182 Deficient Soil Oxygen [380 



Obviously, the absorbing powers of these plants were inade- 

 quate to supply water as rapidly as it was lost by transpira- 

 tion during the hours when this loss was most rapid; the 

 inadequacy was within the plant, an internal condition. It 

 is suggested that the power of stem and petioles to conduct 

 water from roots to leaves is here also inadequate, but on 

 this point further experimentation will be required. 



One definite advance in our knowledge of the water rela- 

 tions of plants is made by the data here considered; it may 

 now be clearly stated that none of these three stages or de- 

 grees of incipient drying need necessarily be related to soil-, 

 moisture conditions at all. That they may sometimes be so 

 related, when the soil about the root system fails to supply 

 moisture to the root surfaces as rapidly as these are able 

 to absorb it, is sufficiently clear on a priori grounds. 



THE EFFECT OF DEFICIENT SOIL OXYGEN ON THE 

 ROOTS OF HIGHER PLANTS 



By B. E. LIVINGSTON AND E. E. FREE 



During the last three years experiments have been in 

 progress in the Laboratory of Plant Physiology on the oxy- 

 gen requirement of the root systems of higher plants. A 

 technique has been devised by which the root system, con- 

 tained in normal soil, can be sealed off from the air and th- 

 soil atmosphere controlled in composition as may be desirecL 

 The aerial portions of the plants project into the atmosphere 

 of the greenhouse. Water is supplied to the roots by means 

 of the Livingston auto-irrigator. 1 It has been found that 



1 Livingston, B. E., " A method for controlling plant moisture." 

 Plant World 1 1 : 39-40. 1908. Hawkins, Lon A., " The porous clay 

 cup for the automatic watering of plants." Plant World 13: 220-227. 

 1910. Livingston, B. E., and Hawkins, Lon A., "The water-relation 

 between plant and soil." Carnegie Inst. Wash. Pub. 204: 5-48. 1915. 



