CHAPTER III 
THE CELL 
When a portion of a plant is examined under a microscope, 
it is found to consist of a number of small, boxlike compartments 
called cells. A typical plant cell is shown in Fig. 10, and a section 
of a group of cells in Fig. 11. A 
plant cell is surrounded by a firm 
wall called a cell wall, which may 
be regarded as a container in 
which the protoplasm, or living 
part of the cell, is found. Cells 
may be thought of as the funda- 
mental units of all living things, 
whether plants or animals. The 
cell is the smallest unit of living 
matter capable of continuous in- 
dependent existence and of repro- 
duction. Very small plants or 
animals may consist of only a 
single cell, while large individ- 
uals are composed of a great 
many cells. An egg of either a 
plant or an animal consists of a 
single cell, which, by division 


Fig. 10. A typical cell from a hair 
of a squash plant. (x 180) 
and growth, develops into a mature individual of its species. In 
highly developed plants and animals cells become specialized 
and suited. to different uses. Thus, in ordinary green plants 
there are cells that are especially suited to the absorption of 
water; others, to the conduction of water; and still others, to 
the manufacture of sugar from carbon dioxide and water. The 
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