PROBLEMS 



25 



V. Turn on the high power. Again draw the letter, or as much as you 

 can see of it, as large as it appears. Measure your drawing with your- ruler 

 and see how many times the high power appears to magnify the letter. 



VI. Have your teacher tell you how much the microscope really enlarges 

 the object with low and high power. Cmdion. Always find your object with 

 the low-power objective, then turn on 

 the high power. If you lose your high- 

 power focus, go back to low power and 

 refocus. 



Problem. How do onion cells ap- 

 pear when viewed through the micro- 

 scope f 



Cut an onion into halves or quarters. 

 Peel off one of the scalelike leaves. 

 By means of a pair of forceps or knife 

 strip the thin tissue from the inside of 

 the scale. Mount a part of it on a 

 glass slide in a drop of water and cover 

 with a cover glass. Be sure to flatten 

 your specimen before covering it. View 

 the material under the microscope. 

 Then remove cover glass, and stain 

 the material by adding a small drop of 

 dilute iodine solution. Again cover. Ob- 

 serve wdth low power, then high power. 



I. The little divisions that make up 

 the onion membrane are called cells. 



A. The boundary of each cell is 



the cell ivall. 



The cells of the onion tissue often show 



B. Describe the color and shape the heavy, woody walls and the large vacuoles 

 of these cells ^ *^^* ^'■^ characteristic of most plant cells. 



II. Observe the position of the granular and clear areas. The granular 

 areas make up the living part of the cell and are composed of a material called 

 cytoplasm. The clear areas are the vacuoles or fluid-filled spaces in the cytoplasm. 



III. Find a small dense area somewhere in the cytoplasm. This is the nucleus. 

 A. Each nucleus has two disklike structures called nucleoli. Try to 



identifv a nucleolus in a nucleus. 



WH. FITZ. AD. BIO. — 3 



