II. EFFECT OF PICKING ON THE RATE OF EVOLUTION OF 

 CARBON DIOXID BY PEACHES. 



In the discussion of the rate of the formation of carbon dioxid by 

 fruits Mr. Taylor suggested that experiments be made on peaches 

 in the orchard to determine whether or not they received a stimulus 

 on picking which would be made known by an increase in the rate 

 of evolution of carbon dioxid; by measuring the rate of change an 

 idea of the magnitude of the stimulus to the life processes might be 

 obtained. Field studies were accordingly made and facilities were 

 provided at the Arlington Experiment Farm, where valuable coop- 

 eration was given in the conduct of the investigation. So far as 

 known no data are on record of similar studies. 



APPARATUS AND METHOD EMPLOYED. 



Pure air was run through a jar containing peaches attached to the 

 trees and the amount of carbon dioxid given off during a known 

 period contrasted with that formed by peaches at the same stage of 

 ripeness after picking. 



The jar which contained the attached fruit was provided with a 

 split cover which could be fastened together air-tight by means of 

 long screws after it had been taken apart to admit the branch. The 

 joint between the branch and the cover and the joint of the cover 

 were made air-tight either by use of grafting wax or a specially 

 prepared rubber compound used by electricians. The large perco- 

 lating jars used in experiments 1 and 2 were fitted with brass collars 

 provided with threaded bolts and thumbscrews by which the covers 

 of paraffined hard maple were brought tightly against a rubber 

 gasket at the edge of the jar. 1 



The jars were screened from direct sunlight to avoid the rapid 

 rise in temperature due to the "greenhouse" effect; and in order to 

 keep both lots at the same temperature because of its marked effect 

 on the rate of respiration, they were kept near each other under the 

 tree at about the same height. 



1 L. J. Briggs, Bureau of Plant Industry, assisted in designing these covers and having them made. 



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