3 i6 



The Realm of Nature 



CHAP. 



developed in a region formerly of uniform configuration and 

 climate, similar plants may become separated by quite 

 different species produced by the new conditions. While 

 all animals are absolutely dependent on plants for food, 

 some plants are in great part dependent on animals for their 

 continued existence, and bright flowers, perfumes, and honey 

 have an important office in attracting them. Insects especi- 

 ally carry pollen from one flower to another, and so secure 

 cross fertilisation, which greatly improves the strength of 

 the seed. 



405. Floral Zones. Speaking widely, the luxuriance 

 and variety of vegetation decrease from the equator to the 

 poles, and from sea-level toward the summit of mountains. 

 Fig. 63, adapted from Smirnoff's Russian Physical Geo- 



V. COOL TEMPERATE 



__ 



IV. WARM TEMPERAT 







III. SUBTROPICAL 







II. TROPICAL 



I. EQUATORIAL 

 FIG. 63. Zones of climate and vegetation in latitude and altitude (after Smirnoff ). 



graphy, represents a quadrant of the Earth's surface divided 

 into climate zones at sea-level. The Eqitatorial zone corre- 

 sponds to the region of maximum heat and rainfall ; the 

 Tropical to the region of maximum heat and small rainfall. 

 The Subtropical, Warm Temperate and Cool Temperate 

 zones show a gradual transition to the Subarctic, in which 



