BIOLOGY OF HIGHER SEED PLANTS 31 



d. Composition of cJiloroplastids. Select shoots of Elodea 

 which have been previously boiled to kill the plas- 

 tids. Place one or more shoots in a test tube in 

 ninety-five per cent alcohol and observe frequently. 

 Does the alcohol change color ? "Why ? Allow these 

 test tubes to stand until the next exercise. Examine 

 the alcohol, the plants, and the plastids. Do the 

 plants appear to be somewhat bleached ? Explain. 

 What are the parts of a chloroplastid ? Answer the 

 above questions in your notes, indicating the form, 

 parts, and function of chloroplastids in cells of Elodea. 



CHROMOPLASTIDS 



1. Examine chromoplastids in the cells of flowers (for ex- 



ample, Nasturtium) and fruits (for example, tomato and 

 bittersweet berries). Draw the chromoplastids examined. 



2. See the text discussion of the structure and functions of 



plastids. 



B. CELL STRUCTURE AND GROWTH 

 GROWTH 



1. Growth of root tips in living roots of corn or beans. 



a. Observe growing root tips which have been previously 



marked with uniform millimeter spacings and then 

 allowed to grow for twenty-four hours or more. In 

 what part of the root tip has growth taken place ? 

 How long is the growing zone as indicated by the 

 millimeter spaces ? Does the root grow at the 

 very tip ? 



b. Draw a root which has grown in the manner indicated 



above. Indicate the length of the millimeter spaces 



