Floristik, Geographie, Systematik etc. 117 



stone grassland association (Festucetum ovinae). The sub-formation 

 of the Chalk is distinguished by a beechwood and an ashwood asso- 

 ciation, with Taxus; the grassland association is the chalk pasture 

 so typical of the South Downs. On marls and calcareous sand- 

 stones, the woodland is ash-oak-wood and its derivative the ash-oak- 

 hazel copse. 



Aquatic Vegetation (chap. VII) and marsh Vegetation (chap. VIII) 

 are dealt with briefly. A short account of the distribution of the 

 British freshwater phytoplankton is included. 



Several chapters (IX — XII) are devoted to the Vegetation of peat 

 and peaty soils. Three plant -formations are recognised — heath, 

 moor, and fen. The heath-formation includes the plant associations 

 existing on shallow dry peat (Trockentorf}. Moor and fen are used 

 here to designate two formations on deep peat. The fen formation 

 occurs over tracts of peat laid down in the upper parts of tidal 

 estuaries and round freshwater lakes fed by water relatively rieh 

 in lime and other salts (i. e. Niedermoor acc. to Weber); the typical 

 area is the "Fen district" of East Anglica. Moor (Hochmoor) soils 

 are fed by waters poor in mineral salts and are characteristically aeid. 

 The relations of fen Vegetation to aquatic Vegetation (chap. X) have 

 been worked out in considerable detail in the district of the Nor- 

 folk Broads, and the summary is usefully illustrated to show the 

 distribution of characteristic species. 



The moor formation presents two extremes: lowland and upland 

 moors. The lowland moors (chap. XI) are of aquatic origin and 

 some have passed through a stage of fen ; types are described from 

 North Lancashire and the New Forest (Hampshire). The 

 description of the upland moors, mainly those of northern Eng- 

 land, includes a brief discussion of degeneration of moorland 

 (chap. XII). 



Arctic-alpine Vegetation (chap. XIII) includes the plant-forma- 

 tions in which oeeur many species with a limited distribution, ge- 

 nerally at high altitudes. The ecological conditions are discussed 

 at some length and three formations are recognised: a) arctic-alpine 

 grassland, b) formation of the mountain top detritus, c) arctic-alpine 

 chomophyte formation. The grassland formation, with Alchemüla 

 alpina as a characteristic plant, lies beyond the woodland zone and 

 the closed associations of moor and heath. The formation of the 

 mountain top detritus occurs on plateaux and slopes where the 

 surface is mainly rock weathered under the influence of frost and 

 wind; the Vegetation in its early phases is scanty, but may attain 

 to a closed stage, the Rhacomitrium heath. The chomophyte for- 

 mation is limited to places where rocks are exposed as crags and 

 in ravines, and it presents different features aeeording as the rock 

 weathers rapidly or slowly. 



The Vegetation of the sea-coast is dealt with in considerable 

 detail (chap. XIV). The formations recognised are the salt- marsh 

 and the sand dune, the chief plant-associations being described. A 

 special part refers to the plant-communities of shingle-beach, a type 

 of British Vegetation hitherto undescribed. 



A feature of the book is the use of diagrammatic summaries which 

 indicate the author's views as to succession and relationship of the 

 various plant-associations. The relationship of the fourteen British 

 plant-formations is illustrated in a folding diagram; they are grouped 

 mainly aeeording to the soil-habitat and distribution in altitude. The 

 illustrations are photographs or diagrams of types of Vegetation and 



