VOL. XI.] PHILOSOPHICAL TRANSACTIONS, 313 



middle or the pith, going horizontally' to the circumference: so that the whole 

 body of wood consists of nothing but small hollow pipes.** 



These pipes, out of which the firm wood is made up, are in many places as 

 clear as crystal,^ and in other places they seem to consist in part, of small 

 globules. ** The great vessels observed and expressed by Dr. Grew, I saw very 

 manifestly to consist of small globules. These great vessels are generally 

 furnished with small membranes, which being cut through, may be seen to lie 

 obliquely in the vessels; and these I conceive to be valves.® 



'° These three sorts of vessels then I have observed not only in ash wood, 

 but also in elm, oak, willow, shumach, lime tree, apple, pear, plum, walnut, 

 hasel tree, &c. And all the vessels which Dr. Grew has represented in ash and 

 other wood, though they differ from each other in size, yet under favour, I 

 ta*e them to be of one sort." I have also made it out, as well as I could, how 



— * These parts, which Mr. Leewenhoeck calls a third sort of vessels. Dr. Grew calls the insertions, 

 and has largely described tliem in all his three books, particularly in his Anatomy of Trunks, p. 20, 

 21, 22; and has clearly expressed them in almost every figure of that book, sc. by white diametrical 

 lines, more agreeable, as he conceives, to nature, which Mr. Leewenhoeck (fig. 10, GH) has ex- 

 pressed by black. These parts he demonstrates, especially from herby plants, to be of the very same 

 substance with the pith. Wherein Signer Malpighi also most clearly agrees with him j see his Idea 

 Anat. Plant, p. 3, 1. 3. Of tliese insertions it is by Dr. Grew further remarked, that they consist of 

 a number of most exquisitely small fibres; which in all less woody, softer, and younger plants, are 

 woven up together into extreme small bladders, which bladders Signor Malpighi has likewise ob- 

 served, caUing them utriculous ; see the forecited place; but not their being composed of such fibres. 

 These bladders being in cleaving a branch many of them cut open. Dr. Grew tells me, he conceives 

 may be taken by Mr. Leewenhoeck for the mouths of vessels. But in most hard woods the bladders, 

 he says, are scarcely to be seen, the said fibres being so closely couched and drawn up together, as to 

 lie rather after the manner of the vessels in the liver, testicles, glands, and other viscera in animals. 

 — ^ Dr, Grew has formerly gathered on probable grounds, that not only the wood, but the whole of a 

 plant consists of pipes; see his Anatomy of Roots, part 2, ch. ult, and Anatomy of trunks, p. 18, and 

 p. 34, 35; see also the latter paragraph of note 5. — ' The same Dr. Grew has said in his Anatomy of 

 Roots, p. — 114. — '^ Dr. Grew has given a further and more particular description of the structure of 

 these vessels; Anatomy of Roots, p. 89, and Anatomy of Trunks, p. 30, and fig. 24. Which, if 

 well minded, will give the reason why they seem, especially in vines, oak, and some other plants, 

 to consist of globules, — ^ Of the same appearance of pithy valves. Dr. Grew makes mention in his 

 first book of the Anatomy of Plants, p. 71, at the beguining. But that in the sap- vessels there are 

 no valves, he proves by divers arguments; see his Anatomy of Trunks, p. 45, 46. He also says, 

 that he has made some experiments, proving that there are no valves neither in the air-vessels. — 

 '"These three general parts Dr. Grew has described, and represented in several figures, showing the 

 different texture of so many several sorts of wood; see Anatomy of Trunks, p. 20 to 30, compared 

 widi the figures and tlie explication of the same. But for what he says of one of the said three parts, 

 which Mr. Leewenhoeck calls a third sort of vessels; see the note 5. — " Dr. Grew has botli de- 

 scribed, and by his figures (Anatomy of Trunks) represented, two sorts of vessels in the wood of ash, 

 and divers other trees. But all these vessels, whose pores or mouths are represented, are indeed of 

 ©ne sort only, excepting in tlie ISth figvire; which made Mr. Leewenhoeck (for want of skill inthe 

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