The anatomy of plants

HE next general Part of a Branch, is the Wood; which lyeth betwixt the Barque and the Pith. And this likewise evermore consisteth of Two General Parts, sc. of a Parenchymous Part, and that more properly called Lignous. The Parenchymous Part of the Wood, though much diversifyed, yet in the Trunks of all Trees whatsoever, hath this property, To be disposed into many Rays, or Diametral Insertions, running betwixt so many Lignous Portions, from the Barque to the Pith: as in any of the Quarters here before us may appear.

2. §. But these Insertions are much diversifyed, according to the several Sorts of Plants. So in Barberry, Ash, Pine, Worm-wood, they are less numerous. Tab. 22, to 35. In Elm, Wallnut, Fig, Sumach, they are more. And in Holly, Pear, Plum, Apple, Oak, Hazel, are most numerous.

3. §. The same Insertions, in Barberry, Wormwood, and some in Oak, are very Thick. In Pine, Fig, Ash, of a middle Size. In Pear, Holly, and most of them in Oak, are exceeding Small. Ibid. Again, in Barberry, Elm, Ash, Sumach, Fig, they are of an Equal Size. In Holly, Hazel, Pear, Plum, Oak, they are very Unequal: some of those in Holly, being Four or Five times thicker than the rest; in Plum, Six or Seven times; and in Oak, Ten times at least.

4. §. In some Plants, they are Equidistant; in others, not: in some, the Great ones are Equidistant; in others, the Lesser; in others, both; in some, neither. Which Varieties are not accidental; but constant to the Species in which they are severally found.

5. §. They are not always visibly continued from the Circumference to the Centre of the Wood: but in some Branches, as of Sumach; and in most Trunks of many years growth, declining, in some places, Tab. 34. under or over, from a Level, are thereby, upon a Transverse Section, in part cut away.

6. §. They have yet one more Diversity, which is, That in divers of the aforesaid Branches, they run not only through the Wood; but also shoot out beyond it, into some Part of the Barque, as in Elm, Sumach, Wormwood, &c. Tab. 28, 34, 35. Whereas in Pine, and some of the rest they either keep not distinct from the other parts of the Parenchyma of the Barque; Tab. 32. or are so small, as not to be distinguished there from.

7. §. The Texture likewise of these Insertions is somewhat various. Tab. 35. For in Wormwood, and most Herbs, they are manifestly composed of small Bladders: differing in nothing from those of the Barque or Pith, saving, in their being much less. Yet in Herbs, they are much larger than they are in Trees. Tab. 36, 37. And in many Trees, as Apple, Pear, Plum, Pine, &c. they are either quite lost, or so squeezed and pressed together by the hard Wood standing on both sides, as to be almost undiscernable.

8. §. So that although the Parenchyma of the Barque or Pith, and the Insertions in the Wood, are of the same Specifick Nature or Substance: yet there is this difference betwixt them; That the Fibres of the former, are so Netted together, as to leave several round Vacuities; or to make a great many little Bladders, whereas, in the latter, they are usually so far crowded up, as to run (as when a Net is stretched out) like a Skein of Parallel Threds.

9. §. Of these Insertions in the Wood, it is further observable, That they do not only run betwixt the Lignous Portions; but that many of their Fibres are likewise all along distributed to the several Fibres, Tab. 40. of which the Lignous Portions consist, and are interwoven with them; both together thus making a piece of Linsy-Woolsy Work, or like many other Manufactures in which the Warp and the Woof are of different Sorts of Stuff: as in the end of the Fourth Chapter is further explained.

10. §. THE WOOD is likewise compounded of Two Sorts of Bodies; That which is strictly Woody; and the Aer-Vessels mixed herewith. The true Wood is nothing else but a mass of antiquated Lymphæducts, viz. those which were originally placed on the inner Margin of the Barque. For in that place, there grows, every year, a new Ring of Lymphæducts. Which losing its original softness by degrees, at the latter end of the year, is turned into a dry and hard Ring of perfect Wood.

11. §. So that every year, the Barque of a Tree is divided into Two Parts, and distributed two contrary ways. The outer Part falleth off towards the Skin; and at length becomes the Skin it self. In like manner, as hath been observed of the Skin of the Root. Or as the Cuticula in Animals, is but the efflorescence of the Cutis. I say, that the elder Skin of a Tree, is not originally made a Skin; but was once, some of the midle part of the Barque it self, which is annually cast off, and dryed into a Skin: even as the very Skin of an Adder, upon the gradual generation of a new one underneath, in time, becomes a Slough. The inmost portion of the Barque, is annually distributed and added to the Wood: the Parenchymous Part thereof making a new addition to the Insertions within the Wood; and the Lymphæducts a new addition to the Lignous pieces betwixt which the Insertions stand. So that a Ring of Lymphæducts in the Barque this year, will be a Ring of Wood the next; and so another Ring of Lymphæducts, and of Wood, successively, from year to year. So the Table, for an Apple-Branch, Tab. 25, 24, 34, 28. sheweth a quarter of a Slice of a Branch cut transversly, of Three years growth: That of Barbery, of Two; That of Sumach, of One only; That of Elm, of Five.

