394 TROPICAL NATURE 



zones ; while, estimated potentially, in proportion to their life- 

 sustaining power, the lands which enjoy a practically tropical 

 climate (extending as they do considerably beyond the geo- 

 graphical tropics) are very much larger than the temperate 

 regions of the earth. 



Combining the effects of all these various causes, we are 

 quite able to understand the superiority of the tropical parts 

 of the globe, not only in the abundance and variety of their 

 forms of life, but also as regards the ornamental appendages 

 and vivid coloration which these forms present 



