LEAVES I I 3 



Experiment. Take leaves from a plant of silver- 

 leaf geranium growing in the sunlight. If this 

 plant cannot be had, the leaves from some other 

 variegated white and green leaved plant will do. 

 Boil these leaves, treat with alcohol, wash and test 

 with iodine (Fig. 64). Starch will be found in the 

 leaf wherever there was green coloring matter in 

 it, while the parts that were white will show no 

 starch. The green coloring matter seems to have 

 something to do with the starch making, in fact 

 starch is manufactured only where it is present. 

 This coloring matter is called chlorophyl or leaf 

 green. 



We are told by the chemists that this starch is 

 made from carbon and water. There exists in the 

 air a gas called carbonic acid gas ; this gas is com- 

 posed of carbon and oxygen. It is breathed out 

 of the lungs of animals and is produced by the burn- 

 ing and decay of organic matter. The under side 

 of the leaf contains hundreds of little pores or 

 mouths called stomata. This gas mixed with air 

 enters these mouths. The green part of the leaf 

 aided by the sun takes hold of the gas and separates 

 the carbon from the oxygen. The oxygen is allowed 

 to go free, but the carbon is made to unite with 

 water and form starch. 



Experiment. The escape of this oxygen gas 

 may be seen by taking some water weed from either 

 fresh or salt water and placing it in a glass jar of 

 the kind of water from which it came, then set the 

 jar in the sunlight. After a time bubbles of gas 

 8 



