314 Ordee 159.— EQUISETACKdS. 



$ Species fruiting in spring: and decaying before the following winter, (a) 



a Fertile stems never branching, the sterilo with simple, whorled branches.. ..Nos. 1, • 

 a Fertile stems at length, like the sterile, with compound, whorled branches No. 8 



§ Species fruiting in summer and lasting through the following winter. 



b Stems with whorls of simple branches from the middle joints No. 4 



b Stems mostly simple, large, 20 to 40-furrowed Nos. 0, 6, T 



b Stems always simple, very slender, 3 to 9-furrowed Nos. 8, 9 



1 E. arvense L. Field Horsetail. Fertile sts. erect, simplo; sterile, 12 to 14- 

 furrowed, with simplo, ascending, quadrangular branches, and decumbent at base. 

 — Low grounds, Can. to Va. and Ky. Fertile stems first appearing, G — 8' high, 

 with 3 — 5 joints surmounted by large, inflated sheaths cut into long, dark brown 

 teeth. Spike oblong, 4 — 2' long. Sterilo stems rather taller than the fertile, 

 remaining through the season, after theso have decayed. At each joint is a whorl 

 of simple, rough branches, issuing from the baso of the sheaths, their joints also 

 sheathed. April. 



2 E. eburneum Schreb. Ivory Horsetail. Fertile, st. simple, its sheaths 

 numerous, of 3 lvs. with subulate teeth ; sterile st. very smooth, ivory-white, about 

 30-/ arrowed ; branches simple, sheaths 4 or 5-leaved, with erect, subulate teeth.— 

 Shores of tho Great Lakes. Barren stems 2 to 5f high. May. 



3 E. sylvaticum L. "Wood Horsetail. Sterilo and fertile sts. 12 or 13-fvir- 

 rowed, with compound, rough, deflexed, angular branches. — Grows in woods and 

 low grounds, N. States and Brit. Am. Stems 9 — 1G' high; the fertile with 4 — 5 

 whorls of branches from tho base of tho sheaths which aro 2 — 3' apart, and cleft 

 into several large, tawny red teeth or segments; tho sterilo taller and more slen- 

 der, with more numerous whorls of branches. Tho branches aro all subdivided 

 aod curved downwards. Spiko oval-cylindric, pedicellate. May. 



4 E. limosum L. Pipes. Sts. somewhat branched, erect, striate-sulcatc ; 

 branches from tho middle joints, simple, short, 5-sided, smooth ; spiko oblong- 

 ovoid ; sheaths appressed. — Borders of ponds and swamps, frequent. Stems 2 — « 

 3f high, slender, rarely simple, generally with 2 — G whorls of branches about th» 

 middle. Branches very irregular in length and position. Sheaths 3 — 4" long, 

 white at tho summit, tipped with as many black, subdlato teeth as there aro fur- 

 rows (15 — 20). This species is greedily devoured by cattle. July. 



5 E. laevigatum Braun. Tall, erect, simplo or somewhat branched ; sheatlts 

 elongated, appressed, green, with a black border, of about 22 lvs., sheaths of tho 

 branches about 8-leaved, with subulate, persistent points. — Dry soils, Wis. and 

 South, along tho Miss. River. Stems 18' to 2 or 3f. Apparently distinct. 



6 E. robustum. Braun. Very tall and stout, simplo or somewhat branched 

 above ; sheailis sliorl, appressed, with a black girdle above tho base, rarely with a 

 black border, consisting o/40 (in tho branches 11) leaves, tho ovate-subulate points 

 deciduous, leaving an exact truncate margin. — Banks of the Western rivers, Terre 

 Haute, to St. Louis and South. Forms with fewer lvs. in tho sheaths seem to 

 connect this with tho next. 



7 E. hyemale L. Scouring Rush. Sts. all simple, erect, very rough, each 

 bearing a terminal, ovoid spiko ; shtath cinerous white, black at the base and sum- 

 mit, short, with about 20 subulate, awned and deciduous teeth. — Very noticeable 

 in wet, shady grounds, and by brooksides. Stems about 2f high, often 2 or more 

 united at baso from the same root. Sheaths 2 — 3" long, 1 — 2\' apart, the white 

 ring much broader than the black, at length entire from the falling off of tho teeth. 

 The roughness of tho cuticle is owing to tho silex in its composition. June. 



8 E. variegatum Schleicher. St. branching only at base, G to 12', simple, 

 straight and very slender, roughish, 5 to 9-furrowed; sheaths very short, brown, 

 teeth 5 to 9 ovate with broad, Ecarious margins and tipped with deciduous seta- 

 ceous points. — Banks of streams, N. Eng. to Wise, and Can., not common. Inter- 

 nodes about 1'. July. 



9 E. scorpoides Mx. Stems growing in tufts, thread-like, 4 to 8', flexuous and 

 recurved, 3 or i-furrowed ; sheaths black, 3 or 4-tootbed, teeth short-ovate, eca- 

 rious, bristle- pointed. — Hilly woods, Penn. to N. Eng., Wise, and Can. July. 



