MANUAL OP NATURE) STUDY. 
97 
make the soil rich and thus nourish the plant. 
Even their bodies when they die decompose and 
become food for plants. 
Summary. 
What plants do for the animals. 
1. Plants furnish ready-made oxygen for ani¬ 
mals to breathe. 
2. Plants gather the elements out of the ground 
and make them over into food for the animals’ sub¬ 
sistence. 
3. Plants hold back the moisture on sloping 
lands and thus prevent arid wastes. By this means 
gushing springs, to slake the thirst of animals, 
burst out at the foot of the hills and bluffs. 
4. Plants furnish protection from storm and 
scorching sun. 
How the animals repay the plants. 
1. Animals yield up carbon dioxide as food for 
the plant. 
2. Animals drain the ground and thus make 
the soil in proper condition for the plants. 
3. Animals (earth-worms) lead the water of 
heavy rain in dry time through the soil to an 
underground outlet, rather than permit it to rush 
away in one general flood and thus do the soil no 
good. 
4. Animals assist in fertilization. 
