EQUISETUM. 229 



metals and stones may be polished by it. This siliceous 

 coating is so entire, and of such density, that it is stated the 

 whole of the vegetable matter may be removed by macera- 

 tion, or, according to others, by burning, without destroy- 

 ing the form of the plant. The minute crystals of silex, of 

 which the flinty coating consists, are arranged with a degree 

 of regularity which, under a microscope, has a very beauti- 

 ful appearance ; they form a series of longitudinal elevated 

 points, and in the furrows between them are cup-shaped 

 depressions, at the bottom of each of which is placed a 

 stomate or pore. 



All the species of Equisetum have a flinty coating to their 

 stems, and may be, and are, more or less employed in polish- 

 ing ; but the stems of the E. Jiyemale are much preferable 

 to those of the other kinds, in consequence of their rougher 

 and more hardened surface. 



EQUISETUM LIMOSUM, Linnaeus. The Water Horsetail, 

 or Smooth Naked Horsetail. 



This is a common species and generally distributed, 

 occurring principally in pools, ditches, and marshy places, 

 though occasionally in running streams. It is rather a 

 tall-growing plant, the stems rising from two to three feet 

 or more in height, springing from the joints of the dark 



