482 EQUISETACE^. Eqcisetum. 



**♦ stems timple, or irregularly branched from the root. 



4. Equisetum hyemale, Linn. Scouring Rush. Shatie- grass. 

 Stems numerous, simple, naked, erect, very rough ; sheallis short, blackish at the base and 



top, with about 14-20 very small finally deciduous teeih. — Linn. sp. 2. p. 1062; Engl, 

 hot. «. 915 ; Pursh, fl. 2. p. 652 ; Bigel. fl. Bost. p. 382 ; Torr. compend. p. 359 ; Beck, 

 hot. p. 446 ; Darlingt. fi. Cest. p. 574 ; Braun ^- Engl. I. c. p. 89. 



Stems 15 inches - 3 feet high, persistent through the winter, terete, from one-fourth to one- 

 third of an inch in diameter ; the ridges roughened with minute concretions of silica, of n pale 

 somewhat glaucous green. Stomata disposed in 2 distinct ranges. Sheaths 3-4 lines long, 

 with a broadish dark colored band at the base, and usually a narrower one at the upper margin ; 

 when young, furnished with minute blackish awned teeth, which fall off early, leaving the 

 sheath truncate, and crenulate or entire. Spike ovate, with black scales. 



Swamps and wet banks : frequent. Fl. May - June. The epidermis of this species abounds 

 more in silex than any of the others, so that the stems are often employed for scouring wood 

 and metals. 



5. Equisetum variegatum, Schleich. Variegated Rough Horsetail. 

 Stems several, usually decumbent or assurgent, simple or only branching at the base, with 



4-8 striae ; rough sheaths with membranaceous lanceolate teeth, blackish at the base. — 

 Engl. hot. t. 1987 ; Hook. Jl. Bor. Am, 2. ji. 270 ; Oakes, cat. pl. Vermont, p. 35 ; Braun 

 ^ Engl. I. c. p. 90. 



Stems 6-12 inches long; the little ridges furnished with two rows of siliceous tubercles, 

 which are separated by a furrow, with a single row of stomata on each side. Sheaths blackish ; 

 the teeih 4-carinate, persistent, lipped with slender deciduous awns. Heads resembling those 

 of E. hyemale, but smaller. 



Wet sandy places, among rocks, near Niagara Falls {Dr. Kinnicutl). Our plant agrees 

 well with European specimens of E. variegatum in my herbarium. 



6. Equisetum scirpoides, Michx. Smallest Rough Horsetail. 

 Stems cespilose, much branched from the root, ascending, naked, filiform, rough ; sheaths 



blackish, with few awned teeth. — Michx. Jl. 2. p. 281 ; Pursh, fl. 2. p. 652 ; Bigel. fl. 

 Bost. p. 3S4 ; Braun <^ Engl. I. c. p. 91. E. variegatum, Torr. compend. p. 390; Beck, 

 hot. p. 446, not of Schleich. E. variegatum, var. minus, Hook. fl. Bor.-Am. 2. p. 270. 



Stems growing in dense tufts, 4-8 inches long, very slender, persistent through the winter, 

 often curved or flexuous, 5 - 6-angled, much roughened with siliceous concretions. Stomata 

 in single rows. Sheaths minute, blackish, with 3-6 subulate whitish awned teeth, the 

 awns of which are more or less deciduous. Spikes ovate-capitate, 2-3 lines long, of a 

 blackish color. 



Rocky shady places, on springy hill-sides ; northern and western counties. This species, 

 which is the smallest of the genus, grows also in the north of Europe. Hooker considers it 

 a small variety of E. variegatum, but I have never seen any intermediate forms. 



