PRIMER OF PRIMERS. 181 



in its plant growth, or produces a particular vari- 

 ety of plants called its flora. 



The differences in the distribution of light, heat, 

 and moisture in different parts of the earth cause 

 corresponding differences in the flora of such parts. 



The flora of the equatorial regions consists of 

 such plants as are hest fitted to exist under the 

 conditions of abundant heat, light, and moisture 

 of these regions. 



In passing from the equator to the poles the 

 differences in the distribution of heat and moist- 

 ure cause corresponding differences in the variety 

 and luxuriance of plant life. 



In passing from the base to the summit of a 

 high tropical mountain similar differences in the 

 variety and luxuriance of plant life are noticed, as 

 in going from the equator to the poles. 



Seed-time and harvest seldom fail in nature, 

 because the germs of vegetable life are generously 

 scattered in all regions of the earth. 



The agencies provided by nature for widely 

 scattering the seeds of plants are various. Some 

 seeds are provided with delicate hair-like wings, 

 which permit the wind readily to carry them great 

 distances from the plants which produced them. 

 Others are provided with hooks or bristles, which 



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