370 



RINGING. 



iri 



the physiological nature of the operation so well that I cannot 

 do better than quote his words. 



" The true sap of trees is wholly generated ia their leaves, 

 from which it descends through their bark to the extremities 



of their roots, depositiug in its 

 course the matter which is suc- 

 cessively added to the tree, whilst 

 whatever portion of such sap is 

 not thus expended sinks into the 

 alburnum, and joins the ascend- 

 ing current, to which it commu- 

 nicates powers not possessed by 

 the recently absorbed fluid. When 

 the course of the descending cur- 

 rent is intercepted, that naturally 

 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 consistenily 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, ac- 

 counts, I conceive, satisfactorily 

 Kg. Lxviii. fo^ ^^ increased production of 



blossoms, and more rapid growth 

 of the fruit upon the decorticated branch ; but there are 

 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 

 eonsequence operates less actively in impelUng the ascending 

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

 thi'ough the decorticated space. The parts which are above it 



