46 



WHAT IS BEING ALIVE? 



They both respond to (4), use (5) to grow or release 



(6), and respire. Nutrition is the process by which living 



things (8), (9), (10) and (11) food. 



jauc)eu5 





vacuole 



PROBLEM III. WHAT ARE CELLS AND HOW DO THEY 

 PRODUCE OTHERS? 



Laboratory Exercise. Put a drop of impure water on a slide. Cover 

 with a cover slide and observe it under a compound microscope. Adjust 

 the lenses until the particles in the water can be plainly seen. 



Now scrape, with a sterilized toothpick, the inside of the cheek. Place 

 a small bit of the material in a drop of pure water on a glass slide and 



stain it with a small drop of 

 diluted fountain pen ink or 

 methylene blue. Notice the 

 irregular blue structures or 

 cells. Find a deeper blue body 

 inside the cell. This is the 

 n ucleus. The outer faint blue 

 line marking the edge of the 

 cell is the cell membrane. 



Peel the skin from one of 

 the fleshy leaves forming an 

 onion bulb, mount a small bit 

 of it in water to which is 

 added a drop of dilute tinc- 

 ture of iodine. Examine it 

 under a microscope. Note 

 the cells. Plant cells differ 

 Chloroplast from animal cells in that they 

 have a delicate wood icall out- 

 side the membrane. Draw 

 two or three animal and plant 

 cells in your notebook . Make 

 each cell at least one inch in 

 diameter. Label all parts. 



An examination of the delicate leaves of the Elodea, a water 

 plant used in aquariums, shows cells with many large spaces or 

 vacuoles, which are filled with a non-living fluid instead of proto- 

 plasm. Forming a part of the protoplasm are many small ovoid 

 bodies, most of which are green in color. These are the chloroplasts 

 (klo'rfi-plasts) or chlorophyll (klo'rfi-fil) bodies (Gr. chloros, green ; 

 phyllon, leaf). We shall see later that they are of the utmost im- 

 portance to each one of us, as it is by means of the action of the sun 

 upon them that food is manufactured in the green parts of plants. 



-ytoptem 



What are the characteristics of a plant cell? 

 does Elodea differ from animal cells? 



How 



