202 



Journal of Agricultural Research 



Vol. XVI, No. 8 



CARBON DIOXID 



Perhaps the most natural assumption in regard to apple-scald is to 

 consider carbon dioxid as the responsible agent. The writers have made 

 numerous experiments looking to the establishment of this hypothesis, 

 but these have resulted in proof that carbon dioxid is not a causal 



agency in the produc- 

 tion of the disease. 

 The nature and results 

 of the experiments are 

 shown in figure 1 1 . 



The results give con- 

 clusive evidence that 

 an accumulation of 

 carbon dioxid is not 

 responsible for the 

 production of scald. 

 In 2 of the lo differ- 

 ent tests the amount 

 of scald was slightly 

 decreased with a de- 

 crease in amount of 

 carbon dioxid, but 

 with the other 8 it 

 was either unchanged 

 or decidedly increased. 

 The results as a whole 

 indicate that, while an 

 accumulation of the 

 gas may sometimes be 

 an accompaniment of 

 apple-scald, carbon 

 dioxid itself really tends to prevent rather than aggravate the develop- 

 ment of the disease. 



Fig. s. — Graphs showing the effects of temperature on apple-scald at the 

 end of 2, 3, 4, 5, 9, and ii weeks. The dotted graph shows the amount 

 of scald that was evident after removal from storage at the end of the 

 given week and holding the apples at 20° C. for 3 days. The apples 

 were of the same lot as those of figure 4 and were picked on the same 

 day, but were held in commercial cold storage from September 14 to 

 October 15, and were transferred to the storage boxes for the above 

 experiment on the latter date. The weeks of storage as given on the 

 graphs are counted from October 15, the time of starting the special 

 experiment. 



Tabi,E IV. — Effect of storing apples in carbon dioxid for short periods on development of 



scald 



Ex- 

 peri- 

 ment 

 No. 



Al. 

 A2. 

 Bi. 

 B2. 



Treatment. 



Apples in 100 per cent of carbon dioxid at 30° C. for 3 days, then at 15° 



in moist chamber for 8 weeks. 

 Apples in moist chamber at 15° continuously for the above-mentioned 



periods without carbon-dioxid treatment. 

 Apples in 100 per cent of carbon dioxid at 15° C. for 6 days, then in 



moist chamber at 15° for 11 weeks. 

 Same as Bi, but continuously in moist chamber without carbon-dioxid 



treatment. 



Percent- 

 age of 

 scald. 



O 

 o 



40 



