164 PLANTS MODIFIED BY THEIR SURROUNDINGS 



little light during the short days of the long winter, and a slight 

 amount of moisture all act upon the vegetation of the arctic region, 

 tending toward very slow growth and dwarfed and stunted form. 



Polar limit of trees, northern Russia. All these trees are full grown, and most of 

 them are almost one hundred years old. 



Vegetation of the Tropics. — A rank and luxuriant growth is 

 found in tropical countries with a uniformly high temperatm-e and 



large rainfall. In 

 general it may be 

 estimated that the 

 rainfall in such 

 countries is at 

 least twice as 

 great as that of 



Limit of ordinary large trees. Ncw Yopk StatC, 



Eegions of the Vine. and in many cases 



Eeglon of Tree-fern,, t^irce tO four timeS 



RegionofPaims. ^s great. An 

 abundant water 



Region of Lichens. 



'^^7^':£-:^-'-^^^^\\ Region of Grasses. 



1-^ '°^"'^^''^^)-'t-°i\ Shrahby Region. 



.-:?..jE....?.rn..:e.e..-s±;° -" -«^ 



1 ') l'('lV/iW'('( V '''''M'''« ■'■^™" "' cinchona trees. 





Plant regions in a tropical mountain. Explain the diagram. Supply, together 



