EQUISETUM. 235 



was in 1833. It lias subsequently been met with in other 

 parts of Ireland,, as well as in Scotland, 



EQUISETUM PALUSTRE, Linnaus. The Marsh Horsetail. 



A common species in boggy places and by the sides of 

 ditches and water-courses. It has a creeping underground 

 stem, which is black and shining, and from the joints of 

 this are produced whorls of slender roots. The part of the 

 stem which rises above ground is erect, growing from a 

 foot to a foot and a half in height. The presence of fructi- 

 fication alone distinguishes the fertile stems from those 

 which are unfruitful ; both being erect, and bearing whorls 

 of numerous branches. 



The stems are somewhat rough on the surface, but less 

 so than in many of the other kinds. They are marked on 

 the exterior by prominent ribs, with intervening broad 

 deep furrows, the number being variable, from six to eight. 

 The joints are invested with nearly cylindrical sheaths, 

 which are quite loose, being almost twice the diameter of 

 the stem in the upper parts of the plant ; the lower sheaths 

 are smaller and rather more funnel-shaped. The sheaths 

 terminate in as many acute wedge-shaped teeth as there 

 are ridges on the stem ; they are pale-coloured, tipped with 

 black or dark brown, and have membranous margins. 



