ORGANIZED BODIES. 207 



All the nutriment which plants and animals require exists in the rocks, or has existed in 

 them. Of these matters, silex, iron, lime and its various salts, magnesia, phosphates, .etc. are 

 the most common, and these are generally distributed ; while arsenic, mercury or quicksilver, 

 or rather their salts, which are poisons, are only found in very limited quantities, in veins. 

 Now how is it that there is, apparently, a selection of food by plants 1 I may say, in answer to 

 this question, that it arises from the structural differences of species. There are potash plants 

 and lime plants ; that is, some seem to require more potash, or lime, than others. This appa- 

 rent selection of potash, or lime, is due, as already hinted, to the original constitution of the 

 plant; in- other words, it was made of such materials, and its elementary parts were so ar- 

 ranged, that it is adapted to those special nutriments, and hence to take them up. This leads 

 us to adopt the view that there is a speciality in the creation of beings, which extends itself to 

 every species. The tobacco worm thrives upon this nauseous and poisonous weed ; who can 

 doubt its special adaptation to it 1 for it is certain that it can not be ascribed to habit. How 

 is it that marine plants live only where salt abounds 1 It is not because they have become 

 'habituated to it. There are many strong instances of this kind ; but wheat, rye and oats, 

 though allied to each other, are equally special in their structure, by which speciality each one 

 absorbs by its roots (because of their structure) more of the special element they require, than 

 of others which they do not so fully demand.* 



Agriculture has not advanced yet far enough to enable us to adjust the amount of nutriment 

 required by any crop. What agriculturists now aim at, and it is the most they can do, is to put 

 within the reach of each plant all the nutritious elements its nature demands. These elements 

 have been determined by analysis of the different parts of plants; and very many of them may 

 be found and consulted, in the second volume of the Agriculture of New-York. The elements 

 of nutrition are not confined to the soil : the atmosphere is regarded by many as the great 

 store house of carbon, the basis of vegetables. It has not been proved, however, that the car- 

 bon of plants is derived solely from the atmosphere ; and the fact that a great abundance of 

 carbonic acid, and carbonaceous matters, is found in the soil, and enough to satisfy the wants 

 of vegetation, is a fact in itself of sufficient importance to lead us to question the opinion that 

 plants derive their carbon directly from the atmosphere. It is not enough to know that it is 

 stored up in the atmosphere : its solubility in rain water rather indicates the mode by which 

 it may pass into the vegetable tissues. Practically, it would be of little consequence to deter- 

 mine the fact if plants derived their carbon wholly through the leaves ; for, as the amount of 

 carbonic acid in the atmosphere is always the same, and the ability of plants to imbibe it can 

 not be changed, they of course will take in their supply of this material, without cost or labor 

 to the husbandman. In this view carbonaceous manures would lose some of their importance. 



If, on the other hand, plants derive their carbon from the soil, through the medium of the roots, 



♦ 



* All that can be said is, that each species has its own organization, by which it lives its own and peculiar life ; it 

 is merely a statement of an ultimate fact. We may profitably ascertain, by observation, these peculiarities, by aid of 

 the microscope. 



