T. C. Broyer 237 



levels of oxygen were made. The growth of plants and potassium 

 accumulation by roots of three species are reported in Table X (88). 

 This shows the variable effect for these species, of oxygen supply to 

 roots from its bathing medium. The inference, which is borne out by 

 evidence of others (14, 95), is that the requirements for oxygen in 



TABLE X 



Fresh Weight and K Concentration of Sap of Plants Grown outdoors 6 Weeks 



in Culture Solution with Gas Exposure. — Vlamis and Davis (88) 



Plant 



Root 

 Treatment 



Shoots 



Fresh 

 weight 



Roots 



Fresh 

 weight 



K 



cone. 



Note: Methane gas contained less than 0.02 per cent of oxygen. 



some species is met by a transport of this gas from the shoots to the 

 roots. This implies a difference in anatomy, or some oxygen transport 

 process within the various types of plants. Anatomical studies showing 

 the development of air passages favor the former assumption (21). The 

 data of Vlamis suggest a most favorable position for rice, an unfavora- 

 ble position for tomato, and an intermediate position for barley, in this 

 regard. His data, in accord with others referred to earlier, show the 

 very harmful indirect and direct effects of relatively high concentra- 

 tions of carbon dioxide in the environment of roots. 



Although transpiration is considered unnecessary and certainly not 

 directly essential to accumulation of inorganic solute by the roots of 



