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 5 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 sodl- 
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. Livrneston anp E. BE. 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 desired. 
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.t It has been found that 
* Livingston, B. E., “A method for controlling plant moisture.” 
Plant World (1: 39-40. 1908. Hawkins, Lon A., “The porous clay 
cup for the automatic watering of plants.” Plant World [3: 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. 
