40 THE PLANT. 



be a slight difference in the composition of their ashes, 

 but the organic part derived from the atmosphere is 

 much the same in every case, so much so, that they can 

 often be artificially changed from one to the other. 



As an instance of this, it may be stated that at the 

 Fair of the American Institute, in 1834, Prof. Mapes 

 exhibited samples of excellent sugar made from the 

 juice of the corn-stalk, from starch, from linen, and 

 from woody fibre. 



In the plant, during its growth, they are constantly 

 changing. At one time they assume a form in which 

 they cannot be dissolved by water, and remain fixed 

 in their places. 



At another, the chemical influences on which growth 

 depends, change them to a soluble form, and they are 

 carried, by the circulation of the sap, to other parts 

 of the organism, where they may be again deposited 

 in other insoluble forms. For example, the turnip 

 devotes the first season of its growth to storing up 

 in its root a large amount of starch and pectic acid ; 

 in the second season, these substances become soluble, 

 are taken up by the circulation and again deposited 

 in the form of woody fibre, starch, etc., in the stems, 

 leaves, seed-vessels, etc., above the ground. If a 

 turnip root be planted in the spring, in moist cotton, 

 from which it can get no food, it will simply, by the 

 transformation of its own substance, form stems, 

 leaves, flowers and seed. 



Those products of vegetation which contain nitro- 

 gen, are of the greatest importance to the farmer, 

 being the ones from which animal muscle is made. 



