EaUISETACEiE. 455 



Moist grounds. Arct. Amer. to Virg. W. to the N. W. Coast. April, May. 

 %.. — Sterile xtcms 10 — 15 inches high, with whorls of ascending branches, which 

 are eitlier simple or somewhat divided. Fertile stems 6 — 8 inches high, with 

 brownish or purple sheaths. Spikes oblong, obtuse ; the scales at first approxi- 

 mated, at length more open. Fidd Horse-tail. 



** Fertile stems atlengthbranclied, bearing tlie fructification at the same time 

 vnth the branches. 



2. E. sylvaticum Linn. : sterile and fertile stems both branched, about 

 12 — furrowed; branches compound, curved downwards; sheaths loose, 

 deeply cleft into several broad-lanceolate membranous teeth. 



Moist grounds. Arct. Amer. to Virg. and Ohio. June, July. 1] . — Stems 12—18 

 inches high ; the sterile ones usually taller and more slender. Sheaths divided 

 into 8 — 17 teeth or leaves, whose points are connected in 2 — 4 or more lobes. 

 Spike oblong. Wood Horse-tail. 



3. E. palustre Linn. : stem deeply grooved, roughish, 7 — 8-angled ; 

 branches whorled, i^fople, gradually shorter upwards; sheaths distant, cut 

 at the apex into 6 — 10 fuscous teeth. 



Swamps. Arct. Amer. to Virg. June. 1\.. — Stems 12 — 18 inches high, gen- 

 erally with simple erect whorled branches. Sheaths mostly with 7 — 9 teeth. 

 Spike an inch long, slender and blackish. A variable species. 



Marsh Horse-tail. 



4. E. limosum Linn. : stem smooth, with 16 — 21 striae, sometimes simple; 

 branches nearly erect, simple, short; teeth of the sheaths short, rigid, dis- 

 tinct. 



Borders of swamps and ponds. Can. to Virg. W. to Wise. June, July. %■> 

 SteTiis 2 — 3 feet high, erect, simple, or with -a few whorls of branches at the top. 

 Sheaths numerous, appressed, usually with 17 — 20 brownish or blackish teeth. 

 Spike oblong, scarcely an inch in length. Easily distinguished from the preceding 

 Dy the structure of its stem and by its teeth. Smooth Swamp Horse-tail. 



*** Stems simple or branched only at base.. 



5. E. hyemale Linn. : stems numerous, simple, naked, erect, very rough ; 

 sheaths short, blackish at the base and apex, with about 14 — 20 very small 

 obtuse finally deciduous teeth. 



Wet woods and marshes. Can. to Penn. W. to Miss, and Ken. June, July. 

 %. — Stems 1 — 2 feet high, naked, furrowed, pale and somewhat glaucous green. 

 Sheaths 2 — 4 lines long, the teeth deciduous. Spike ovoid, blackish. The cuti- 

 cle abounds in silica, and the stems are well suited for the polishing of hard 

 woods and the metals, Scounng Rush. Shave-grass. 



6. E. variegatum Schleich. : sterns several, usually decumbent or assurgent. 

 simple or only branched at the base, rough, fiUform, with 4 — 8 striae; 

 sheaths with membranaceous lanceolate teeth, blackish at the base. 



Wet sandy places. Arct. Amer. to N. Y. July. %-. — Stems 6 — 12 inches 

 long, several from the same root. Sheaths blackish, consisting of about seven 

 4-keeled persistent teeth. Spike ovoid, blackish, smaller than in the preceding. 



Variegated Rough Horse-tail. 



7. E. scirpoides Mich. : stems cespitose, much branched from the root, 

 ascending, naked, filiform, rough ; sheaths blackish, with a few awned 

 teeth. E. variegatum Torr. Comp. E. variegatum var. minus Hook. 



Wet rocky places. Arct. Amer. to N. Y. and N. Eng. %. — Stems in dense 

 tufts, 4 — 8 inches long, very slender, 5 — 6-angled. SheatJis minute, blackish. 



