30 



BIOLOGY 



as cw 



p 



f 



FlG. 9. A DIAGRAM OF AN IDEAL, CELL 



as, centrosphere ; Z, linin; 



cA, chroma tin; TO, microsomata; 



cr, centrosome; WTO, nuclear membrane; 



cw>, cell wall; n, nucleus; 



cy, cytoplasm; no, nucleolus; 



/, fibers; p, plastids; 



karyoplasm; 



v, vacuole. 



stance) has been given. This material 

 within the cell wall, or lie in the form 



of the ostrich, which is 

 really a single cell. As 

 a rule, however, cells 

 are microscopic in size. 

 Shape. A cell is usu- 

 ally more or less spher- 

 ical (Fig. 9), although 

 it may be distorted by 

 pressure or irregular 

 growth. 



CELL SUBSTANCE OR 

 PROTOPLASM 



The material which 

 composes the active 

 part of the cell appears 

 like a mass of more or 

 less transparent jelly to 

 which the name pro- 

 toplasm (Gr. protos = 

 first + plasma = sub- 

 may fill the entire space 

 of a thin layer next to 



FIG. 10. CELL OF SPIROGYRA 



cl, cell chlorophyll; cs, cell sap; cw, cell wall; n, nucleus; p, protoplasm. 



the cell wall, the rest of the space being filled by a watery 

 liquid; Fig. 10. 



