PART III— HISTOLOGY, OR THE MINUTE 

 STRUCTURE OF PLANTS 



CHAPTER XXXI 

 THE CELL 



381. THE CELL AS A WHOLE.— All of the higher plants 

 are made up of a large number of bodies or parts called 

 cells. These are so minute that, in most cases, they are 

 invisible to the naked eye. 



382. CELLS ARE OF MANY FORMS.— In general, plant 

 cells may be assigned to some one of the following 

 forms : 



spherical, as in protococcus (a minute alga to be found 

 on damp walls and rocks), and apple flesh; 



polyhedral, or many-sided, as in pith of elder; 



tabular or flat, as in epidermis of leaves; 



cylindrical, as in vaucheria, spirogyra; 



fibrous, as cotton fibers; 



vascular, as the ducts of wood ; 



stellate, as in the interior of leaves of lathyrus (sweet 

 pea) and other plants. 



383. PARTS OF A CELL. — Every living, growing cell 

 contains protoplasm (171), a colorless, semi-fluid sub- 

 stance, which is usually inclosed within a cell-wall. 

 Within the wall, also, and sometimes closely surrounded 

 by protoplasm, is a dense body known as the nucleus. 

 The nucleus usually contains a smaller central part, or 



(233) 



