132 



Anatomy of the Vine. 



spiral vessels, as they appear within the narrow point of a 

 band, lying next to the medulla. Each of them consists of a 

 single vessel, which is coiled round, so as to form a tube, just 

 as a long piece of very fine wire would be, if twisted upon a 

 round iron rod. The edges of these twists lie on each other, 

 and are united, forming a tube ; otherwise these vessels could 

 not receive and carry forward the secreted juice of the liber, 

 from the horizontal vessels of the alburnum, to the extending 

 shoot in the spring, and afterwards to the leaves. 



The next in the band are the ascending sap-vessels {Jig. 24. 

 b). They are somewhat larger than the spiral, and like them 

 in appearance ; it is only by examining them with a very 

 powerful short-focus glass, that the difference can be dis- 

 tinguished ; for they consist of four vessels coiled round upon 

 each other, forming a tube, instead of one, as was the spiral 

 vessel. By referring to the Jigs. 25. and 26., the difference 



between them will be easily per- 

 ceived. Owing to their trans- 

 parency in their natural state, they 

 are as difficult to be distinguished 

 as the spiral vessels. I should 

 therefore recommend the examiner 

 to place first a lower collet, with a 

 joint and leaf upon it, in the solution 

 of the prussiate of potash, and 

 afterwards in a weak solution of 

 the sulphate of iron, when the 

 spiral and ascending sap vessels of 

 the stalk will be filled with the blue 

 precipitate, which will enable him 

 the more readily to distinguish them. He may find 

 the following hints useful : — Let him procure an 

 ivory tambour needle handle, and place in it a fine 

 common needle, which should be made extremely 

 sharp on an oiled Turkey stone ; let him afterwards 

 press the point against it, to bend it round : with this 

 fine hook he may separate these vessels of the band 

 tolerably well from each other. With needles, first 

 softened in the flame of a candle, I have made for 

 myself, with the assistance of a small anvil, and a 

 light watchmaker's hammer, various small dissecting knives, 

 chisels, &c. The half of these ascending sap-vessels may 

 be seen lying in the alburnum, by their shining, silvery 

 paper-like appearance ; but to detach an entire one, as they 

 are found in the stalk of the leaf, is extremely difficult : in 

 consequence of which, it was a long while before I could 



