherent; primary 

 branches 4^5-angled, the secondary ones 3-angled; cones peduncled, 1-3 cm 

 long, 5-8 mm. thick Wet shady places: Newf.—Va.— la.— B.C.— Alaska! 

 Eurasia. Submont.—MonL My-Je. 



3. E, pratense Ehrh. Stems 2-4 dm. high, 3-5 mm. thick, 8-20-rido:ed, 

 the tertUe ones at first nearly unbranched, some developing short spreading: 

 branches, the sterile ones with long branches; central cavity one-third the diam- 

 eter-sheaths green, loose; teeth lanceolate with dark middle; branches 3-ridged- 

 teeth of the sheaths deltoid; cones pedimcled, 1-2 cm. long, about 5 mm. thick' 

 Alluvial soil: N.S.—N.J.— Colo.— Alaska; Em-asia. Submont.Subalp Ap- 



My. 



4. E, palustre L. Stems 2-9 dm. high, 3-5 mm. thick, 5-10-angled; branches 

 long, ascending, hollow, 4-7-angled; sheaths widened upwards; teeth lance-subu- 

 late; cones 1.^2.5 cm. long, 5-6 mm. thick. Wet places: Newf. — Conn. — Wyo. 



-Wash. — Alaska; Eurasia. Submofit.^MofiL Je-Au. 



5. E. fluviatile L. Stems 3-15 dm. high, 4-8 mm. thick, 10-30-angled- 

 central cavity four-fifths of the diameter; branches spreading or upcurved long' 

 4-6-angled, hollow; sheaths appressed; teeth dark brown, distinct, narrow -'cones 

 short-peduncled, 1.5-2.5 cm. long, 5-7 mm. thick. E. limosum L. ShaUow 

 water: Ne^vf.—N.Y.— Wyo.— Wash.— B.C. Plain—MonL Je-Jl. 



6. E. kansanum .J. H. SchaflFner. Stems 3-5 dm, high, 15-30-rrrooved 

 hght green; sheaths long, dilated above, green, with a narrow black band at the 

 top, rarely with a faint one below; cones short-peduncled, ovate or ovate-oblone; 

 1.5-2.5 cm. long, 7-8 mm. thick. Clay banks: Mo.— Utah— Mont. Plain— 

 oubmonL 



7. E. robustum A. Br. Stems 1-3 m. high, 8-12 mm. thick, 16^S-angled 

 dark green; ridges rounded, rough, with 3 rows of tubercles; sheath tight, about 

 as broad as long; teeth mostly persistent, lance-hnear, sharply 3-angled, black 

 with white margms; spike sessile, 1.5-2.5 cm. long, 6-7 mm. thick, strongly 

 apiculate. N.Y.— Md.— La.— Tex.— CaUf.— B.C. Plain— SuhmonL Je-\u 



affine Engehn. 

 q; ridges rotmded 



16-40-an 



