396 LIFE ON THE EARTH 



do. Energy was needed and this energy was obtained by 

 combining the carbon in the seed with the oxygen in the 

 air, as it is when wood is burned. We found in Experi- 

 ment 129 that the seeds could not sprout well unless suffi- 

 cient air was supplied. That was because there was not 

 enough oxygen supplied to furnish the necessary energy. 



Experiment 130. Place several sprouted seeds in each of two 

 tumblers nearly filled with damp sawdust. Put these tumblers 

 side by side in a warm, light place. Cover one of the tumblers 

 with a box painted black so as to exclude the light. In which do 

 the seeds grow the better? 



After the seeds were sprouted and had begun to pre- 

 pare their own food, it was found in Experiment 130 that 

 they were not able to do this unless exposed to the light 

 of the sun. The parent plant had stored, in a latent form 

 in the seed, energy which it had received from the sun. 

 This potential energy the sprout was able to change into 

 the kinetic form by the aid of oxygen, and to use in the 

 work of growing. After this latent energy had been ex- 

 pended, it had to fall back upon the direct energy of the 

 sun which came to it in the form of sunlight. 



Dependent Plants. Experiment 131. Expose a piece of 

 moist bread to the air for a short time and then put it into a covered 

 dish so as to retain the moisture. Does any change take place in 

 the bread ? Examine with a magnifying glass the mold which ap- 

 pears. 



Experiment 132. (1) Bruise a sound apple and place the bruised 

 part in contact with a thoroughly rotten apple. Wrap the two up 

 together in a wet cloth and put in a fruit jar. Seal the jar to prevent 

 the water from evaporating. (2) Plunge a pin repeatedly first 

 into a rotten apple and then into a sound one. Wrap the sound 

 apple in a wet cloth and seal in a fruit jar. (3) Place a lemon 

 which has developed a green, spongy, rotten place in it in contact 



