246 



XLI. PHYSIOLOGICAL OBSERVATIONS UPON THE EFFECTS OF PAR- 

 TIAL DECORTICATION, OR RINGING THE STEMS OR BRANCHES, OF 

 FRUIT-TREES. 



[Read before the HORTICULTURAL SOCIETY, June 6th, 1820.] 



IT has not, I think, been sufficiently explained by what means the 

 obstruction, or prevention, of the passage of the fluids of trees through 

 their bark operates in occasioning an increased production of blossom, 

 and a more rapid growth, and more early maturity, of the fruit : the 

 gardener is in consequence, in many cases, unable to foresee whether he 

 is likely to obtain benefit, or to sustain injury, from the operation ; and 

 he is wholly without the means of knowing how to adopt his mode of 

 operating, with any degree of precision, to the object which he has in 

 view. I therefore address the following observations under the impression 

 that the hypothesis which I have advanced in different papers in the 

 Philosophical Transactions will afford a satisfactory explanation of the 

 cause of all the above-mentioned effects. 



According to that hypothesis, the true sap of trees is wholly generated 

 in their leaves, from which it descends through their bark to the 

 extremities of their roots, depositing in its course the matter which is 

 successively added to the tree ; whilst whatever portion of such sap is not 

 thus expended sinks into the alburnum, and joins the ascending current, 

 to which it communicates powers not possessed by the recently-absorbed 

 fluid. When the course of the descending current is intercepted, that 

 necessarily stagnates, and accumulates above the decorticated space ; 

 whence it is repulsed, and carried upwards, to be expended in an 

 increased production of blossoms and of fruit ; and, consistently with 

 these conclusions, I have found that part of the alburnum which is 

 situated above the decorticated space to exceed in specific gravity, very 

 considerably, that which lies below it. The repulsion of the descending 

 fluid therefore accounts, I conceive^ satisfactorily for the increased 

 produce of blossoms, and more rapid growth of the fruit, upon the 

 decorticated branch ; but there are other causes which operate in 

 promoting its more early maturity. The part of the branch which is 

 below the decorticated space is ill supplied with nutriment, and ceases 

 almost to grow : it in consequence operates less actively in impelling the 

 ascending current of sap, which must also be impeded in its progress 

 through the decorticated space. The parts which are above it must 

 therefore be less abundantly supplied with moisture ; and drought, in 

 such cases, always operates very powerfully in accelerating maturity. 



