The Boot and the Soil. 



67 



and add a little olive oil to form a film over the liquid 

 thus preventing it from absorbing more air. Then agi- 

 tate the refet of the water vigorously to impregnate it 

 again with oxygen, and pour some of this into the sec- 

 ond tumbler. Set both tumblers in a light, warm place. 

 In a few days roots will start freely from the slip in 

 the tumbler in which 

 the water has access 

 to the air, but not in 

 the other (Fig. 27). 

 If now the rooted 

 cutting is placed in 

 oil-covered water that 

 has been exhausted 

 of its oxygen by 

 boiling, the roots will 

 soon die. 



The copious for- 

 mation of root-hairs 

 (100) that reach out 

 into the moist atmos- 

 phere of the seed- 



FiG. 27: Slips of Tradescantia in water 

 tester (38), and that containing oxygen (left glass) and in 

 water containing no oxygen (right glass). 

 SO often fills the soil From nature. 



cavities with a delicate, cottony down, is further proof 

 that roots search for air as well as water. The total 

 absence of live rootlets in the puddled clods of badly- 

 tilled fields shows that roots will not penetrate soil from 

 which the air has been expelled by undue compression 

 while wet. Plants in over-watered greenhouse pots 



