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J. W. SHIVE AND B. E. LIVINGSTON 



discussed, each series comprising, as has been stated, twelve 

 cultures in each of the five different exposures. During the prog- 

 ress of an experiment it sometimes happened that plants became 

 injured in other ways than by mere wilting, and in such cases the 

 cultures containing these plants were discarded from the group. 

 It also sometimes occurred that cultures supposed to have been 

 permanently wilted proved later (when tested in the moist 

 chamber, as above described) not yet to have attained this con- 

 dition; these were also omitted. Thus the results given below do 

 not account for all of the original quota of sixty cultures. Rel- 

 atively few are thus omitted, however. 



TABLE 1 



Characteristics of the soils used in wilting experiments 



Series I. Maize plants were used in this series, the plants 

 being four weeks old at the beginning of the experiment, which 

 was begun August 8, 8 a.m. The soil mixture contained three 

 volumes of sand and one volume of clay loam, with a moisture 

 holding power of 32.02 per cent. , of its dry weight. From the Briggs 

 and Shantz formula the calculated moisture residue at permanent 

 wilting is, for the soil, 3.80 per cent, of the dry weight. There were 

 three plants in each culture. The first permanent wilting occurred 

 in the chamber in the open, August 8, during the sixteenth hour; 

 i.e., between 3.00 and 4.00 p.m. Twelve cultures became per- 

 manently wilted during this hour and the average soil moisture 

 residue from these was 6.04 per cent. The average evaporation 

 rate for the two-hour period during which wilting occurred was 

 3 cc. Permanent wilting occurred in the glass box on August 9, in 



