RECENT INVESTIGATIONS. 23 



and the latter finally gives way before the beech. The Menyanthes community 

 of wet banks is followed by Carex, and this by meadow moor, which yields to 

 birch forest. The latter in turn is replaced by spruce forest, which seems to 

 persist as the climax. The sequence of development in the moor is (1) aquatic 

 formation, (2) Carex moor, (3) hummock moor, (4) peat moor, (5) pine moor, 

 (6) birch forest, (7) spruce forest. In the swamps, the succession is as follows: 

 (1) Potamogeton, (2) Sphagnum-Amblystegium, (3) Menyanthes-Eriophorum, 

 (4) Car ex-Sphagnum, (5) peat moor, (6) birch forest, (7) spruce forest. 



The following are regarded as climax communities, but it seems obvious 

 that the beech forest is the only real climatic climax: (1) rock heath, (2) pine 

 forest on dry sand or on peat moor, (3) spruce forest on shallow shore moors, 

 (4) birch forest on deep moors, (5) woodland along streams, (6) thorn scrub 

 in warm, dry places, (7) beech forest in all other places. The behavior of the 

 beech as the climax dominant is the same in Finland that Steenstrup and 

 VaupeU have shown for Denmark and Fries for Sweden. Hult thought that 

 this does not indicate a change of climate, but merely the return of the beech 

 into areas from which it was largely removed by lumbering. 



Hult (1887:153) also traced the development of the alpine vegetation of 

 northernmost Finland. He found that in the drier places Cladineta and Aleo- 

 torieta finally replaced all other communities, while in moist areas grass and 

 herb consocies passed into communities of dwarf shrubs, or even into a lichen 

 climax. The development everywhere was marked by a transition from more 

 hygrophilous to more xerophilous conditions. The initial stage of succession 

 was determined by the local conditions of colonization. The sequence itself 

 was regarded as everywhere constant; in no place did a backward development 

 take place. 



Warming, 1891. — ^Warming (1891, 1895, 1907) was the first to give a con- 

 sistent account of succession on sand-dunes, and his pioneer studies in this 

 field have served as a model for the investigation of dune seres in all parts of 

 the world. He found that the shifting or white dunes began as heaps of sand 

 formed by tides, waves, and wind; the particles as a rule are less than one- 

 third of a millimeter in diameter. The further growth of such dunes is made 

 possible by sand binders, such as Psamma arenaria, Elymus arenarius, Carex 

 arenaria, Agropyrum junceum, Lathyrus maritimus, Alsine peploides, etc. The 

 last two are found only on the lower dunes, and are sooner or later driven out 

 by Psamma and Elymus, which are especially adapted to the building of high 

 dunes, because of their ability to push up through a cover of sand. Psamma, 

 however, is the most important pioneer, and excels aU others in its ability to 

 collect sand among its tufted leaves, and to grow up through it. Other plants 

 find their way in among the shoots of Psamma and Elymus, and, as the sand 

 becomes more and more fixed, conquer the intervening spaces. The more 

 effectively these two grasses fix the soil, the more they prepare it for other 

 species, which ultimately replace them. Lichens, mosses, and perennials 

 which form tufts or mats, or possess a multicipital primary root, estabUsh 

 themselves at this stage, and the dune passes into a stable or gray dune. 



Warming recognized two principal associations (consocies) among those of 

 the shifting dune, viz, Psammetum and Elymetum. Woody species such as 

 Hippophae rhamnoides, Salix repens, and Empetrum nigrum appear here and 

 there, and give rise to scrub. The gray dune may pass into dune-heath or 



