PRELIMINARY EXERCISES. 5 



obtained. Examine these cells (l.p.) and ob- 

 serve, — 



(a) the shape of each cell ; 



(6) the cell wall, a membrane surrounding the cell ; 

 (This is not always easily seen.) 



(c) the cytoplasm, the portion of the cell within the 



cell wall ; 



(d) the nucleus, a small body embedded in the cyto- 



plasm. The cytoplasm and nucleus together 

 are called protoplasm (living substance). 



2. Select a typical cell and make a drawing, 2 centi- 



meters in diameter (2 cm.), to illustrate the points 

 just observed. 



3. Make a clay model to show your idea of the shape 



of a typical cell. 



. Associated Cells, usually called "tissue." 



Ascertain as before whence your material was ob- 

 tained. 



1. Identify cytoplasm, cell wall and nucleus. 



2. Explain the difference in shape between an inde- 



pendent cell and a single cell in a tissue. 



3. Make a drawing of six adjoining cells, making each 



cell 2 cm. in its greater diameter. 



