jdiO Pr Davy's Agricultural Discourse. 



supporting themselves, convert organic into inorganic mat- 

 ter, vegetables, in their growth, have the opposite effect ; 

 they create or form organic from inorganic materials, — are, 

 in brief, organizers for the sustentation of animal life. Let 

 lis take an example — A single seed of Quinea corn, weighing 

 about a quarter of a grain, planted in an artificial soil, com- 

 posed of several earths, and containing a little phosphate of 

 lime, and salts of the vegetable and volatile alkali, under fa- 

 vourable circumstances, with sufficiency of moisture from 

 rain, will rapidly vegetate, give rise to a plant many feet in 

 height, and in less than six months yield a ripe head of corn, 

 weighing, in its dry state, 1685 grains, and containing 3537 

 grains of seed ; for such I have found to be the weight of a 

 head of average size, and such the number of the seed it con- 

 tained ; the weight of the seed alone was 1460 grains. What 

 a vast increase is here ! And, if we examine the parts of the 

 plant, its roots, its stem, its leaves, its seed, we shall find 

 them composed of substances differing altogether from the 

 materials which had constituted the food of the plant, a dif- 

 ference depending on a new combination of elements from, 

 in brief, inorganic to organic compounds. 



There is another point of difference, and a very interesting 

 one, between plants and animals, — the effect they have on the 

 atmosphere, comparing the leaves of the one with the lungs 

 of the other. Animals inhale common air, consisting of azote 

 and oxygen ; a portion of the latter disappears, and its place 

 is supplied by carbonic acid, which is a compound of carbon 

 and oxygen, and which is expired ; and consequently, in 

 respiration, animals are consumers of carbon, and its con- 

 sumption is attended with the production of animal heat. 

 Vegetables, on the contrary, absorb or take in carbonic acid, 

 ^nd exhale oxygen by their leaves, and consequently are ac- 

 cumulators of carbon ; and it may be, have the effect in 

 evolving oxygen, of occasioning a reduction of temperature, 

 or of creating a cooling process, the opposite of that of the 

 animal-heating process. Should this be proved to be the 

 case, it will be another example of wise and most happy 

 adaptation. 



I have spoken of vegetables, as organizers, or the pro- 



