HORSETAIL FAMILY 



4. Equisetum palustre L,. Marsh Horsetail. 

 (Fig. 80.) 



Equisetum /xi/ustrel,. Sp. PI. 1061. 1753. 



Stems annual, slender, all alike, lo'-iS' long, very 

 deeply 5-g-grooved, the grooves separated by narrow 

 roughish wing-like ridges, the central canal very 

 small ; sheaths rather loose, bearing about 8 subu- 

 late-lanceolate whitish-margined teeth ; branches sim- 

 ple, few in the whorls, 4-y-angled, always hollow, 

 barely sulcate, more abundant below than above, their 

 sheaths mostly 5-toothed ; spike rather long; stomata 

 abundant in the furrows. 



In \vet places, Nova Scotia to Alaska, south to Maim-, 

 western New York, Minnesota and Arizona. Also in 

 Europe. July-Aug. 



5. Equisetum littorale Kuehl. Shore Horsetail. (Fig. 81.) 



Equisetum littoral? Kuehl. Beitr I'flanx ROM. 

 Reichs, 4 : 91. 1845. 



Stems annual, very slender, all alike, W-\V 

 high, slightly roughened, o-io-grooved, the 

 ridges rounded, the central canal one-half to two- 

 thirds the diameter; sheaths sensibly dilated 

 above, the uppermost inversely campanulate. 

 their teeth herbaceous, membranous at the mar- 

 gins, narrow, lanceolate ; branches of two kinds. 

 simple, some4-angled and hollow, some j-an gird 

 and solid, the first joint shorter or a trifle longer 

 than the sheath of the stem ; spike short with 

 abortive spores, these commonly with no elatere. 



On sandy river and lake shor-v M.unc and On- 

 tario to New Jersey ami 1'ennsylvania. wr*t to Brit- 

 ish Columbia. Also in Kuropc. Supposed to be a 

 hybrid. Aug. -Sept. 



6. Equisetum fluviatile L,. Swamp Horsetail. ( Fig. 82. ) 



Equisetum fluviatile L. Sp. PI. 1062. 1753. 

 Equisetum limosum L. Sp. PI. 1062. 1753. 



Stems annual, all alike, 2-4 high, slightly 

 io-3o-furrowed, very smooth, usually producing 

 upright branches after the spores are formed, the 

 stomata scattered. Sheaths appressed with about 

 18 dark brown short acute rigid teeth, air cavities 

 wanting under the grooves, small under the 

 ridges ; central cavity very large ; branches hol- 

 low, slender, smaller but otherwise much like the 

 stems, short or elongated ; rootstocks hollow. 



In swamps and along the borders of ponds. Nova 

 Scotia to Alaska, south to Virginia, Nebraska and 

 Washington. Also in Europe and Asia. May-June. 



