46 



is thus assimilated by the leaves, and would 

 be sufficient for the requirements of the plant, 

 yet it is absolutely necessary for the well-being of 

 our cultivated plants that it should likewise be pre- 

 sent in the soil, where it serves to bring the alkaline 

 earths and insoluble phosphates into a state of 

 solubility and available for assimilation. 

 . We see, therefore, the value of decaying vege- 

 table matter in the soil ; for the products 

 of its decomposition, being principally carbonic 

 acid, are eagerly absorbed by the moisture 

 present in the soil. Should this source of carbonic 

 acid be not available to the soil, the necessary 

 quantity is supplied by every rainfall, which 

 dissolves it to a perceptible extent while descending 

 through the atmospheric air, and brings it down to 

 the soil to suit the requirements of vegetable life, 

 As carbon forms the basis of all organic com- 

 pounds, it is necessarily of great importance ; and 

 carbonic acid being the only source from which 

 plants derive it, special attention to the subject is 

 particularly requisite when discussing the natural 

 laws of husbandry. 



Baussingault, a very eminent agricultural che- 

 mist, proved the absorption of carbonic acid by 

 the leaves of plants in the following ingenious 

 manner. Through one of the apertures of a 

 large three -necked receiver he introduced a vine 

 branch bearing about twenty leaves, and then 



