CHAPTER IX. 

 THE CELL AND TISSUE. 



1. Sections taken from the various parts of the plants are 

 shown by the aid of the microscope to consist of small sac- 

 like bodies (Fig. 93). These structural units are called Cells. 

 Those which are isolated, as pollen grains, spores of Smut, etc. 

 are nearly or quite globular; so also are the cells of pith. 



Fig. 93. 



Fig. 94. 



But in stems they are usually crowded closely together, and 

 become many-sided by mutual pressure ; they are often also 

 much elongated. In leaves the outer la5'er of cells is com- 

 pact; in the interior they are sometimes nearly globular, or 

 often quite irregular in shape ; there are comparatively large 

 spaces between them. Occasionally cells are star-shaped, as 

 in the tissue of the Rush (Fig. 94). Sometimes they are very 

 irregular and branching, as in the common Moulds. 



While a laboratory and compound microscopes are indispensable for a full 

 and satisfactoiy study of cells and tissue (which, however, belongs to an ad- 

 vanced course in Botany), yet by the aid of figures in the text, and the 

 help of a good pocket lens, the essentials of this portion of the subject may 

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