208 FIRST TEAR SCIENCE 



another similar corked empty bottle beside it. Allow the bottles to 

 stand for several days until the peas have sprouted. Remove the cork 

 from the bottle containing the peas and insert a burning splinter. Do 

 the same to the empty bottle. Why does not the splinter burn as well 

 in each? If on being placed in either bottle the splinter is smothered 

 out, it shows the presence of carbon dioxide. 



Experiment 109. Fill two 8-ounce wide-mouth bottles each about 

 one third full of coarse sawdust and fill the remaining part with peas 

 which have been soaked for a day. Pour in sufficient water to cover the 

 sawdust. Cork one of the bottles tightly, leaving the other open. 

 Put the two bottles in a warm sunny place. Whenever necessary, 

 pour on sufficient water to keep the sawdust in the open bottle wet. 

 In which bottle do the seeds sprout the better ? Does air appear to 

 be necessary for the growth of seeds ? As determined by the previous 

 experiment, what part of the air is used ? 



We found in Experiment 107 that if the cotyledons 

 were cut off before the sprout had become sufficiently 

 mature, it could not continue its growth. In Experiment 

 108 we found* that the sprouting seeds took up oxygen 

 from the air and gave out carbon dioxide just as animals 

 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 109 that the seeds could riot sprout well unless suffi- 

 cient air was supplied. That was because there was not 

 enough oxygen supplied to furnish the necessary energy. 



Experiment 110. 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 110 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. 



