Equisetum. Equisetum hyemale L. Horsetail. Scouring Rush. Prele, Fr. Schachtelhalm, G. (Fam. Equisetaceae.)—An indigenous plant, with slender annual stems from 3 to 9 dm. high, growing abundantly throughout the United States, and preferring wet places, as the banks of streams, etc. The plant derives its name of scouring rush from its use in scouring, for which it is fitted by the silicious character of the stems. Examined by F. J. Young (A. J. P., 1886, 419), it yielded to petroleum benzin as a solvent 1.4 per cent. of a brownish-green, semi-liquid, fixed oil, which was readily saponified. It also contained a green semi-solid resin, sugar, and mucilage. The infusion of the whole plant is used sometimes in dropsical and renal diseases, but Cow (A. E. P. P., 1912, lxx, p. 393) has shown that the diuretic action of equisetum is very feeble.