CONTENTS. 



xix 



animals : does not obtain in any kind of vegetables. In- 

 ferences. 



Additional considerations regarding the absence of this 

 process of molecular nutrition in plants, intended to shew 

 the identity between the perennial tree and the mere annual 

 in respect of their vitality, and the difference between plants 

 and animals. These considerations drawn from the different 

 objects for which plants and animals respectively have been 

 created. Obj ects of animal existence. Obj ects of vegetable 

 existence — illustrations — corn-producing plants, timber- 

 producing plants — the objects for which each of these exists 

 accomplished year by year. Inferences as to the vitality 

 of the persistent annual stems and roots of trees. More- 

 over, after the year they are formed, these stems and roots 

 undergo no change in the way of growth or extension. 



LETTER X. ...... 92 



The proofs hitherto adduced may be thought incomplete or 

 insufficient. Although the stems and roots undergo no 

 nutritive or other organic change after the year of their 

 formation, the living sap moves or circulates through them. 

 Hence a presumption that the parts in Question still con- 

 tinue to be possessed of vitality. That presumption, 

 however, erroneous. Why : the stems and roots of the 

 previous year no otherwise concerned in the movement of 

 the sap than passively and as mere channels of transmission. 

 The circulation of the sap a vital process, and due to vital 

 agency ; but this agency seated in the living and growing 

 - parts — buds, leaves, ca^mbium, and spongioles of the roots, 

 and the cause both of the ascending and the descending 

 currents. No good grounds exist for ascribing vitality or 

 vital agency to the old stems and roots. Further, in the 

 course of time, these stems and roots undergo decomposition 

 without this affecting the vitality of the growths siibse- 

 quently evolved from the buds. 



LETTER XI 103 



Arguments in support of the Corporation-theory of trees, de- 

 rived from the concurring and independent views of various 



