44 WILD FLOWERS. 



every species of toil, the plant retains its place, and 

 is still imported to this country in considerable 

 quantities from the moist shores and canal banks 

 of Holland. It is particularly the rough-horsetail 

 (E. hyemdle), or a species very closely allied to it,* 

 which is thus imported ; the plant is of immense 

 value in its native country from the extraordinary 

 length and interlaced growth of its root-fibres, which 

 mat together and consolidate the loose and swampy 

 soil in which they grow, and thus form one of the 

 most effectual water-dams of so level a land. A 

 very familiar example of the extraordinary deve- 

 lopment of the roots of the equisetum is, that which 

 we may observe in the marsh-horsetail (E. palustre); 

 the plant that fills and clogs our draining-pipes in 

 such an extraordinary manner as to render closed 

 drainage quite impracticable in localities where it 

 abounds. Insinuating its fibres at every joint of 

 the pipe, they luxuriate in the constant flow of water 

 within, and shoot out to an extraordinary length, 

 intertwining in such a manner, that when the mass 

 is taken out and dried, it might be taken for a very 

 bulky bird's nest. 



The value of this plant in polishing is, of course, 

 due to the silicious substance in its stems, as was 

 first, I believe, positively pointed out by Sir Hum- 

 phrey Davy. The cells incrusted with this silex may 

 be seen by the aid of a microscope, arranged with 

 the most harmonious regularity in those longitudinal 



* Newman, as well as some other botanists, incline to the 

 opinion that it is distinct from the E. hyemdle, or any British 

 species. See " British Ferns," Edit. 2nd. 



