LESSON FOUR 
PLANTS AND ANIMALS 
1. How plants grow.—Plants secure food from the soil 
and air. An animal frame comprises the essential con- 
stituents of plants, with sodium and chlorine in addition. 
Animals cannot subsist directly on the soil and air. Their 
food consists of plants or of other animals that subsist 
directly or indirectly in plants. Plant life is the founda- 
tion of growth and energy. 
The soil, the plant, and the animal represent the three great fields 
of agricultural activity. They are dependent upon one another, each 
giving to or receiving from the others the things vital to its very 
existence. Without a soil there would be, of course, neither plant 
nor animal life; without plants there co ‘ld be no: animals; and 
without plants or animals there would be a useless if not a barren 
soil. The first step is plant growth, whereby the elements essential 
to all growth are organized in plant cells, compounds and tissues. 
On this plant tissue the animal feeds. After the animal dies, with 
its decay and decomposition, come the changes of animal tissue back 
to soil and air—back to the original materials such as they were be- 
fore captured by roots and leaves and formed into plants. It is in 
this manner that the plant grows out of soil and air, the animal out 
of plants and air, and the soil out of plants and animals. The animal 
when living contributes active supplies, and when dead both humus 
and mineral ingredients are returned to the soil; the soil thus re- 
inforced favors the new plants now growing in it; and the new 
plants, now abundantly nourished, more effec- 
tively take care of the animals. From the plant 
is fed the animal; from the animal is sustained 
the soil; from the soil is nourished the plant. 
2. Cells—A plant or animal is 
formed of myriads of cells. These in- 
(e)(©) crease in number as an_ individual 
grows. Simply stated, the cell is an 
How Ceits Grow — inclosed sac within whose walls are the 
Growth of asingle cell, juices and other substances required for 
ending in cell division or 
the production of two 
Paige ee growth and development, The cell 
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