266 HISTORY OF BRITISH FERNS. 
not providing during summer a supply of this plant and of 
the Reindeer Moss, for winter use; thus making some 
provision for their herds at a time when the ground is 
covered with frost-bound snow, so as not to risk the loss of 
their most valuable or entire possessions. An instance is 
related by Mr. Knapp, in which a colony of the short-tailed 
water-rats made this plant their food, and in the evening 
might be heard champing it at many yards' distance. 
Equisetum palustre, Linnaeus. 
The Marsh Horsetail. 
A common species in boggy places, and by the sides of 
ditches and watercourses. 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 aboveground is erect, growing from a 
foot to a foot and a half in height. The presence of fruc¬ 
tification 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 
