482 PLANT GEOGRAPHY 



the Kongo and of the Amazon. The rainy forests of the tropics 

 contain extraordinary numbers of species. For example, near 

 Lagoa Santa in Brazil, in an area of three square miles, there are 

 found about four hundred species of trees. Xerophytic plants, 

 many of them with extremely complete adaptations for support- 

 ing life for long periods without water, are characteristic of 

 tropical deserts, while many of the. most decided hydrophytes 

 among land plants are found in the dripping sub-tropical forest 



FIG. 867. Hills of drifted sand in the Sahara 

 After W. M. Davis 



interiors. Throughout a large part of the belt, reaching five 

 degrees each way from the equator, there are daily rains the 

 year round. 



461. Vegetation of temperate regions. We are all familiar in 

 a general way with the nature of the plant life of the north tem- 

 perate zone ; that of the south temperate is in most ways similar 

 to our own. Most of the annuals and biennials are of a medium 

 type, not decided xerophytes nor hydrophytes, and the peren- 

 nials are mainly tropophytes. There are no desert areas so large 

 or so nearly destitute of plants as those found in sub-tropical 

 regions, neither are there any such luxuriant growths as occur in 

 the rainy forest regions of the tropics. On the other hand, the 

 largest trees on earth, the giant redwoods, or Sequoias (Fig. 33), 

 occur in the temperate portion of North America, along the 

 Sierra Nevada, and the taller, though less bulky, gum trees 

 (Eucalyptus) of Australia grow in a warm temperate region. 



