340 CRYPTOGAMIA— FILICES. Equisetum. 



E. nudum. Rail Syn. 131. Ger. Em. 1 113./. 

 E.junceum. Dalech. Hist. 1071. f. 

 E. foliis nudum, non ramosum. Baidi. Pi?!. 16. 

 Equisetum. Camer. Epit. 70. f, A. 

 Hippuris, Trag. Hist. 692./. 



/3. Equisetum foliis nudum;, ramosum. Bauh. Pin. 16. Rail Syn. 



132. 

 E. tertium. Matth. Valgr. v. 2.375./? Camer. Epit. 772./?. 



In boggy woods, but not very common. 



In Lancashire, Warwickshire, and Wiltshire. Ray, Merret. In 

 several parts of Yorkshire, Norfolk, and other counties, as well 

 as in Scotland. 



Perennial. July, August. 



Root black, variously branched. Stems erect, of a deep glaucous 

 green, from one to two feet high, cylindrical, uniformly and ra- 

 ther copiously furrowed, the furrows minutely toothed, and of a 

 stony hardness. Sheaths tight, rather short, whitish, with a 

 circle of black at the top and bottom, and crowned at first with 

 a row of black, lanceolate, pointed teeth, which very soon fall 

 off, as Willdenow has remarked. Catkin terminal, solitary, at 

 first ovate, pointed, and black j subsequently elliptical, abound- 

 ing with whitish powdery seeds. 



The stems are generally quite simple, or branched towards the bot- 

 tom only J nor have 1 ever seen them so much divided as in 

 Gerarde's figure, still less like the cuts indicated, on Bauhin's 

 authority, under the variety /3, to which therefore marks of doubt 

 are subjoined. 



That eminent chemist Sir Humphry Davy first detected a quan- 

 tity of pure silex, or flinty earth, in the furrowed cuticle of this 

 plant, which accounts for its power, as a file, in polishing wood, 

 ivory, or even brass. This purpose it has long served in En- 

 gland, under the name of Dutch Rushes, being usually import- 

 ed from Holland. So Wheat Straw, whose cuticle contains the 

 same earth in an impalpable state, like others of the natural fa- 

 mily of Grasses, see r. 1. 71, is used, when burnt, to give the 

 last polish to marble. See Introd. to Botany, ed. 6. 62. 



7. E, variegatum. Variegated Rough Horsetail. 



Stem naked, very rough, branched at the base. Sheaths 

 black, with white, membranous, lanceolate teeth. Catkin 

 terminal. 



E. variegatum, Schleich. Catal.2\. Willd. Sp. PI. v. 5. 7. Comp. 



ed. 4. 170. Engl. Bot. v. 28. t. 1987. Hook. Scot. p. 2. 161. 

 E. n. 1678. Hall. Hist. V. 3. 3. 

 E. nudum minus variegatum Basiliense. Bauh. Pin. 16. Prodr. 24. 



Theatr. 250. nof. 



