THE PEAT CLISTASE. 



381 



digyna, Empetrum nigrum, Vacdnium uliginosum, and Hippophae rhamnoides. 

 This gave way to Pop/ulus tremula, together with Salix dnerea, Betula odorata 

 and B. alpestris, which then yielded to Pinus silvestris, with Ulmits montana, 

 Tilia parvifolia, and a large number of shrubs. Following the pine, the oak, 

 Quercus pedunculata, with Alnus glutinosa, A. incana, and Acer platanoides 

 became dominant. Finally Fagus silvatica and Carpinus betula appeared, but 

 at a time when tufa deposits were being no longer formed, as is true also of 

 Picea excelsa. 



According to Fischer-Benzon (1890, 1891), the moors of Schleswig-Holstein 

 show the following layers: 



(1) Reed peat, commonly lowermost, characterized by Phragmites com- 

 munis; (2) meadow peat, with Carex and Hypnum alongside Phragmites; 

 (3) leaf peat, consisting of fallen leaves, fruits, and branches of trees; (4) liver 

 peat, consisting of fallen leaves, bark, etc., with algae; (5) moss peat, consisting 

 of Sphagnum, and often Calluna vulgaris and Eriophorum vaginatum; (6) heath 

 peat, consisting particularly of stems and roots of Calluna, with some Andro- 

 meda polifolia, Scirpus caespitosus, Juncus sqvarrosus, and a few lichens, or, in 

 moister places, with Erica tetralix and species of Carex. The peat-moors may 

 be distinguished as reed-grass moors, Arundinetum, swamp-moors, Caricetum, 

 high moors, Sphagnetum, and forest moors. The depth of the peat varies 

 from 8 to 20 meters. Meadow, swamp, and forest moors are in existence at 

 the present time, but the high moors are for the most part too dry, and only 

 show Sphagnum in the wettest places. The study of the sequence of the 

 layers permits the recognition of the following four periods: (1) aspen, accom- 

 panied by Betula, Salix, and Phragmites in great quantities, together with a 

 large munber of aquatic species; (2) pine period, with a large number of sub- 

 ordinate deciduous trees; (3) oak period, in which the oak is the predominant 

 forest tree, accompa,nied by dense hazel scrub; (4) beech period. For a time 

 the beech and oak Hved together in a mixed association, and then the beech 

 replaced the oak by virtue of its greater tolerance. On the other hand, the 

 beech seems to-day to be yielding before the spruce. 



Sernander (1891) has described the discovery of fossil stumps in the deposits 

 of Axsjon Lake in Sweden: 



UK) ^ 



Figs. 38 and 39. — Sections of a peat stase with stump layers on shores of Axsjon 

 Lake, Sweden. After Sernander. Fig. 38: a, flood area; 6, slime; c, Sphag- 

 nam palustre peat; d, moraines. Fig. 39: a, Sphagnum nemoreum peat; 

 6, slime; c, morainal gravel. 



