60 THE WORLD OF LIFE 



the eastern slopes of the Andes to beyond tlie southern tropic; 

 while all along the Atlantic coast there is a belt of equal lux- 

 uriance, spreading out again in the extreme south of Brazil 

 and Paraguay to about 30° of south latitude. We could thus 

 travel continuously for about five thousand miles from Mexico 

 to northern Argentina in an almost unbroken tropical forest, 

 or about the same distance down the Amazon valley to Par- 

 anahyba in northern Brazil, and then, after a break of a few 

 hundred miles, along the east coast forests for about two thou- 

 sand miles more. This probably equals, if it does not surpass, 

 the tropical forest area of the rest of the globe. 



We must also take into account the fact that, as a rule, 

 tropical forests differ from those of the temperate zone in the 

 s^^ecies not being gregarious, but so intermingled that adjacent 

 trees are generally of distinct species, while individuals of the 

 same species are more or less widely scattered. When, from 

 some commanding elevation, we can look over a great extent 

 of such a forest, we can usually see, at considerable intervals, 

 a few, perhaps a dozen or more, small patches of identical 

 colour, each indicating a single tree of some particular species 

 which is then in flow^er. A few^ days later we see a different 

 colour, also thinly scattered; but in the region of the most 

 luxuriant tropical forests we never see miles of country thickly 

 dotted with one colour, as would often be the case if our Euro- 

 pean oaks or beeches, birches or pines, produced bright-col- 

 oured flowers. This fact would alone indicate that the tropical 

 forests are wonderfully productive in species of trees and woody 

 climbers, and hardly less so in shrubs of moderate size, which 

 either live under the shade of the loftier trees or line the banks 

 of every river, stream, or brooklet, or other opening to which 

 the sun can penetrate. In those latter positions there is also 

 no lack of herbaceous plants, so that the whole flora is exceed- 

 ingly rich, and the species composing it rapidly change in 

 response to the slightest change of conditions. 



The difficulty of collecting and preserving plants in these 

 forest-clad areas is so great, and the number of resident bot- 



