EQUISETACE.E. (HOKSETAIL FAMILY.) 621 



SERIES II. 



CRYPTOGAMOUS OR FLOWERLESS PLANTS. 



VEGETABLES destitute of proper flowers, and producing, 

 in the place of seeds, minute homogenous bodies (spores) 

 containing no embryo. 



CLASS III. ACKOGENS, 1 



Plants with a distinct stem, growing from the apex only, 

 containing woody fibre and vessels. 



ORDER 163. EQUISETACE^E. (HORSETAIL FAMILY.) 



Comprises only the genus 



1. EQUISETUM, L. SCOURING RUSH. 



Fructification terminal, spiked or cone-like. Spore-cases (sporangia) 6-7, 



borne on the lower surface of the peltate scales, 1 -celled, opening on the inner 



.side. Spores loose, furnished at the base with 4 club-shaped elastic filaments 



(elaters). Stems leafless, grooved, hollow and jointed, bearing at the closed 



joints a toothed sheath. 



1. E. Isevigatum, Braun. Stems perennial, mostly simple, the obtuse 

 ridges smooth, or roughened with minute tubercles ; sheaths appressed, with 

 numerous bristle-like caducous black teeth. Stiff clay soil, North Carolina, 

 and northward. Stem l-J-4 high. 



2. E. robustum, Braun. Stem tall (2-4 high), stout, simple; the 

 ridges roughened by a single row of tubercles; sheaths short, appressed, 

 with a black girdle above the base, and about forty 3-keeled ovate-subulate 

 deciduous teeth. Banks of the Chattahoochee River, Georgia, and west- 

 ward. 



3. E. hiemale, L. Stems 2- 3 high, simple, 20 -30-f arrowed, the 

 ridges studded with silicious papillae ; sheaths short-cylindrical, girdled with 

 black, the membranaceous teeth deciduous. Wet banks, Georgia, and north- 

 ward. 



