13. SEEDS CAN NOT GERMINATE WITHOUT 



AIR. 



Illustrative material: Two shallow dishes or saucers, two 

 tumblers, and a few grains of wheat. 



Half fill two wide-mouthed bottles or two jelly cups with soil 

 that is wet enough to be easily worked up in the hands like soft 

 putty. Pack the soil in one of the dishes until the air is well 

 pressed out of it, adding enough soil to make the dish half full 

 when packed. Leave the soil loose in the other dish. Put a 

 few wheat grains on the surface of the soil in each dish and 

 cover these to the depth of about a quarter of an inch in the 

 dish with the soil unpacked and with packed soil in the other 

 dish. Close both dishes and put them in a warm place. 



Air Necessary for Germination Figure 28 shows 

 two shallow dishes, in each of which kernels of wheat 



were placed. Enough 

 water was then added 

 to the right-hand dish 

 to cover the kernels to 

 about half their depth, 

 and to the. left-hand 

 dish to cover them to 

 twice their depth. The 

 Vtf . pa . c dishes were then set in 



riG. 28. Effect of air on seeds. 



a warm room and cov- 

 ered with tumblers to prevent evaporation of the water. 

 After two days, the kernels in the right-hand dish had 

 germinated, while none of those in the left-hand dish 

 had done so. Why did not the kernels in the left-hand 



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