Mar. 18, 1918 Respiration of Stored Wheat 689 



Calcium-chlorid towers were used as respiration chambers. Paraffined 

 wire netting was fitted into the constriction near the base, and on this 

 the grain rested. Rubber connections were made as short as possible, 

 and all stoppers and tubing were thoroughly paraffined to prevent 

 selective absorption of carbon dioxid. In all instances where the same 

 lot of grain was worked with at different moisture contents, the several 

 portions were brought to approximately the desired percentage of 

 moisture by adding water from a burette, at the same time stirring 

 thoroughly. The samples were allowed to stand in sealed jars for three 

 days, in order to insure uniform distribution of the water through the 

 kernels. It had been found by determining the rate of swelling of the 

 kernels that they reached their maximum size in considerably less than 

 three days, and from this it was concluded that the moisture distribution 

 would be complete in the 3-day interval. When the grain was ready 

 to work with, a weighed quantity v^^as sealed into the tower. Samples 

 were taken at this time for the determination of moisture. The amount 

 of grain placed in the tower varied with the moisture content, about 500 

 gm. being employed in the case of the lower moisture limits, while 

 about 300 gm. were used when the percentage of moisture exceeded 

 15.5 per cent. In this manner convenient and accurately determinable 

 quantities of carbon dioxid were obtained. After sealing the grain into 

 the glass cylinders, the air was removed and replaced by carbon-dioxid- 

 free air. The towers were then placed in the thermostat, which, except 

 when temperature was the variable, was maintained at 37.8° C. (100° F.). 



The period of incubation was fixed at four days, the exact number 

 of hours being noted at the time of removing the respiration chambers 

 from the thermostat. The accumulated carbon dioxid v/as then re- 

 moved through the tubulure at the bottom of the tower, carbon-dioxid- 

 free air being simultaneously admitted through the top. The carbon 

 dioxid was absorbed in N/4 barium hydroxid [Ba(0H)2] solution in 

 the special absorption tower, as described by Gurjar in the above- 

 mentioned paper. The respiration data given in the tables are stated 

 in terms of milligrams of carbon dioxid respired per 24 hours by each 

 100 gm. of dry matter. 



RELATION OF THE MOISTURE CONTENT OF WHEAT TO THE RATE OF 



RESPIRATION 



The observation of Bonnier and Mangin {1885) that respiration of 

 living plants varies directly with the humidity of the air might be 

 interpreted to mean that the moisture content of the tissues increased 

 in a humid atmosphere. This increase in turn may have occasioned 

 the rise in the rate of respiration. Maquenne {1900) concluded that 

 a reduction in the moisture content of seeds is accompanied by a reduc- 

 tion in the rate of respiration, and Lund (1894) discovered that the 

 desiccation of roots and tubers reduced their rate of respiration. 



