THE HORSETAILS 121 



species, and it is only now and again that even 

 a single branch is produced from the base of one 

 of the sheaths. There is a strong resemblance 

 between the barren and the fertile stems. These 

 are both tall and very erect, usually running up 

 to the height of two or three feet. The stem is 

 very rough to the touch, and is marked with 

 from fourteen to twenty ridges. The edges of 

 these ridges are thickly covered with flinty Dar- 

 ticles. The sheaths of the Dutch Rush clasp 

 the stem of the plant very closely. The fertile 

 cone is small, and is placed at the top of the stem. 

 The Rough Horsetail is not a very common 

 species, but is abundant on the Continent, es- 

 pecially in Holland and Germany, where it is 

 largely employed for the fixing of the soil of 

 embankments. The Rough Horsetail is very 

 useful for polishing wood. 



