814 OSDBE 169.— EQUISETACE^. 



§, Species fruitiog in spring and decaying before tiie following winter, (a) 



a Fertile ttems never branching, the sterile with simple, whorled branches.. ..Noa. 1, 3 

 a Fertile stems at length, like the sterile, with compound, whorled branches No. 3 



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



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



b Stems mostly simple, large, 20 to 40-furrowed Nos. 5, 6, 7 



b Stems always simple, very slender, 3 to 9-furro\ved Nob. 8, 9 



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

 furrowed, with simple, ascending, quadrangular braiiohes, and decumbent at base. 

 — Low grounds, Can. to Va. and Ky. Fertile stems first appearing, 6 — 8' higli, 

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

 teeth. Spike oblong, ^ — 2' long- Sterile stems rather taller than the fertile, 

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

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

 sheathed. April. 



2 E. ebtirneum Scbreb. Ivoey Horsetail. Fertile, st. simple, its sheaths 

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

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

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



3 E. sylvaticum L. "Wood Horsetail. Sterile and fertile sts. 12 or 13-fur- 

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

 low gi'ounds, N. States and Brit. Am. Stems 9 — 16' high; the fertile with 4 — 5 

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

 into several large, tawny red teeth or segments; the sterile taller and more slen- 

 der, with more numerous whorls of branches. The branches are all subdivided 

 and curved downwards. Spilce oval-oyhndrie, pedicellate. May. 



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

 branches from the middle joints, simple, short, 5-sided, smooth ; spike oblong- 

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

 3f high, slender, rarely simple, generally with 2 — 6 whorls of branches about th» 

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

 white at the summit, tipped with as many black, subulate teeth as there are fur- 

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



5 E. Isevigatum Braun. Tall, erect, simple or somewhat branched; sheaths 

 elongated, appressed, green, with a Hack border, of about 22 Ivs., sheaths of tho 

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

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



6 E. robtistum Braun. Very tall and stout, simple or somewhat branched 

 above ; sheaths short, appressed, with a black girdle .above the base, rarely with a 

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

 deciduous, leaving an exact truncate margin. — Banks of tlie Western rivers, Terro 

 Haute, to St. Louis and South. Forms with fewer Ivs. in the sheaths seem to 

 connect this with the next. 



7 B. hyemale L. Sogurikg Eush. Sts. all simple, erect, very rough, each 

 bearing a terminal, ovoid spike ; sheath cinerous white, black at the base and sum- 

 mit, short, with about 20 subulate, awned and deciduous teeth. — "V"ery noticeable 

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

 united at base from the same root. Sheaths 2^3" long, 1 — 2 j' apart, the white 

 ring much broader than the black, at length entire from the falling off of the teetk 

 The roughness of the cuticle is ov/ing to the sUex in its composition. June. 



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

 straight and very tlender, roughish, 5 to S-furrowed; sheaths very short, brown, 

 teeth 5 to 9 ovate with broad, scarious 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 B. Bcorpoidea Mx. Stems growing in tufts, thread-like, 4 to 8', flexuous and 

 recwrved, 3 or i-furrowed ; sheaths black, 3 or 4-toothed, teeth short-ovate, sca- 

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



