552 A. HESSELBO. 



slopes. There they lie irregularly scattered in bright-green patches, 

 differing greatly in size, and conspicuous even at a distance 

 bv their colour which is distinct from that of their surround- 



is 



ings. Higher up on the slopes at the foot of the bluffs, they fre- 

 quently form continuous belts in connection with the mossy fringe 

 along the downward - flowing streams (Helgi Jonsson, 1900, 

 p. 25). 



The vegetation consists of nearly the same species as those 

 found on inundated gravelly soil, and the external conditions for 

 the plants are also essentially the same in both places, since it is 

 the cold, well-aerated water which determines the composition of 

 the vegetation. During summer the temperature of the water is 

 usually only 4 5, and this low temperature acts as a great 

 check to the growth of higher plants, and is therefore indirectly 

 favourable to the moss vegetation. The difference between the two 

 vegetations is especially due to the substratum, that of the vege- 

 tation of inundated ground and stream-banks consisting of gravel, 

 while the moss bog developes on mud. For this reason also, some 

 of the species which occur in the gravelly soil are absent from the 

 moss-bogs proper, for instance Hypnum falcatum, H. decipiens, Di- 

 cranella squarrosa, Philonotis seriata, Haplozia cordifolia, Scapania 

 pahidosa and Chiloscyphus polyanthus var. fragilis. 



On flat ground moss bogs are, as a rule, almost circular in 

 shape, and the species are arranged concentrically around the point 

 of issue of the spring, whence the water gradually oozes through 

 the moss carpet, and spreads out over the surrounding boggy 

 ground. On sloping ground the moss bog is usually oblong in 

 shape, and the spring emerges at its upper end (Fig. 19). 



In the majority of cases the Bryophyte vegetation near springs 

 (the Dy) is a Philonotis-Mniobryum association, in which other species 

 of Bryophyta and a few higher plants occur scattered (Ostf., 1907, 

 p. 69). On the soft mud around the point of issue of the spring 

 - and often covering the latter - Mniobrynm albicans var. glacialis 

 usually grows, and outside the latter there is a broad belt of Phi- 

 lonotis fontana, which may be intermixed with or replaced by other 

 mosses; and scattered in the moss carpet are a few flowering plants 

 and vascular cryptogams, especially Montia rwularis , Saxifrage 

 stellaris, Epilobinin spp. and Eqnisetam palnstre. 



