Bot. Pl. equisetums, -æ. [a. L. equisētum (more correctly equisætum), f. equus horse + sæta bristle.] A genus of plants called popularly Horsetail or Mare’s-tail; the typical genus of the N.O. Equisetaceæ.
1830. Lyell, Princ. Geol., I. 101. The fossil ferns, equiseta, and other plants of the coal strata.
1847. Darwin, in Life & Lett. (1897), I. 360. His oolitic upright Equisetums are dreadful for my submarine flora.
1873. Dawson, Earth & Man, vi. 129. Mares’ Tails or Equisetums.
