MOTION OP 1 THE SAP. Q89 



XIII. 



Experiments and Obfervations on the Motion of the Sap in Trees. 

 In a Letter from Thomas Andrew Knight, Efq. to the 

 Right Hon. Sir Joskph Banks, Bart. K.B.P.R.S. 

 From the Philofophical Tranfaclions for 1 801. 



My dear Sir, 



IN the Obfervations on, the Defcent of the Sap in Trees, which Experiments 

 I laft year took the liberty to requeft you to lay before the on the mot j on f 

 Royal Society, I offered a conjecture, that (he veflels of the the % in trees, 

 bark, which pafs from the leaves to the extremities of the roots, 

 were, in their organization, better calculated to carry the fluids 

 they contain towards the roots than in the oppofite direction. 

 I had not, however, at that time, any experiment directly to 

 fupport this fuppofition ; but I thought the forms generally af- 

 fiimed by trees in their growth, evinced the compound and con- 

 tending actions of gravitation, and of an intrinfic power in the 

 veflels of the bark, to give motion to the fluid paffing through 

 them. In the account of the experiments which I have now 

 the honour to addrefs to you, I trufl I fliall be able to adduce 

 fome interefting facts, in fupport of that inference. 



Having lele&ed, in the fpring of 1802, four ftrong (hoots of 

 the vine, growing along the horizontal trellis of my vinery, I 

 deprefled a part of each fhoot, whilft it was foft and fucculenf, 

 about three inches deep, in(o the mould of a pot placed beneath 

 it for that purpnfe ; but without making any wound, or incifiori, 

 in the young (hoots thus employed as layers. 



In this pofition they remained during the fucceeding fummer; 

 and, in the autumn, had nearly filled the pots, which were ten 

 inches in diameter, with their roots. As foon as the leaves had 

 fallen, the layers were difengaged from the parent flocks ; and 

 about five inches of wood, containing one bud, were left, both at 

 the proper and the inverted end of each layer. Every bud was 

 alfo, by previous management, made to (land at an equal diftance 

 from the mould in the pots, and with an equal elevation, of 

 about thirty-fix degrees. About one inch of wood was like- 

 wife left at each end of every layer beyond the buds. 



Vol, X.—Aprsl, 1805. U In 



