SCANDINAVIA. 245 



to 2 meters above the water, and are found to depths of 2 meters. Typha is 

 usually found outermost, Phragmites innermost. Of the three, Typha is the 

 one which is most readily torn out of place, and consequently grows in more 

 sheltered places. Sdrpus and Phragmites often grow together, one or the 

 other dominating, or the two species sometimes occiu-ring equally numerous. 

 Where the soil is firm, and the action of the waves marked, Phragmites exceeds 

 Sdrpus; where the ground is soft and the depth is 2 meters or more, Sdrpus 

 dominates. The author fm"ther considers the r61e of amphibious plants in 

 the filling up of lakes and in various types of floating vegetation. 



Kruuse (1898) distinguishes the following formations on the west coast of 

 Greenland: 



(1) Willow scrub, typically of Salix glauca; (2) heath characterized by 

 Empetrum and with Vacdnium uliginosum, Loiseleuria, Dryas, and Cassiope 

 as societies; (3) Hydrophilous formations, (a) Sphagnum swamp, (6) moss- 

 Uchen dry areas with Polytrichum, Dicranum, and Pohlia, (c) ponds with 

 Hippurus, Batrachium, Eguisetum, Potamogeton, Sparganium, Heleockaris, 

 Callitriche, etc., (d) shores with Carex. On the west and southwest sides of 

 ponds the vegetation passes gradually into swamp and heath through the 

 following communities : (1) Hypnum, (2) Sphagnum with Cyperaceae, (3) Poly- 

 trichum and Dicranum, (4) Vacdnium, Ledum, and Empetrum. In many 

 valleys, characteristic, small, crescent-shaped ridges are formed by Salix 

 glauca and Carex. These produce small swampy areas in which Cyperaceae 

 and species of Ranuncvlv^ and Saxijraga thrive in particular. Gradually 

 these swampy areas reach such a height that the ridge or dam is broken by 

 the water, the soil dries out, and the heath begins to appear. 



Paulsen (1898) has distinguished one hydrophUe and three psammophile 

 formations in the island of Anholt: 



The strand exhibits white dunes, with Psamma, Elymus, Agropyrum jun- 

 ceum, and the usual halophytes, while in wetter places grow Salix repens, 

 Empetrum, Juncus, etc. In some places a flat stretch of land behind the dunes 

 passes gradually into Erica and Calluna heath. The interior consists of old 

 shore-lines and dunes with Polytrichum as the characteristic plant, and a 

 mixtm-e of open phanerogamic vegetation. Psammn arenaria is the dominant 

 on the dunes in this region. Within the chain of hills is foimd the swamp 

 formation with its usual vegetation. 



Semander (1898) defines as tundra those arctic formations which occur 

 upon dry or little swampy ground, in which the groimd-layer is a closed one of 

 mosses and lichens and the field-layer when present consists of sparse flowering 

 plants. In accordance with the dominance of mosses or lichens, he distinguishes 

 moss or hchen timdra: 



The frequent communities, Cladineta pura and Alectorieta pura of Hult, 

 belong to the Hchen tundra. Moss timdra is relatively infrequent in the region 

 studied, and is represented by Polytrichum-tandra. and DicronMm-tundra. In 

 the typical DicranMm-tundra, the lowermost field-layer consists of abundant 

 dwarf shrubs with sparse herbs and grasses, and the ground-layer of mosses 

 and hchens. It shows transition stages to Sphagnetum, Empetretum, and Salice- 

 tum, but for the most part is regarded by the author as a climax formation. 



Nilsson (1899) has studied the development of vegetation on the cliffs and 

 moors in middle Sweden: 



