CHAPTER I 



THE CELL 



The cell is the unit of structure of all plants. In fact the 

 cell is the plant in many of the lower forms — so called unicellular 

 plants. All plants, then, consist of one or more cells. 



While cells vary greatly in size, form, color, contents, and 

 function, still in certain respects their structure is identical. 



TYPICAL CELL 



The typical vegetable cell is composed of a living portion or 

 protoplast and an external covering, or wall. The protoplast in- 

 cludes everything within the wall. It is made up of a number 

 of parts, each part performing certain functions yet harmonizing 

 with the work of the cell as a whole. The protoplast (proto- 

 plasm) is a viscid substance resembling the white of an egg. 

 The protoplast, when unstained and unmagniiied, appears 

 structureless, but when stained with dyes and magnified, it is 

 found to be highly organized. The two most striking parts of 

 the protoplast are the cytoplasm and the nucleus. The part 

 of the protoplast hning the innermost part of the wall is the 

 ectoplast, which is less granular and slightly denser than most 

 of the cytoplasm. The cytoplasm is decidedly granular in 

 structure. 



In the cytoplasm occurs one or more cavities, vacuoles, filled 

 with cell sap. Embedded in the cytoplasm are numerous 

 chromatophores, which vary in color in the different cells, from 

 colorless to yellow, to red, and to green. The nucleus is the 

 seat of the vital activity of the cell, and the seat of heredity. 

 The whole life and activity of the cell centre, therefore, in and 

 about the nucleus. 



The outer portion of the nucelus consists of a thin membrane 

 or wall. The membrane encloses numerous granular particles — 



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