THE FACTORS OF DISTRIBUTION 37 



east-central Australia, Venezuela, and southern Brazil, 

 we have the open, park-like area of tall grasses known 

 as Savana. With scanty summer rains in similar 

 latitudes, as in the northern Soudan, Somaliland, 

 Bechuanaland, and central Australia, we get the Scrub- 

 lands, especially characterised by spinous, gum-yielding 

 trees and shrubs such as the Acacias; whilst in the 

 practically rainless areas which accompany the peren- 

 nially high atmospheric pressure and outflowing air 

 along the lines of the Tropics, as in the Sahara, Arabia, 

 Thar, west-central Australia, Kalahari, and Atacama, 

 and in the mountain-girt plateaux in the centre of 

 monsoon areas, as in Gobi, Iran, the Transcaspian 

 region, and the Great Basin of North America, we have 

 Deserts in which vegetation is all but confined to oases 

 surrounding springs. 



In temperate latitudes also we have grassy Steppes, 

 as in Argentina, western New South Wales, northern 

 Persia, south-western Siberia, and the prairie region of 

 the western United States and Canada, where with 

 winter snow we have a small summer rainfall and three 

 types of forest. In the Warm Temperate Zone, from 

 about 30 to 45, we have evergreen forests; but those 

 of western regions, such as the Mediterranean area, 

 south-west Cape Colony, and south-west Australia, have 

 winter rain, and are characterised by such small, dry 

 leaves as those of the olive ; whilst eastern regions, such 

 as China and Japan, the eastern United States, Uruguay, 

 and south-east Australia, have summer rains, the effect 

 of which is seen in the large thick leaves of Camellia 

 and Magnolia. In the Cold Temperate Zone, between 

 45 and 60 in Western Europe, and between 45 and 

 50 in south-eastern Siberia and south-eastern Canada, 

 where summers are warm and wet, we find mixed forests 

 of broad-leaved deciduous trees, followed on the north 

 by the belt of coniferous, needle-leaved evergreens. 



From this it is obvious that nearness to the sea, 

 altitude above sea -level, the direction of prevalent 

 moisture-laden winds, and the presence of mountains 

 which will cause them to precipitate their moisture, 

 profoundly modify rainfall, and thus affect the distribu- 

 tion and character of vegetation. It will also be seen 

 that the season at which rain falls is of the greatest 

 ificance. The hot, dry summers of the Mediter- 



-" 



