86 CARNEGIE INSTITUTION OF WASHINGTON. 



Relation between Atmospheric Conditions and Soil Moisture Content at 

 Permanent Wilting of Plants, by B. E. Livingston and J. W. Shive. 



The study of this relation, already advanced by the work, at the 

 Desert Laboraton^ of Dr. W. H. Brown (1909) and Dr. J. S. Caldwell 

 (1910), was carried farther, also at the Desert Laboratorj^ in the 

 summer of 1913, by Mr. Shive and Professor Livingston. The results 

 showed, for several soil mixtures and several plant forms, that the 

 moisture-content of the soil at permanent wilting of the plants increased 

 approximately 0.5 per cent (on basis of dry-soil weight) for each 

 doubling of the atmospheric evaporating power. 



The Water-attracting Power of the Soil, as measured by the Rate of Loss 

 from the Auto-irrigator, by B. E. Livingston and L. A. Hawkins. 



The auto-irrigator is essentially like a porous-cup atmometer, the cup 

 buried in the soil instead of being exposed to the air. Dr. L. A. Haw- 

 kins, of the U. S. Department of Agriculture, working with Professor 

 Livingston at the Laboratory of Plant Physiology of the Johns Hopkins 

 University, carried out a series of measurements upon potted plants 

 irrigated automatically with this device. In such cultures the rate of 

 water-loss from the irrigator is highest somewhat later in the day than 

 occurs the maximum in the transpiration rate. The rate of loss from 

 the irrigator then falls slowly, reaching its minimum in the early morn- 

 ing. It appears that this rate may be valuable in the dynamic study 

 of soil-moisture conditions. 



The Water-supplying Power of the Soil, by B. E. Livingston and 



H. E. Pulling. 



As mentioned in the preceding report, Mr. H. E. Pulling, fellow in 

 botany in the University of Wisconsin, working at the Desert Labora- 

 tory during the summer of 1913, measured the water-supplying power 

 of several soil mixtures by means of cane-sugar osmometers with collo- 

 dion membranes. This method, together with other possible methods 

 for measuring the water-suppljang power of the soil, promises to open the 

 field of water relations between plant and soil, so that these may be 

 quantitatively studied. Mr. Pulling is continuing these investigations 

 at the University of Wisconsin. 



The Transpiring Power of Plant Foliage, as measured by the Method of 

 Standardized Hygrometric Paper, by B. E. Livingston and A. L. Bakke. 



]\Ir. A. L. Bakke, instructor in plant physiology in Iowa State Col- 

 lege, working with B. E. Livingston at the Desert Laboratorj^ during 

 the summer of 1913, obtained comparative measurements of this im- 

 portant and apparently characteristic internal feature for a large num- 



