FEKN ALLIES. 51 



In this species the stem is smooth, the cone ripens in 

 July, and then falls off. 



Swaledale furnished our specimens of the Marsh Horse- 

 tail (E. palustre), its stems are deeply furrowed, and it 

 has from four to eight branches in a whorl, the branches 

 becoming much shorter as they near the summit. It is 

 a slenderer plant than any of the others which we have 

 described, its whorls more distant, its branches fewer and 

 slighter in form, the cone dark coloured and small, and 

 the tint of the whole plant a darker green. There is a 

 variety bearing cones on the upper branches, called Poly- 

 stachion, and one with naked stems, called Nudum, but 

 we have not found either of these. 



On the borders of mountain streams in the Yorkshire 

 dales we have occasionally met with the naked stems of 

 the Kough Horse-tail or Shave-grass. The stems are of a 

 glaucous green, very rough from the presence of a large 

 quantity of the silex crystals, minutely striated, and bear- 

 ing a small cone. This plant is imported from Holland 

 for polishing wood, ivory, and metal ; it forms a natural 

 file. Mr. Baird, in his " Flora of Berwickshire," tells us 

 that "the dairy- worn en of Muiroick and Chipchase, where 

 the plant is plentiful, use it for smoothing their milk- 

 vessels." 



The Quill- wort (Isoetes lacustris, jig. 7) is a curious 

 plant, and also ranked by most authors as a Fern Ally. 

 Here the seed is contained in vessels embedded at the 

 base of the leaves. It always grows submerged. Our 

 specimen came from the Westmoreland lakes. 



The Pill-wort is an equally curious plant, bearing its 

 seeds in round hard balls attached to the stem. The 



