071 Vegetable Physiology. 

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167 



merits still better adapted for the purposes of future inves- 

 tigation. 



In watching the flow of the sap, in this case, strange to say, 

 it made itsjirst appearance about the beginning of March, from 

 above, descending t/irough the pith. Shortly afterwards, it ap- 

 peared, also, from aboutJburtee7i layers of the heart wood, around 

 the pith, the exterior or alburnous layers remaining perfectly 

 dry; thus accountiiig for the tap, if I may so speak, made by the 

 sawinyfo-. 24. Little or no appearance of moisture was observed 

 on any part of the corresponding surface belo'-iSO, with the excep- 

 tion of a slight oozing from the externa] or alburnous layers. This, 

 however, was scarcely perceptible. I at present suspect that 

 the principal flow of the ascending sap must have found its 

 way up through the four pillars of alburnous wood alluded to. 

 But I hope to investigate more closely, by future experiment, 

 some points connected with this result. From these experi- 

 ments, it would appear that the life of the tree does not entirely 

 depend upon the preservation of the bark, liber, and alburnum, 

 as two seasons of growth have elapsed since the operation of 

 ringing was performed ; and the trees, with the exception of the 

 one alluded to, as apparently accidentally dead, continue to 



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