TEMPERATURE FOR GROWING SEEDS 121 



An oversupply of water may prevent growth of seeds almost as 

 effectually as no water at all. In general the amount most favor- 

 able for germination is a moderate supply. Seeds rapidly lose 

 their vitality if kept in a very moist atmosphere, especially if the 

 moist air is hot. If seeds are given too much water they drown. 



Demonstration 5. To show the best temperature for germinating 

 peas. 



Materials. Soaked peas, sawdust, boxes. 



Method. Plant twenty soaked peas in each of three boxes containing 

 moist sawdust. Put one box in a place where the temperature is 

 about 150° F., another where the temperature is about 70° F., and the 

 third where the temperature is about 40° F. Give to all the same con- 

 ditions of air, light, and moisture. Observe them for four days. 

 Tabulate the daily observations. 



Conclusion. State what temperature seems best for germinating 

 peas. Give reasons. 



What is the best temperature for germinating seeds? Here 

 again our experiment answers the question only for the seed with 

 which we are working. Peas germinate best at one temperature, 

 corn another, wheat still another — or more properly, each variety 

 of a seed has a certain temperature (called its optimum) at which 

 it germinates best. It is this fact that makes possible the earlier 

 germination of some garden seeds. 



Demonstration 6. To show that air is necessary for germinating 

 peas. 



Materials. Soaked peas, bottles, sawdust. 



Method. Place an equal amount of moist sawdust in the bottom of 

 two bottles. Fill one bottle full of peas and close it securely with a 

 stopper. Put about twenty peas in the bottom of the other bottle. 

 Examine the bottles daily for four days. 



Conclusion. In which bottle did germination take place ? Why? 



Why is air necessary for germination ? All living things respire 

 or use oxygen in order to release energy and a seed is no exception 

 to the general rule. Without an ample supply of oxygen it 

 cannot release from its food supply the energy necessary for its 

 growth. Hence a constant supply of fresh air is an important 

 factor in the germination of seeds. If the seeds are planted in the 

 ground it is necessary for the soil to be sufficiently loose so that 

 air can penetrate it. 



