942 



and Potamogeton natans, which form the vegetation; Litorella and the 

 two Isoetes-species are rather unimportant elements. 



d. The limnæ formation of running water. 

 The innumerable short watercourses of the Færoes are fringed 

 as a rule with piants, most of which are mosses. If the water- 

 course is only a seasonal one, then the moss-vegetation may fill it 

 entirely, but in the case of larger and less ephemeral streams, the 

 water runs as a rule over a stony and gravelly bottom, which 

 bears a very sparing lithophyte vegetation (see p. 936). It is only 

 in the larger streams, that one occasionally fmds a meagre vegeta- 

 tion of vascular piants in piaces where the fall is slight and the 

 movement of the water sluggish, that is in the lower reaches 

 of a stream, or in the inlets. The piants which make their ap- 

 pearance under these conditions include those recorded for the 

 lakes, and also certain swamp-plants, but neither the /soéYes-species, 

 nor Siibularia are found in watercourses. As the swamp-plants 

 will be dealt with later, nothing further will be said regarding this 

 formation, except to give some examples, taken from my note- 

 books: 



1. Stream in the Hove-vallej^ on Sydero. An inlet with slight 

 current, and peaty bottom: Litorella and Myriophyllum in abundance, 

 witli Potamogeton poh^gonifolius, Chara delicatula, Callitriche hamulata 

 and submerged Juncus supinus. 



2. Stream at Hojvig in the vicinity of Thorshavn. Water- 

 course with rather rapid flow of water ; in the quieter piaces Potamoge- 

 ton natans with narrow floating-leaves, Myriophyllum, Litorella, Nitella 

 opaca, Juncus supinus and lampocarpus (both submerged). 



3. Stream in the bottom of Kollefjord, near outlet into the 

 sea. Equisetum fluviatile, Callitriche hamulata, Juncus lampobarpus (sub- 

 merged), Litorella and a little Glyceria fluitans. 



4. A stream flowing into Grothusvatn, Sando. Myriophyl- 

 lum and Potamogeton polygonifolius in abundance, with P, nitens and 

 submerged Juncus supinus here and there. 



The plant-associations just described all occur in freshwater. 

 The associations which now come under consideration occur close 

 to the water, or are covered by water occasionally during the year; 

 they are thus a degree less hydrophytic than the first group. There 

 is a marked distinction between the formation existing alongside 

 fresh and running water and that beside stagnant water, hence 

 we recognise two formations: 



