** Branchless perennial species. 
§ Ridges of the stem with one line of tubercles. 
2. E. praealtum Rafin. PI. 8. 
Equisetuin prealtujn Rafin. 1817. Fl. Lud, 13. 
E. robustum X. Br. 1843. Amer. Journ. Sc. 46: 
88, (transl. by Dr. Engelmann) . Eaton^m Gray, 
1. c. 677. Underzu, in 111. Fl. i : 38 ; Nat. Ferns 
129; in Britt. 1. c. 23. Clute^ 1. c. 26. 
Giant Scouring Rush. 
Plants 2 m. or higher ; stems i cm. or wider at the 
base and iisua-ly simple; sheaths short, appressed mark- 
ed with two black girdles ; teeth caducous ; spikes ovate, 
I cm. or longer, mucronate. 
Along riverbanks and creeks. Summer, 
Observed in various places along the Potomac River and its 
tributaries, from Glen Echo, Md., to Chapel Point. 
§§ Ridges of the stem with two obscure lines of 
tubercles, 
3. E. hyemale L. PI. 8. • 
Eguisetum scapo nudo simplicissimo <& Gron. FI, 
Virg. T96, 
m 
