CLASS XXIV. ORDER I. 411 



opening outwards, the other marginal and opening 

 inwards. 



CRYPTOGAMIA. 



FILICES. 



420. EQUISETUM. 

 Equisetum hyemale. Z/. Rough Horsetail. ScouringRush. 

 Stem naked, very rough, mostly branched at base; 

 sheaths whitish, black at the base and summit. 



Found in moist woods at Lynn and elsewhere. Stems erect, 

 without branches, except at base, hollow, naked, furrowed, the 

 ridges rough with minute teelh, which are hardly visible without 

 a glass. The joints of the stem are surrounded with short 

 sheaths, colored with black and white rings, and toothed at the 

 top. The fruit grows in an ovate, terminal ament, composed of 

 peltate, six sided scales, bearing the seeds inside. 



The whole surface of the stem is rough, like a file, and is 

 used in scouring and polishing metallic vessels. Its cuticle, ac- 

 cording to Sir H. Davy, contains a considerable portion of sili- 

 ceous earth. — Perennial. 



Equisetum uliginosum. Muhl. Pipes. 



Stems somewhat branched ; branches from the 

 middle joints, unequal. 



A very tall, slender species, growing in the water at the edges 

 of rivers and ponds. Stems erect, round, furrowed, nearly 

 smooth. Joints invested with smooth sheaths ending in even, 

 acute, black teeth. Both the barren and fertile stems are fur- 

 nished with a few short branches, chiefly from about the middle 

 joints. The lowermost and uppermost of these are generally 

 single or in pairs, the rest in unequal whorls. Ament terminal, 

 oblong-ovate. — Banks of rivers, &c. — Perennial. 



Under the name of pipes, this plant is prized by farmers as a 

 valuable food for cattle, who are extremely fond of it. 



