Nutrition. 87 



time to time. Can the seedling in the darkness live as long as 

 the one in light? The plants in darkness are said to be etio- 

 lated, and have not formed chlorophyl. The lack of chloro- 

 phyl, and of its action in the presence of sunlight, results in the 

 starvation of the etiolated specimen. 



87. Growth of plants in air free from carbon 

 dioxide. — Chlorophyl is active in the use of the carbon diox- 

 ide of the air in the formation of foods in the leaf. It will be 

 profitable to observe the behavior of the plant when placed in 

 a condition in which it may not have access to carbon dioxide. 

 To accomplish this, make the following preparation : grow 

 seedlings of corn or sunflower in two small pots, and provide 

 two large bell jars with a tubulure at the top or on the sides. 

 Set the pots containing the seedlings on separate sheets of 

 glass. One is to be used as a test, and the other as a control. 

 A shallow dish containing several sticks or fragments of potas- 

 sium or sodium hydrate should be placed under the bell jar with 

 the test object. Fit a perforated rubber or cork stopper tightly 

 to the opening in the bell jar, and insert a drying tube filled 

 with sodium hydrate in the perforation. Omit hydrate from 

 control experiment. The hydrate in the bell jar will take up 

 all the carbon dioxide in the chamber, and all the air enter- 

 ing through the drying tube is similiarly acted upon. Renew 

 the preparation at least once a week. After a week or two, 

 note action of plant in an atmosphere free from carbon dioxide, 

 and compare with the control plant under a second bell jar, in 

 which no sodium hydrate has been placed. 



It will be necessary to shield the plants from the direct rays 

 of the sun, since the temperature in the confined chambers, 

 which are not well ventilated, would be raised above the normal. 



88. Properties of chlorophyl. — Place 100 grams of 

 freshly chopped leaves in a flask, and cover with water. Test 

 with litmus paper, and, if acid, add enough sodium carbonate to 

 neutralize. Boil for half an hour. Pour off the water, and wash 



