64 AERATION AND AIR-CONTENT. 



acid as well. They cited the work of Aso (1906) which showed that 

 acetic and formic acids, even in greatly diluted solutions, exerted an 

 unfavorable influence upon lower as well as higher plants. More- 

 over, the salts of both of these acids in similar concentrations were 

 poisonous to plant organs. Aso explained this poisonous effect of 

 the salts of formic and acetic acids as probably due to hydrolytic 

 dissociation in the hving cell of these salts into acids and bases, 

 by which the base was absorbed by the proteids, while the acid was 

 released and acted unfavorably upon the living protoplasm. Acid 

 aldehyde and acetone were always found alongside of acetic and 

 formic acid, all of which have been shown by Aso to be poisonous. 



Babcock (1912 : 150) confirmed the results of earlier investigators 

 upon the behavior of apples and pears under anaerobic conditions, 

 and noted that there was practically no difference in the final results 

 when hydrogen, nitrogen, carbon dioxid, or the residual gas of respi- 

 ration was employed, or the fruits immersed in cotton-seed oil. 

 Succulent tissues of all kinds behaved in similar fashion in the ab- 

 sence of oxygen, but in young tissues the production of acids was 

 found to be more rapid and the life of the cells short. 



Hill (1913) reached the following conclusions respecting the anae- 

 robic respiration of fruits: The anaerobic production of CO2 by 

 ripe cherries, blackberries, and grapes is as rapid as the aerobic 

 production for a considerable length of time. Ripe fruits that spoil 

 quickly, such as cherries, have a higher respiratory rate than those 

 that do not spoil so quickly, such as grapes. This is due possibly 

 to a higher enzyme-content. Fruit tissues that respire as actively 

 anaerobically as aerobically seem to be those that have finished 

 their growth and are ripe. Growing tissues, such as green peaches 

 and germinating wheat, respire more than twice as rapidly aerobi- 

 cally as anaerobically. The activity of the protoplasm would 

 seem to be connected with the more direct use of oxygen in the 

 production of CO2. If growing tissues, such as green peaches, are 

 placed in an oxygen-free gas for a few days and then brought back 

 into air, the rate of production of CO2 does not entirely return to 

 the normal. This would indicate a permanent injury to the proto- 

 plasm or to some of the enzymes, due to insufficient oxygen. 

 Ripe apples lose their color, texture, and flavor, and take on the 

 quahties of half-baked apples, by being kept for a sufficient length 

 of time in oxygen-free gases (N, H). This emphasizes the need of 

 good aeration for apples. The softening of peaches seems to be de- 

 creased greatly by CO2 and to a considerable extent by hydrogen 

 and nitrogen. Peaches become brownish and acquire a very bad 

 flavor when oxygen is withheld from them. ''Ice-scald" seems to 

 be an injury due to insufficient oxygen and to an accumulation of 

 CO2 within the paper wrappers in which peaches are so often 

 shipped. With good ventilation in conjunction with good refrigera- 



