CHAP, xcvi SUCCESSION OF VEGETATION 



359 



Oenanthe Phellandrium, Iris, Butomus, Acorns, and Equisetum limosum. 1 

 Gradually reed-swamp gives way to low-moor. 2 The bed of the water 

 continues to rise, thanks to species of Carex and other plants belonging 

 to low-moor. When it has been raised so high that the water is 

 filled up to or even above its level with plants and their remains, then 

 in the peat-like soil of the marsh one finds several grasses, also mono- 

 cotylous and dicotylous herbs. Thus arises meadow, which, however, in 

 most cases becomes bushland (with willow-bushes and alder-bushes) and 

 forest, if it be not disturbed by the hand of man. 3 



The developmental succession does not necessarily proceed along the 

 exact lines just indicated. Low-moor may give way to Sphagnum-moor, 

 as it is colonized by Sphagna which continue the development 4 ; the 

 Sphagnum-moor builds itself up on top of the marsh-moor, constantly 

 rising in height far above the water-table. Development does not neces- 

 sarily stop at this stage. The drier soil becomes fitted for other plants, 

 and particularly for woody plants ; Sphagnum-moor that is dried from 

 any cause leads the way to ling-heath, as Calluna, species of Vaccinium, 

 and other heather-plants invade the drier surface. 5 A moor thus converted 

 into heath, 100 square kilometres in extent, occurs in the north of Jut- 

 land. Finally, such ling-heath may give way to forest, as Betula and Pinus 

 sylvestris make their entrance. If the soil be rendered dry, possibly by 

 artificial means, these trees may be replaced by others, such as Picea 

 excelsa and Quercus. 6 



Another type of development is witnessed when the water-level 

 suddenly and considerably falls. Feilberg has given an example of this. 

 When Lake Soborg in Seeland was artificially emptied its original marsh- 

 vegetation, including Menyanthes, Phragmites, Equisetum limosum, and 

 others, was first displaced by Carex acutiformis, Agrostis vulgaris, and Poa 

 trivialis. As the moisture diminished Poa pratensis occupied large tracts, 

 but in turn was vanquished by Festuca rubra. If the soil be brought under 

 cultivation, as the subsoil is loosened and the soil covered with a thin layer 

 of loam, fodder-grasses, including Dactylis glomerata, Festuca elatior, 

 and Poa trivialis, as well as Trifolium repens, make their entrance. 



On moraine-soil in northern Europe many small moors have been 

 produced in small lakes and pools that arose at the Glacial Epoch. 

 Beneath the moor is a thin layer of clay which arose from the mud washed 

 from the neighbouring elevations. In this are deposited numerous remains 

 of the subglacial tundra-vegetation, which arose on land immediately after 

 the Glacial Epoch, and was the Dryas-vegetation, consisting of Dryas 

 octopetala, Salix reticulata, S. polaris, Betula nana, Oxyria digyna, 

 Arctostaphylos alpina, Polygonum viviparum, and others. These fossil 

 remains were discovered in 1870 by Nathorst in Schonen, later in Den- 

 mark and other countries. In these water-filled depressions the following 

 was the course of development. Plankton and limnaea-vegetation first 

 developed, and at the margin reed-swamp or moor (with Sphagnum and 



1 In regard to the British Isles see Scott-Elliot, 1900. * See Chap.XLVII. 



1 See p. 217. 4 See Chap. XLIX. * See Chap. LII. 



' In regard to developmental succession of this kind see Klinge, 1890 ; Steen- 

 strup, 1841 ; Kerner, 1863 ; Hult, 1881 ; Magnin, 1893, 1894 ; Stebler and Schroter, 

 1892 ; Weber, 1894; Ffiih and Schroter, 1904; Grabner, 1909 ; and C. MacMillan, 

 1893, 1896. 



