24 Professor Macaire on the 



Borbed during the night, and they leave no trace of this acid 

 in their atmosphere. Fruits detached from the plant likewise 

 add, during the day, oxygen to the air in which they are plunged, 

 even although that air do not contain carbonic acid. If their 

 vegetation is very weak and languishing, they vitiate the air 

 in which they are enclosed, but less in the sun than in the 

 shade. 



Green fruits, detached from the plant and exposed to the 

 successive action of nights and days, produce little or no alter- 

 ation on the purity or volume of the air in which they are 

 placed. The little alteration actually observed arises more 

 particularly from the change which takes place in their com- 

 position when they advance to maturity. Thus the green 

 grapes appear to assimilate a portion of the oxygen of the car- 

 bonic acid which they form in the air where they vegetate 

 night and day ; while grapes almost ripe emit wholly in their 

 atmosphere, during the day, the oxygen of the acid they have 

 produced during the night. If this result, which, though con- 

 stant, is very inconsiderable, be well established, it will follow 

 from it that the acidity of the verjuice tends to fix the oxygen, 

 and that the fruit passes from the acid state to the saccharine, 

 when it can derive nothing more than the carbon in the car- 

 bonic acid of the air. 



Green fruits decompose, wholly or in part, not only the car- 

 bonic acid they produce during the night, but also that which 

 may be added artificially to their atmosphere. This power be- 

 comes weaker as they approach to maturity. 



They likewise appropriate, in their vegetation, the oxygen 

 and hydrogen of water, making the latter to lose its liquid state. 



Properly to observe these results, it is necessary that the 

 fruits be placed in a sufficient volume of air, equal to thirty or 

 forty times their own volume, and it is requisite to prevent the 

 too powerful action of the sun. If these precautions are ne- 

 glected, it will be found that fruits vitiate the air, even in the 

 sun, by forming carbonic acid with the ambient oxygen ; and 

 it is from want of caution in this respect that M. Berard was 

 led to suppose that this formation of carbonic acid was the con- 

 dition necessary for ripening fruits. 



It was interesting, in an agricultural point of view, to know 



