202 



WHEKE PLANTS GROW 



peat. When dug out and dried, i)eat may be used as fuel. 

 Finally it may decay and make a vegetable soil known as 

 muck. When thoroughly decayed, plants become vege- 

 table mold or humus. New plants grow on peat or 

 muck, and the accumulations year by year tend to raise the 

 level of the bog, and the surface may finally become so 

 high as to support plants of the high lands. The chief 

 agent in the formation of peat bogs is sphagnum moss. 

 New moss grows on the old, and the bog becomes higher 

 as time goes on. Fig. 347. 



337. PLANTS CONTRIBUTE TO SCENERY. — Aside from 

 sky and air, natural scenery depends chiefly on two things: 

 the physical contour of the earth ; the character of the 

 vegetation. Attractive landscapes have a varied vegeta- 

 tion. Imagine any landscape with which you arc familiar 

 to be devoid of plants. Compare Figs. 348 and 349. 



Eeview. — What is meant by environment? By habitat? Flora? 

 What determines where plants shall grow? What is an aquatic plant? 

 Explain immersed, emersed, free-swimming. What is plankton? Ex- 

 plain terrestrial. Amphibious. Why are some plants rare or local ? 

 Why are some plants common? Name some unusual places in which 

 you have seen plants growing. Give examples of how plants occupy 

 the new places. How do plants aid in the formation of soil ? Explain 

 what is meant by peat, muck, humus. How are peat bogs formed ? 

 Wliat relation have plants to scenery ? 



