30 



BIOLOGY 



FlG. 9. A DIAGRAM OP AN IDEAL CELL 

 I, linin; 

 m, microsomata; 



as, centrosphere ; 

 ch, chroma tin; 

 cr, centrosome; 

 cw, cell wall; 

 cy> cytoplasm; 

 /, fibers; 

 ky, karyoplasm; 



nm, nuclear membrane; 

 n, nucleus; 

 no, nucleolus; 

 p, plastids; 

 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 RPIROGYRA 



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. 



