88 
W. Watson. 
IV. The fourth zone is characterised by two alternative facies 
dominated by distinct species of mosses. The dominant moss by 
the margins of the smaller channels is Sphagnum subnitens, but by 
the sides of the more definite tributaries where there is a slow but 
constant current, it is almost entirely replaced by Hypnum inter¬ 
medium ; one of the reasons for this is that the latter moss requires 
a more constant water-supply, as it is not adapted to take up such 
a large amount of water when it is available as the former. 
IV A. Facies of Sphagnum subnitens. Immediately above the 
Aneura midtifida zone, about 2 cms. above the general level of the 
water, various species of Sphagnum appear. The dominant one is 
5. subnitens , especially its colour-variety violascens, but other Sphagna 
are also present. Cephalozia connivens is usually intermixed with the 
shoots of the Sphagnum , and Calypogeia fissa is also abundant, 
the latter being often very much drawn and with small leaves 
decurrent to a considerable extent when shaded by a quantity of 
overlying Sphagniun , and in this condition is a form analogous to 
the var. aquatica of C. trichomanis (Fig. 7 B). Pinguicula lusitanica, 
Narthecium ossifragum and all three British species of Drosera are 
frequent— D. rotundifolia is the most frequently noticed, not only 
on account of its relative abundance, but also owing to its more 
superficial position. 
The plants occuring in this facies are as follows :— 
Viola palustris f 
Hydrocotyle vulgaris f 
Pinguicula lusitanica o 
Scutellaria minor o 
Narthecium ossifragum f 
Sphagnum subnitens d 
„ rufescens f 
Calypogeia fissa a 
Drosera anglica f 
„ rotundifolia a 
„ longifolia f 
Mentha aquatica o 
Rhynchospora alba o 
Hypnum intermedium o 
Cephalozia connivens a 
IV B. Facies of Hypnum intermedium. Sometimes the 
Sphagnum subnitens facies is not well marked, or it maybe replaced by 
a zone in which species of Hypnum are abundant, this being especially 
well-shown by the sides of slowly running water. The floristic 
composition of this facies is shown in the following list:— 
Viola palustris f Glyceria plicata I 
Pedicularis palustris f Equisetum maximum o 
Hydrocotyle vulgaris a (a in or near alder thicket) 
Galium uliginosum a ,, palustre a 
„ „ var. Witheringii I „ „ var. polystachyumo 
„ palustre 1 „ limosum 1 
Mentha aquatica a Sphagnum subnitens o 
Narthecium ossifragum f „ rufescens o 
