BOTANY. 315 



as they possess odor or not. 2. If the circumstances in which these 

 flowers accomplish the phenomena be identical, the proportion of car- 

 bonic acid increases with the elevation of the temperature. 3. Generally, 

 for flowers cut from the same plant and whose weight is equal, the 

 quantity of carbonic acid is rather more considerable when the appar- 

 atus in which the experiment is made is exposed to light than when in 

 extreme darkness : but in some cases there is no difference. 4. When 

 ordinary air is replaced by pure oxygen the differences become more 

 marked. 5. The flower beginning to develop disengages a little more 

 carbonic acid than that which has attained its complete development : 

 this may be due to a more energetic vital action. 6. Flowers left in 

 an inert gas, disengage small quantities of carbonic acid. 7. The ele- 

 ments which constitute the flower (the pistil and the stamens) in which 

 reside the greatest power of vitality, consume the largest quantity of 

 oxygen and give oft' the largest proportion of carbonic acid. 



Oases exhaled by Fruits. M. Cahours also reports to the Acade- 

 my, that he has found that the green parts of plants are not the only 

 structures which have the power of breathing. lie states that he finds 

 that apples, oranges, and citrons, placed under bell jars containing 

 oxygen, or this gas mixed with nitrogen, consumed oxygen, and 

 evolved carbonic acid, the proportions being greater in diffused light 

 than in darkness. Up to a certain point this takes place gradually, 

 but beyond this it increases to a considerable extent, .and the internal 

 surface of the pericarp exhibits certain alterations of structure. The 

 greater the temperature the larger will be the volume of carbonic acid 

 exhaled. Nearly the same amount of carbonic acid is evolved during 

 the two periods of approaching maturation and decay. But once the 

 latter stage has been arrived at, the quantity of exhaled carbonic acid 

 increases rapidly. The proportions of gases contained in the juices 

 were thus estimated : The juice having been expressed was placed in 

 vessels, and the gases expelled by ebullition. It was found in this way 

 that carbonic acid and nitrogen are present in various proportions, but 

 that none of the following exist in fruit juice : Oxygen, hydrogen, car- 

 bonic oxyd, carbureted hydrogen. When ripe fruit is enclosed in an 

 atmosphere of air, it absorbs hydrogen with great rapidity, and if it 

 is allowed to remain until it has become soft, it is found to contain a 

 large proportion of gas rich in carbonic acid. 



