PROTOPLASMIC CELL CONTENTS 3 



A cell is a mass of protoplasm containing a nucleus. 



Protoplasm is the more or less semi-fluid, viscid, foamy, and granu- 

 lar substance in which life resides. It is the "physical basis of life." 

 Vegetable cells generally have cell walls of cellulose surrounding the 

 living protoplasm of the cell (protoplast). 



Cells divide to form tissues. 



Protoplasmic Cell Contents 



Protoplasm consists of four well-differentiated portions : 

 (a) Cytoplasm, or the foamy, often granular matrix of protoplasm 

 outside of the nucleus. 



Vacuole 



Passive bodies 

 (metaplasmor 

 paraplasm) 

 suspended in 

 the cyto- 

 plasmic mesh- 

 work 



Fig. I. — Diagram of a cell. 



{From Hegner's Zoology, after Wilson, published by the 

 Macmillan Co.) 



(b) Nucleus or Nuclearplasm, a denser region of protoplasm con- 

 taining chromatin, a substance staining heavily with certain basic dyes. 



(c) Nucleolus, a small body of dense protoplasm within the nucleus. 



(d) Plastids, composed of plastid plasm, small discoid bodies scat- 

 tered about in the cytoplasm. Sometimes, as in the cells of lower plants 

 like the Spirogyra, plastids are large and are then called chromatophores. 



