412 CLASS XXIV. ORDER I. 



Equisetum arvense. L. Field Horsetail. 



Fertile scape naked ; barren frond with whorled 

 branches, decumbent. L. 



The fruitful stems of this plant appear in April, and soon de- 

 cay. They are erect, smooth, furrowed, and without branches, 

 their joints surrounded with large, swelling sheaths, which end 

 in long, blackish teeth. Spike terminal, oblong-ovate, with a 

 membranous border below it. The barren stems are taller and 

 more durable ; they are erect, or ascending at base, roughish, 

 their joints furnished with sheaths and large whorls of simple 

 ascending branches. These branches are three or four cornered, 

 with sheaths at their joints, ending in the same number of teeth. 

 — Moist ground, South Boston. — Perennial. 



Equisetum sylvaticum. L. Wood Horsetail. 



Branches compound, carving downward, rough. 



The fertile stems are erect, round, furrowed, jointed. Joints 

 invested with large, loose sheaths, which divide into a number 

 of broad teeth at top. Branches very slender, in a whorl pro- 

 ceeding from the upper joint, immediately below the sheath, 

 divaricated and curving downward. The second joint from the 

 top is furnished with a whorl of shorter branches, and sometimes 

 also the third. Ament ovate, terminal, composed like the rest, 

 of peltate, hexagonal scales. The barren stems are smaller and 

 higher, their joints all furnished with whorls of branches, which 

 are much longer, and considerably subdivided. — Low grounds, 

 Roxbury, Cambridge. — Perennial. 



Equisetum scirpoides. Mx. Small Horsetail. 



Stems simple, ascending, smooth, filiform, with 

 spikes at top; sheaths three toothed, blackisli, teeth 

 awned, the tips caducous. 



A very small species, not larger than the leaves of the fore- 

 going. Stems simple, crowded, three or four inches high. — la 

 Plainfield. Dr. Porter. 



