124 SCIENTIFIC AGRICULTURE. 



gathered after the stem and foliage are withered in autumn, 

 or before the old root begins to decay in the spring: barks 

 possess more strength if taken after the descent of the sap has 

 ceased, and the cambium has become hardened into wood and 

 bark. 



Some remarks on the collection and preparation of plants 

 for herbariums, and upon botanical analysis, classification and 

 nomenclature, might be made; but they would be of little 

 service, as they would anticipate a step in the science which 

 lies beyond the limits of this treatise. 



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