CH. II. 



COURSE OF THE SAP. 



39 



that the whole of the wood is the conduit for the 



upward course of the sap. 



In April, 1832,1 found a birch-tree in Dyrrham The up- 

 ward sap 



Park, of from 60 to 70 years' growth, which had a f^rough 

 large scar from injuries from cart-wheels. The scar wo^oar"^" 

 might have existed from 15 to 30 years, being perfectly periment.^' 

 indurated, and in parts turned to touchwood. I tapped 

 the scar in the centre with a very large gimlet. I had 

 not pierced an inch before it ran freely wdiile boring. 

 I bored about 3 inches in depth. The tree was 

 about 9 inches through, in the direction of the bore. 

 The dead surface-wood was perhaps a little more than 

 a quarter of an inch in depth. The dropping w^as so 

 frequent as almost to amount to a stream. This could 

 only have flowed from the heart-wood, since no 

 alburnum, or new wood, had been deposited on the 

 scar for about twenty years. 



It is stated that Coulon accidentally observed the 

 sap flowing in ^the heart-wood, in felling some poplar- 

 trees, as I believe, about 1830. His farther proof of 

 boring with an auger, in my opinion, goes for nothing. 

 As the auger must have pierced the sap-wood as well as 

 the heart-wood, who shall say whether the stream which 

 followed came from the sap-wood, or from the heart- 

 wood, or from both, or how much from each? If, 

 according to MM. Coulon, Desfontaines, and Thouin, it 

 came from the heart-wood alone^ the experiment would 

 prove too much. It w^ould prove that the sap-wood is 

 not a conduit for the sap. This is not only nonsense, 

 but undoubted nonsense. 



