xvi Life and Living Creatures 317 



long cold winters produce a dwarfing effect on vegetation. 

 The Arctic zone of stunted plants leads to the Frigid, and 

 that to the unchanging ice-deserts of the Polar zone. The 

 vertical columns represent slices of 2000 feet of mountain- 

 sides from the region above the snow-line (shown at the top 

 of each column) down to sea-level. The horizontal rows 

 show by their connecting lines at what average height the 

 climate and vegetation corresponding to each of the sea- 

 level zones is attained. Dr. Oscar Drude divides the Earth 

 according to the affinities of its vegetation into three great 

 divisions the Boreal or Northern, the Tropical, and the 

 Austral or Southern. In each one of these the species of 

 plants are closely allied to each other, but distinct from 

 those inhabiting the other divisions. The Austral Group 

 includes the parts of the three southern continents south of 

 the tropic of Capricorn, and falls naturally into an American, 

 African, and Australian division. The flora of Australia 

 is unlike all the others ; there are trees, such as the 

 eucalyptus or gum-tree, which are evergreen but shed their 

 bark yearly ; the wattle (a kind of acacia) and the beef-tree, 

 which bears long green branchlets instead of leaves. The 

 Tropical Group extends from the tropic of Capricorn 

 northward to the Tropic of Cancer in America, to the centre 

 of the Sahara in Africa, and to the Himalaya in Asia. It 

 also contains three main divisions. Cinchona, mahogany, 

 and the cactus are characteristic of the American section ; 

 the oil-palm, baobab, and giant euphorbias of the African; 

 and teak, banyan, and sandal -wood of the Oriental. 

 The Boreal Group is remarkable for the wide range of 

 plants of similar species, such as the pine, birch, and oak, 

 over the Northern division in the three continents in 

 America north of the Great Divide, in Europe north of the 

 southern peninsulas, in Asia the whole northern slopes. The 

 other divisions of this group are the Eastern Asiatic ; the 

 Central Asiatic, comprising the vast plateau region ; the 

 Mediterranean lands, where the olive, mulberry, chestnut, 

 orange, and cork -oak flourish ; and the Central North 

 American, the natural home of maize, tobacco, and the 

 giant pines of California. 



