40 



EOUISETACEAE 



3. Equisetum palustre L. 



j\Iarsh Horsetail. Fig. 83. 



Eqtiiscttim palustre L. Sp. PI. 1061. 1753. 



Rhizome angled, shining, without felt or tubers. 

 Aerial stems conform, annual, slender, erect, 25-90 cm. 

 long, deeply 5-10-angled (the central canal very small), 

 usually naked and nearly smooth below, freely branched 

 and rough above, the ridges sharply elevated but 

 roimded ; sheaths rather loose, widened upward, mostly 

 green, the constituent leaflets keeled toward the base 

 and with a distinct carinal groove extending into the 

 teeth, these usually black, lance-subulate, with broad 

 white hyaline margins ; branches coarse, in scant 

 verticils, simple, hollow, 4-7-angled, rough with cross- 

 l)ands of silica, the sheaths similar to those of the stem; 

 spikes short-pedunculate, 1-2.5 cm. long, terminating 

 some of the stems, smaller ones sometimes terminating 

 the branches. 



Wet, shady places, Boreal Region; Alaska to Newfoundland, 

 south to Oregon, Illinois, and New Jersey; Europe. Type lo- 

 cality, European. 



4. Equisetum fluviatile L. 



Swamp Horsetail. Fig. 84. 



llquisctum fluviatile L. Sp. PL 1062. 1753. 

 Equisetum limosnm L. Sp. PI. 1062. 1753. 



Rhizome shining, rarely tuber-bearing, with a broad 

 central cavity. Aerial stems conform, erect, 60-150 

 cm. long, 4-6 mm. thick below, smooth, with 10-30 

 shallow grooves (the central' cavity very broad), verti- 

 cillate branches developed in the upper half or two- 

 thirds, sometimes wanting; sheaths nearly as broad as 

 long, appressed, concolorous ; teeth narrowly lanceolate, 

 acute, rigid, erect, distinct, dark, with narrow hyaline 

 margins; lower internodes up to 5 cm. long, yellowish 

 green or flesh-colored, shining, often developing a few 

 6-8-angled secondary stems, these equaling the mam 

 one ; verticillate branches 2-15 cm. long, 4- or 5-angled, 

 arcuate-ascending, with rough low-winged angles ; 

 sheaths rigid, with sharp, erect or spreading, green or 

 black-tipped teeth ; spikes short-pedunculate, cylindric. 

 1-2 cm. long, terminating the main and secondary 

 stems. 



Swamps and in shallow water at the border of ponds and streams, Hudsonian to Transition Zones; 

 Alaska to Labrador, south to Oregon, Wyorning, Nebraska, and Virginia; Eurasia. Type locality, European. 



5. Equisetum fiinstoni A. A. Eaton. 

 California Horsetail. Fig. 85. 



Equisetum funstoni A. A. Eaton, Fern Bull. 11: 10. 1903. 



Aerial stems up to 75 cm. long, naked, or with 

 elongate, scattering or regular verticillate branches 

 in the upper part, a spreading tuft of numerous 

 branched sterile shoots borne at the base (the 

 winter form) ; main stems annual, erect, 20-30- 

 angled, very rough, the ridges with many .sharply 

 projecting transverse bands of silica; central 

 cavity very broad ; sheaths elongate, funnel-form, 

 green (rarely with a dark basal ring), the bases 

 of the elongate coherent teeth small, persistent, 

 horny, strongly incurved with age, forming a very 

 narrow blackish band; uppermost sheaths campan- 

 ulate, the spike (1-2 cm. long) exserted or not, 

 obtuse or acute. 



Damp places, in partial shade, Sonoran Zones; southern 

 California, from Santa Barbara County southeastward; also 

 in the Panamint Mountains, Inyo County, the type locality. 



