Where Has Nature Spread the Forest? loi 



vegetation is so dense and rank that you can hardly travel 

 through it. Such foregts are found in the tropical parts of 

 the country. Where little rain falls there is scanty vege- 

 tation, as upon the deserts of the Southwest. But where 

 it is very cold, even if there is much snow or rain, you will 

 find no trees. 



We must not forget that there is another thing that af- 

 fects the growth of trees, and that is the soil. Pines like 

 a sandy soil, while most other trees do not. Certain cedars 

 and cypresses like swampy places where no other trees will 

 grow. Many beautiful meadows and prairies have no trees, 

 because the soil is not well drained. 



It is very easy to understand why trees cannot grow 

 where it is dry, but how shall we learn of the effect of cold 

 upon them ? Shall we have to take a Journey of thousands 

 of miles into the far North, until we finally come to the land 

 called the Barren Lands or tundras, where the trees become 

 sttmted and at last disappear — a land where they cannot 

 longer fight against the cold and live ? 



Fortunately such a long journey is not necessary. All 

 we have to do is to climb a great mountain range, like the 

 Sierra Nevadas, to pass through all the different climates 

 which we would experience on a long journey to the arctic 

 regions. 



It is only a few miles from the hot San Joaquin Valley, 

 at the base of the Sierras, where it is so dry that irrigation 

 is necessary, to the summit of the range, where the winter 

 climate is as cold as it is in the arctic regions. 



In going up the mountains we first come to the foothills, 

 where there is a little more rain than in the valley. Here 

 we find oak trees growing. Farther up there is still more 



