232 Floristik, Geographie, Systematik etc. 



January temperature, 4.4° C.) and the summers moist and warm 

 (mean July — Aug. temp., 16.6° C). 



The Lowland Area. The soils consist of recent deposits which 

 form sandhills and mud-flats on the coast, an extensive piain of 

 alluvium margined on the inland side by peat. bogs and fresh-water 

 deposits of gravel, sand, and clay. The coast Vegetation is subdivided 

 into the dune formation, the muddy saltmarsh formation, and the 

 Vegetation of rocky headlands. The dune formation begins as open 

 associations of Salsola Kali and other Strand plants, Tritictiin jiin- 

 ceiini, or AtnjnopJiila arenaria , and reaches the stage of fixed dune 

 with grasses, etc. The development of Vegetation in moist dune 

 hollows is also traced up to an association of dune marsh plants. 

 The plant formation of the muddy salt marsh begins as an open 

 association of Salicoryiia, and after reaching an intermediate asso- 

 ciation of Glyceria [Sclerochloa) maritima and other halophilous 

 plants, the marshes are reclaimed and now form extensive grazing 

 grounds. The "Levels" or piain of Somerset is formed of tidal and 

 other deposits, and is maintained as an area of pastoral grazing 

 country only by an elaborate System of drains and artificial Channels 

 the rieh aquatic Vegetation of which is full}^ described. A series of 

 peat moors lies between the alluvial piain and the ranges of hills. 

 "These probably began their history as associations of aquatic and 

 marsh plants. intermediate associations of Myrica , TetraJix , and 

 Molinia still occur. The final stage is a closed association of Cal- 

 Imiay Much of the original Vegetation has been replaced by farmland 

 or by plantations of Birch and Conifers. Attention is drawn to the 

 author's definition of a plant formation: "It begins its histor\- as an 

 open or unstable plant association, passes through intermediate 

 associations, and eventually becomes a closed or stable association." 

 As an exemple of his System of grouping associations, the succession 

 of the peat moor is given: 



Birch and Pine Farmland of the 



plantations peat moors 



^ ^ 



\ / 



Calluna heath 

 A 



I 

 Myrica, Tetralix and Molima heaths 

 A 

 I 

 Primitive aquatic Vegetation. 



The JJpland Area. This area is almost free from recent deposits 

 of mud, peat, etc., and geological strata are present from the Old 

 Red Sandstone to the Chalk, but the author considers that: "From 

 the Standpoint of Vegetation, it has been sufficient to divide the 

 soils of the upland area into only three classes, sandstones, lime- 

 stones, and deep marls and clays." 



A. The Vegetation of the sandstones. A characteristic of these 

 soils is the easy formation of a surface layer of humus which 

 becomes in time a deeper covering of peat. The ultimate plant 

 association is an oak wood closely related to two forms of oak wood 

 recognised by the author in Yorkshire, the lowland oak wood with 

 Scilla, Pteris and grasses and undergrowth , or the upland drier 

 oak wood with Pteris, Vaccinitnn, Calluna, etc. Uncultivated places 

 not occupied by trees or shrubs are heathlike in character, with 



