VOL. XI.] PHILOSOPHICAL TRANSACTIONS. 315 



pith in some places irregular by each other; and the rest of the wood being an 

 infinite number of little vessels"^' or pores. GH are vessels ^^ having their ori- 

 gin from the pith, and terminating in the circumference of the *woody part, 

 viz. when the tree is not growing. These vessels may not always be seen, in a 

 transverse cut, to have *their rise out of G and to end in the circumference H,^ 

 because that in the dissection the knife does not throughout keep just the mid- 

 dle of the body that takes hold of these vessels, from the place of the very be- 

 ginning of them, but in one place, as about C in fig. 9, it will cut through 

 with its sharp point, and in another place the same will pass with its middle, as 

 atD, where it is thickest; and thus the eye sees these vessels to have their be- 

 ginning out of G, and run between G and H into nothing, and again, that the 

 same seem to have their beginning in the middle, and become still broader and 

 broader till they end in H. 



II are the very small vessels,^^ that are accounted to be the firm wood. EK 

 F is the pith of the twig, which likewise cannot be imitated by art, as it con- 

 sists of vesicles or bladders^^ that have six, seven, or eight sides, and lie most 

 curiously with their sides to each other. In some of which bladders I have 

 seen small darkish globules ;^^ and if I had not in some other wood more plainly 

 discovered these globules, it would have been impossible to have observed them 

 in this pith by reason of their extraordinary smallness.^^ 



I beg you, sir, to communicate this to Dr. Grew, with my service to him, 

 and to inquire of him, whether he has seen, as well as I, that the great vessels 

 or pores, which are expressed in his figures, do not consist of globules, as in 

 fig. 8, AB ; as also that in the same do lie oblique membranes or films, which 

 I call valves, as CC, DD; again, whether the particles of the wood, which en- 

 compass the great vessels, be not all of them very small vessels or pores; lastly, 

 whether the strokes which in fig. 10 are denoted by GH coming out of the 

 pith, and running horizontally to the circumference, do not also all of them 



to 30. — ^^ Which Dr. Grew calls tlie true wood, or old sap-vessels, described in his Anatomy of 

 Trunks, p. 22 to 26. — ^* See the note 5. — ^^ See the same thing observed in Dr. Grew's general Ana- 

 tomy of Plants. And an example of the same in the wood of Sumach, Anatomy of Trunks, fig. 

 20} that being of a branch of the first year's growth, as is Mr, Leewenhoeck's, wherein it is much 

 more observable than in older branches, I'he cause of which is that which Dr. Grew calls the braces, 

 and Signor Malpighi, the superequitations of the vessels. — ^4 -jj^g same with those mentioned note 21. 

 — "^^ See Dr. Grew's description of the pith, and therein of these bladders. Anatomy of Roots, part 

 2, and Anatomy of Trunks, part 2, ch. 4. — '® See the same ch. p. 34. — " See the same ch. 32, 

 33. Note, that tliese bladders, whereof the pith consists, Signor Malpighi also observes, but not the 

 fibres, of which fibres (most admirably woven up together) Dr. Grew has discovered the said bladders 

 to be composed) see the same ch. p. 35. — Orig, 



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