COMMON QUILLWORT. 129 



representatives of the genus ; that is to say, British politically, 

 for one is found only in the Channel Islands. 



The name is from two Greek words, isos, equal, and etos, 

 the year, signifying that the plant is to be found in all seasons. 



Common Quillwort (Isoetes lacustris). 

 The Quillwort or Merlin's Grass is not a well-known plant. 

 There are two reasons for this : one is that it is restricted to 

 the northern half of Britain, and the other that it grows on 

 the bottoms of lakes among the mountains. It has a rosette 

 composed of stiff awl-shaped leaves, of which there are from 

 about twelve to twenty. They are as much as six inches long, 

 but often shorter, of a dark-green colour, and, although awl- 

 shaped, there is a suggestion of four-sidedness. The base 

 is very broad and flat. The leaves are pierced with four tubes 

 through their length, and these tubes are divided at intervals 

 by transverse partitions. The megaspore is covered with blunt 

 tubercles, produced by extrusion of the inner coat through the 

 outer coat. The plant is in fruit from May to July. (Plates 141, 



1 43-) 



Its southern range extends only to North Wales and Shrop- 

 shire ; it occurs also in Ireland. In the Scottish Highlands it 

 has been found at an elevation of 2000 feet. On the Continent 

 it is found north of the Alps and in Western Siberia ; it also 

 inhabits North America. 



A large form with leaves a foot and a half long (var. moref) 

 has been found in deep water in Co. Wicklow. 



A sub-species, regarded as distinct by some authorities under 

 the name of Isoetes echinospora, has paler, more spreading 

 leaves, with the sporange almost embedded in the leaf-base 

 and the tubercles of the microspore longer and more sharply 

 pointed. 



The name lacustris is from the Latin lacus, a lake, and 



