374 RIKARD STERNER 



belongs to the phanerogamous » Micro-flora* of shores, which is of great interest, 

 not least in the matter of the distribution conditions of the species. The distri- 

 bution of Elatine exemplifies a type that we have previously encountered on 

 several occasions, inasmuch as the majority of its occurrences fall within the Central 

 Swedish lowlands; but the species is also found in the extreme south of Sweden, 

 and stretches far towards the north in the coast-resion of Norrland. 



Moor species. 



The plant associations which have been brought together under this heading 

 are characterized by the abundance of Sphagna. In other respects they may be 

 of widely different kinds ■ — grass-sedge associations, shrub associations, or forest 

 associations. 



These types of vegetation in Europe are chiefly distributed in the Boreal coni- 

 ferous forest zone. Here they form some of the most important types of vege- 

 tation. 



In the north of Russia Sphagnum associations occupy immense areas (Midden- 

 dorff 1867; Pohle 1903). What causes their appearance in these regions would 

 seem to be the large amount of moisture in the ground (caused by, among other 

 things, the small amount of evaporation), a weak drainage system owing to the 

 flatness of the surface, and soil poor in nutrition. 



The Sphagnum associations have a great distribution towards the south. Ac- 

 cording to Tanfiljev i8go, its boundary coincides approximately with the northern 

 limit of the black earth; but still further to the south there are scattered occur- 

 rences, edaphically caused by moist leached sandy soil and bad drainage. 



The North-East European Sphagnum associations have a floristic character 

 which differs from those of the north-west of Europe. Several species which are 

 important constituents of Sphagnum mosses of the Subatlantic and the North- 

 atlantic flora-provinces are altogether lacking in the north-east of Europe, while 

 on the other hand one or two species falling under this group are confined to 

 the north-east of Europe. Of these last-named species the most important is 

 Ledum palusire. 



This species seems to be highly characteristic of the Sphagnum associations of 

 Middle Russia, as it is found in practically all hsts of species dealing with such 

 associations. [Flerov 1910, e. g. lists 262, 566, 774, 805; Kossinsky 1913, p. 

 121 (Kostroma); Saljessky 1900, p. 169 (Orel); Kultschitskaja and Endaurova 

 1906, p. 43 (Ryazan); Korshinsky 1888 (Eastern Russia); Michajlovskij 1903 

 (Chernigov) etc.] 



