FORMATIONS AND GUILDS 



CHAPTER I 

 THE FORMATIONS 



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

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

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

 :)istinction between climatic and edaphic formations. 2. The Climatic Formations. 

 . Classificalion. Characteristics of woodland and grassland. The struggle between 

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

 .nd grassland into desert. Characteristics of deserts, ii. Woodhvid Climate. Climatic 

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

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

 ^liiiiate. Climatic conditions for the existence of grasses. Characteristics of grassland 

 limate. iv. MetcoiflUigical Tables. What they tell and what they should tell. 

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

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

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

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



I. CLIMATIC AND EDAPHIC FACTORS. 



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

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

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

 s ivoodlmid, grassland, or desert. It is true that even from a great 

 listance some interruptions of the prevailing monotony may be dis- 

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

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

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

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

 ■ hich, excepting where two districts meet, always belongs to one or 

 ther of the three above-mentioned types. 



Chains of mountains are frequently boundary walls between districts 

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

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

 liat of North \"enezuela b\' the Cordilleras from the grassland of the 



