THE BRITISH HORSETAILS. 117 



Dutch Rush and Shave-grass. They are obtained from Hol- 

 land, where this species is planted to support the embank- 

 ments, which it does by means of its branching underground 

 stems. It has been suggested that our own sandy sea-coasts 

 might be profitably planted with it. The peculiarity which 

 gives it its commercial value, is the presence of a very hard 

 coating of silex, which is deposited in the form of little crys- 

 tals, rendering the surface rough like a rasp or file, and hence 

 not only woods, but metals and stones may be polished by 

 it. This silicious coating is so entire, and of such density, 

 that it is stated the whole of the vegetable matter may be 

 removed by maceration, or, according to others, by burning, 

 without destroying the form of the plant. The minute crys- 

 tals of silex, of which the flinty coating consists, are arranged 

 with a degree of regularity which, under a microscope, has a 

 very beautiful 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 polisi 

 ing ; but the stems of the E. hyemale are much preferable t 

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

 more hardened surface. 



MR. MOORE'S ROUGH HORSETAIL. 



This is the Equisetum Moorei of Newman. It differs from 

 the other native unbranched Horsetails in the nature of its 

 stems, which are not persistent through the winter, or ever 

 green, as they are, but die down in autumn, and are renewed, 

 they are therefore annual. They grow a foot and a half to 

 two and a half feet high, and are unbranched, except where 

 the apex has been destroyed, in which case branches are 

 sparingly produced. They are rough, and are channelled 

 with about twelve deep well-marked furrows. The sheaths, 

 which are loose, and have the same number of ridges as the 

 stem, are whitish, with a black ring at the base and tipped 

 by about twelve blackish teeth, which are rigid, bluntish, 

 and terminated by elongated membranous paler awns. 



This plant was found growing on banks facing the sea at 

 Eockfield in the county of Wicklow, in the year 1851, by Mr. 

 D. Moore, Curator of the Royal Botanic Gardens at Glasne- 

 vin, Dublin. 



