CHAPTER X 



EDAPHIC INFLUENCES IN THE 

 TEMPERATE ZONES 



i. General Considerations. 2. Temperate Littoral Formations. Littoral swamp, 

 littoral meadow, dunes. 3. Heath. Calluna vulgaris. Conditions of existence. Com- 

 panion-plants. 4. Moors. High-moor and meadow-moor. Sphagnum. Conditions of 

 nourishment. Carnivorous plants of the American moor. 



1. GENERAL CONSIDERATIONS. 



Frequent reference has been made throughout this section of the book to 

 the share which the soil takes in the oecology and composition of the forma- 

 tions. Attention was drawn to pine-forest, which on permeable soil replaces 

 broad-leaved forest, to swamp-forest, which in North America covers badly- 

 drained, wet soil (Figs. 48 and 392), to the increasing luxuriance of all 

 forest formations near rivers and lakes, where the moisture of the soil is 

 increased by infiltration. The increase of the subterranean water operates 

 still more strikingly in grassland districts, where it causes the occurrence of 

 fringing-forests along the banks of rivers and of patches of forest in depres- 

 sions of the ground, and in deserts, where it often evokes, as if by magic, 

 a luxuriant picture of vegetation. Finally, the fundamental importance of 

 edaphic influences was mentioned in connexion with transitional districts, 

 where, for example, slight differences in the nature of the soil determine 

 whether it shall be woodland, grassland, or desert. 



In the cases cited climate and soil are so intimately associated that 

 a separate treatment of the factors of both would have been unnatural 

 and confusing. It is otherwise with edaphic formations of sharply limited 

 local occurrence, whose character remains essentially identical, in either 

 a woodland climate or a grassland climate, to some extent also in a desert 

 climate, and which represent independent phenomena in the various dis- 

 tricts. Amongst these formations are included, with others, sand and sili- 

 cious formations in and along river-beds. As these formations possess in all 

 climates essentially the same oecology, and as this has been already described, 

 no further reference will be made to this group of formations. It may be 

 merely mentioned that the low cushion-plants, in particular the species of 

 Raoulia in New Zealand, which are characteristic of cooler districts of the 

 south temperate zone, occur very frequently in dry pebbly beds of water- 

 courses (Fig. 393). 



More characteristic are the formations of the sea-shore, which in the 



