30 STUDIES ON FEUIT RESPIRATION. 



The air entering each jar was purified by passing it through a 

 glass tube, 35 cm long and 5 cm in diameter, filled with soda lime. 

 It was then drawn through a bottle containing baryta water and into 

 the jar. The tube entering the container terminated near its cover, 

 while the exit tube reached nearly to the bottom. The air drawn 

 from the jars passed through a Reiset absorption apparatus, then 

 through a wash bottle containing baryta water and to a suction pump. 

 A failure of the soda lime to remove carbon dioxid from the entering 

 air would, of course, be shown by the appearance of turbidity in the 

 first bottle of baryta water, while the last bottle of baryta water 

 would reveal a failure of the Reiset tube to absorb the carbon dioxid 

 completely. In three experiments, the results of which are detailed 

 on page 32, these bottles indicated that the air was properly purified 

 and that there was a complete absorption in the Reiset tubes of 

 the carbon dioxid formed by the fruit. 



The air was aspirated through each apparatus at the rate of about 

 2 liters per hour and was conveyed in glass or copper tubes, avoiding 

 use of rubber tubing as far as practicable on account of the recog- 

 nized selective absorption of carbon dioxid by rubber and because 

 of the marked tendency of much of the rubber tubing on the market 

 to develop minute cracks when exposed to the weather. 



The carbon dioxid was estimated by the method employed in t-he 

 study of the effect of temperature on fruit respiration. (See page 11.) 



As a good many difficulties were encountered during the progress 

 of the work, only three experiments were completed. It was hard 

 to make the joint air-tight between the branch and the jar, and the 

 percolating jars cracked at very inopportune times on account of 

 the warping of the covers. One of the jars cracked during experi- 

 ment 1. In experiment 2, as no other percolating jar was available, 

 a tubulated desiccator was substituted, in which the picked fruit was 

 held. In experiment 3 a large museum jar with a cover made of 

 hard rubber was substituted for the percolating jar for fruit attached 

 to the tree. It was planned to support both jars under the tree on 

 tripods, but these proved not to be sufficiently stable, and the jars 

 were therefore attached by means of universal clamps to half -inch 

 vertical iron rods, the sharpened ends of which were driven irrmiy into 

 the ground. Only sound normal fruits from the same portion of the 

 same tree were selected. The foliage was carefully trimmed away 

 from the group of fruits selected for inclosure in the jar while attached 

 to the tree. The detached fruit was weighed at the beginning of 

 each experiment and the attached fruit at its conclusion. 



