206 THE FOOD AND NUTRITION OF PLANTS. 



Hence the perfect adaptation of the two great kingdoms of living 

 beings to each other ; each removing from the atmosphere what 

 would be noxious to the other ; each yielding to the atmosphere 

 what is essential to the continued existence of the other.* 



361. The relations of simple vegetation, under this aspect, to 

 the mineral kingdom on the one hand and the animal kingdom on 

 the other, are simply set forth in the first part of the diagram placed 

 at the close of this chapter. 



362. But, besides this remotely essential office in purifying the 

 air, the vegetable kingdom renders to the animal another service 

 so immediate, that its failure for a single year would nearly depop- 

 ulate the earth ; namely, in providing the necessary food for the 

 whole animal kingdom. It is under this view, that the grand office 

 of vegetation in the general economy of the world is to be contem- 

 plated. Plants are the sole producers of nourishment. They alone 

 transform mineral, chiefly atmospheric materials, they condense air, 

 into organized matter. While they thus produce upon a vast scale, 

 they consume or destroy comparatively little ; and this never in 

 proper vegetation, but in some special processes hereafter to be con- 

 sidered (370). Often when they appear to consume their own prod- 

 ucts, they only transform and transfer them (128, 174), as when 

 the starch of the Potato is converted into new shoots and foliage. 



363. Animals consume what vegetables produce. They them- 

 selves produce nothing directly from the mineral world. The 

 herbivorous animals take from vegetables the organized matter 

 which they have produced ; a part of it they consume, and in 

 respiration restore the materials to the atmosphere from which 

 plants derived them, in the very form in which they were taken, 

 namely, as carbonic acid and water. The portion they accumu- 

 late in their tissues constitutes the food of carnivorous animals ; who 

 consume and return to the air the greater part during life, and the 



'* It is plain, however, that, while the animal kingdom is entirely depend- 

 ent on the vegetable, as no function of animals restores to the atmosphere the 

 oxygen they consume, yet the latter is, in a good degree at least, independent 

 of the former, and might have existed alone. The decaying races of plants, 

 giving hack their carbon to the air and to the soil (333) would furnish food for 

 their successors. And since all the carbonic acid which animals render to the 

 air in respiration they have derived from their vegetable food, it would in 

 time have found its way back to the air, for the use of new generations of 

 plants, without the intervention of animals. At most, they merely expedite 

 its return. 



