296 NATURE STUDY AND AGRICULTURE 



Experiment. — Fill a box or dinner plate with soil and 

 sow some oats or wheat seeds. After the grains are 

 sprouted, cover one-half the plants with a box or tin can. 

 Give all the plants the same amount of water. After a 

 week compare the plants grown under cover with those 

 grown in the light. What do the former lack ? What is 

 your conclusion as to the ability of the plants to make 

 chlorophyll without light? Can the plant make starch 

 without chlorophyll? 



Experiment. — Cut two thin slices from the end of a 

 cork stopper. Place one slice on the upper surface of a 

 leaf of a vigorously growing geranium, or better, a nas- 

 turtium and the other slice directly beneath. Stick a 

 couple of pins through them to hold them on. Leave 

 them till the afternoon of the next day if the sun has been 

 shining. Now remove the leaf from the plant and the 

 piece of cork from the leaf. Boil the leaf in water for a few 

 minutes. Soak the leaf for several days in strong alcohol. 

 Change the alcohol until you are sure all the chlorophyll 

 is dissolved out. Rinse out the alcohol with plenty of 

 water, then place the leaf in iodine for fifteen or twenty 

 minutes. Rinse off with water. Does any part of the leaf 

 show the presence of starch? Is there any starch where 

 the leaf was covered from light with the slice of cork ? It is 

 a good thing to try several leaves at once. Some will 

 probably be much more successful than others. 



Without light, then, plants cannot make chlorophyll, 

 and without the chlorophyll no starch, protein, or other 

 product can be made by the protoplasm. The light then 

 is the power that runs the machinery, but the chlorophyll 

 is the connecting link between the power and the machine. 



