Academy of Sciences in Paris. 337 



abundant crops than from similar fields which had not been prepared 

 in the same manner. M. Dutrochet has not contented himself with 

 the mere relation of facts, but has, with great ingenuity, accounted for 

 them by tracing the fertilising qualities of silex to the manner in 

 which it renders the roots of the plants accessible to the air and 

 water, from which they derive their principal nourishment. The 

 reporter, in conclusion, submitted that the memoir deserved the high 

 approbation of the Academy an opinion which was unanimously 

 adopted. 



BOTANY. 



Respiration of Plants. On the llth July, M. Dutrochet read a 

 memoir on this subject. He commenced by referring to the experi- 

 ments of Bonnet and Adolphe Brogniart, from which it had been 

 ascertained that the lower surface of leaves contains a number of 

 aerial cavities, communicating with the external air of the openings 

 of the stomata, which, it was presumed, were instrumental to the re- 

 ception of the principles producing that elaboration of the sap in the 

 leaves which has induced some physiologists to consider leaves as 

 the lungs of plants. M. Dutrochet's object was to verify this suppo- 

 sition. Having observed that many leaves, particularly those of 

 leguminous plants, lost the whitish tint of their lower surface on being 

 plunged into water, he was induced to suppose that this pheno- 

 menon might be occasioned by the introduction of water into the 

 cavities previously occupied by air. To ascertain this, he put a bean- 

 leaf into a glass vessel filled with water, and, having completely 

 submerged the leaf, he placed the vessel under the receiver of an air- 

 pump. As the air became exhausted, bubbles of air were seen to 

 issue from the leaf, particularly from every point of the lower sur- 

 face. After the lapse of half an hour the air was re-admitted, and 

 the lower surface of the leaf instantly lost the whitish tint, which it 

 had preserved until that moment. On taking the leaf out of the 

 water, he found that the lower surface had, in fact, become precisely 

 of the same colour as the upper surface ; thus proving that the white 

 tint of the lower surface of the leaf is entirely produced by the pre- 

 sence of air. Sometimes leaves appear to have white spots on the 

 surface : these are proved also to result from the same cause, and 

 disappear as soon as the air is removed by the action of an air-pump. 

 The introduction of the air into the parenchyma takes place through 

 the openings of the stomata, which does not prevent those openings 

 serving at the same time for the transpiration of the leaves and the 

 absorption of atmospheric air. M. Dutrochet then ascertained, not 

 only that there is an immediate and easy communication between 

 these aerial cavities by means of all those parts of the leaf which are 

 not separated by thick nerves, but that the ae'rial cavities of leaves 

 form part of a pneumatic system, extending throughout the whole 

 plant. To prove the direct correspondence between the aerial cavi- 



