FORMATIONS AND GUILDS 



CHAPTER I 

 THE FORMATIONS 



i. Climatic and Edaphic Factors. General type of the vegetation determined by 

 atmospheric precipitation. General type of the flora determined chiefly by heat. Details 

 determined by edaphic influences. The formations. Principal and subsidiary members. 

 Distinction between climatic and edaphic formations. 2. The Climatic Formations, 

 i. Classification. Characteristics of woodland and grassland. The struggle between 

 them. Invasion of the Malayan forest by the alang-steppe. Degradation of woodland 

 and grassland into desert. Characteristics of deserts, ii. Woodland Climate. Climatic 

 conditions for the existence of trees. Hygrophilous and xerophilous trees. The 

 limits of tree-growth. Brushwood. Characteristics of woodland climate, iii. Grassland 

 Climate. Climatic conditions for the existence of grasses. Characteristics of grassland 

 climate, iv. Meteorological Tables. What they tell and what they should tell. 

 3. The Edaphic Formations, i. Edaphic Influences in general, ii. Edaphic Formations 

 due to Telluric Water, iii. Open Edaphic Formations. Rocks, gravel, sandy soil, 

 iv. Transition from Edaphic into Climatic Formations. Krakatoa. The volcano 

 Gunter. The Camargue. 4. Life of the Plant-commune in the Formations. 



1. CLIMATIC AND EDAPHIC FACTORS. 



If one looks down upon the flat virgin tract of country from a 

 considerable height, say from the top of a mountain, or better still from 

 a balloon, the character of its vegetation as a rule appears uniform, either 

 as woodland, grassland, or desert. It is true that even from a great 

 distance some interruptions of the prevailing monotony may be dis- 

 tinguished. Where for instance a river traverses the grassy landscape, 

 its banks are frequently clad by belts of forests, or the dry desert 

 shows spots and strips of luxuriant vegetation. These are indeed mere 

 accidents, having no influence on the general character of the landscape, 

 which, excepting where two districts meet, always belongs to one or 

 other of the three above-mentioned types. 



Chains of mountains are frequently boundary walls between districts 

 of dissimilar types of vegetation. Thus the forest district of North 

 Africa is separated by the Atlas Mountains from the Sahara desert, 

 that of North Venezuela by the Cordilleras from the grassland of the 



