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which are capable of maintaining their healthful and growing con- 

 dition. 



Decandolle affirms that plants, like animals, have the power of 

 selecting from their food, as it passes through their vascular sys- 

 tem, such portions as are likely to nourish them, and of rejecting, 

 by their roots when the sap descends, such as are unfit to contri- 

 bute to their support, or would be-hurtful to them if not rejected 

 from the system. He further supposes that after a time the soil, 

 in which a certain kind of plant grows, becomes so loaded with this 

 rejected matter, that the same plant refuses any longer to flourish 

 in it. And thirdly, that though injurious to the plant from which 

 it has been derived, this rejected matter may be wholesome food 

 to plants of a diflerent order, and hence the advantage to be ob- 

 tained from a rotation of crops. For experiment, plant a poppy 

 in a soil that you know to be free from acetic acid, and after it 

 comes to maturity remove it, and you will find a large quantity 

 of the acid where it grew. I have obtained a fine crop of wheat 

 without manure, from a field that had grown clover for three years. 

 I attributed this totheexcrementitious matter rejected by the clo- 

 ver, which, though injurious to it, formed an admirable enricher 

 to the wheat, and came to the conclusion that wheat and clover 

 maybe grown alternately for an indefinite period, the excrement of 

 the one enriching the other. Beets raised on a tobacco field, are 

 unfit for use, being impregnated with the flavor of that detestable 

 destroyer of men's nerves. It is a singular fact that soda and pot- 

 ash diminish in quantity in plants, as they advance towards per- 

 fection. The weight of potash is much greater in unripe, than 

 ripe grapes. 



When seeds germinate they give to the earth acetic acid ; this 

 immediately renders the lime it comes in contact with soluble, 

 and returns to the plant when required to produce a desired 

 eifect ; a wise contrivance of Providence, to store the soil with 

 alkaline matters, which are generally scarce. These enter by the 

 roots, and ascend through the proper vessels until they reach the 

 outer surface of the leaves ; after thus performing their office, 

 they descend by the bark to the extreme ends of the roots, cast 

 off the excrement they may contain, and recommence to circulate 