12. §. Hereby two things maybe the better noted. First, the difference betwixt the degrees of the annual growths of several Trees: three years growth in an Oak, being as thick as five in an Elm. Tab. 33, 28. Secondly, the difference betwixt the Annual growths of the same Tree; being not of a constant proportion, but varying in thickness, as it should seem, according to the season of the year: whereby it may appear, what season, or kind of year, doth most of all favour, the latitudinal growth, or the thickening of any Tree.

13. §. The Lymphæducts thus antiquated or turned into Wood, do rarely, if ever, Bleed: but only transmit a kind of Dewy or Vaporous Sap. And some of them, as in the Heart of some Trees, it is probable, That they transmit not any Sap, either in the form of a Liquor, or a Vapour: and so being gradually deprived of their Watery Parts, become the Heart.

14. §. There is this further variety in the Wood; represented in Walnut, Fig and Oak. That some certain parcels hereof, make either several small and white Rings, as in Oak; or else divers white and crooked Parcels, transverse to the Insertions, as in Wallnut and Fig. Tab. 30, 31, 33. For it seemeth, that, at least,in many Trees, some portion of all the Kinds of Vessels in the Barque, are not only annually distributed to the Wood, but do likewise therein retain the same, or somewhat like Position, which they originally had in the Barque. So that as all those bigger and darker Portions of the Wood, were originally, the Radiated Lymphæducts of the Barque: so the little white Circles, or Parcels of Circles, in the same Wood, were originally another sort of Sap-Vessels in the Barque, sc. those which have a circular Position therein.

15. §. In the Branches of Fir, Pine, and others of the same Kindred, there are some few Turpentine-Vessels scattered up and down the Wood; Tab. 32. and represented by the larger Black Spots. Which Vessels are eadem numero, the self same, which did once appertain to the Barque; and do even here also in the Wood, contain and yield a liquid Turpentine. Only, being pinched up by the Wood, they are become much smaller Pipes.

16. §. THE Aer-Vessels, with the Insertions, and true Wood, altogether make up That, which is commonly called, The Wood of a Tree. The Aer-Vessels I so call, not in that they never contain any Liquor; but, because all the principal time of the growth of a Plant, when the Vessels of the Barque are filled with Liquor, these are filled only with a Vegetable Aer.

18. §. The Varieties hereof are very many; in respect both of their Number, Size, and Position; being, as to these, the same, in no two Sorts of Plants whatsoever. First in respect of their Number. So in Hazel, Apple, Pear, they are very numerous; but in different degrees: and are represented in the Figures already referred to, by all the black spots in the Wood. Tab. 23, 25, 26.
22, 24, 27.
29, 30, 33. 32. In Holly, Plum, Barberry somewhat numerous. In Oak, Ash, Walnut fewer. In Pine, and others of that Kindred, very few; sc. fewer than in any other kind of Plant.

19. §. Secondly, in respect of their Size; which from the first or greatest, to the least, may be computed easily to about Twenty Degrees. Thus, many of those in Elm, Ash, Wallnut, Fig, Oak, are very large. In Barberry, Plum, not so large. In Hazel, Sumach, smaller. In Holly, Pear, of a still smaller Size. Tab. 28, 33.
22, 26. So that many of those in Elm, or Oak, are Twenty times bigger, than those in Holly or Pear.

20. §. In an ordinary joynted Cane, they are so wide, that if you take one a yard, or a yard and ½ long, and putting one end into a Basin of Water, you blow strongly at the other; your Breath will immediately pass, through the Aer-Vessels, the length of the Cane, so as to raise up the Water into a great many Bubbles.

21. §. And as they have a different Size in divers Kinds of Plants; so likewise, according to the place where they stand, in the self same. So in Holly, Hazel, Apple, their Size is more equal throughout the bredth of the Tree. Tab. 22, 23, 25.
24, 28, 29.
33. But in Barberry, Elm, Oak, Ash, very different: Not fortuitously, but always much after the same manner. For in all the last named Branches, the Aer-Vessels stand in the inner margin of each annual Ring, are all vastly bigger, than any of those that stand in the outer part of the Ring.

22. §. Thirdly, these Aer-Vessels are also different in their Situation. So in Apple, Wallnut, Fig, they are spread all abroad in every annual Ring; Tab. 25, 30, 31. not being posited in any one certain Line. In others, they keep more within the compass of some Line or Lines; either Diametral, or Peripheral. Tab. 22. 23, 32. So in Holly they are Radiated, or run in even Diametral Lines betwixt the Pith and the Barque. So also are some of them in Hazel; and some few in Wallnut.

23. §. Whether they stand Irregularly, or are Radiated, it is to be noted, That Nature, for the most part, so disposeth of them, that many of them may still stand very near the Insertions. So in Apple, she will rather decline making an even Line; or in Holly, will rather break that Line into Parcels, than that the Aer-Vessels shall stand remote from the Insertions. To what end this is done, shall be said hereafter.

24. §. Again, in Ash, the Aer-Vessels are none of them Radiated, but most of them stand in Circles on the inner Margin of every annual Ring. Tab. 24. 29. 28. 26, 27. Which Circle is sometimes very thick, as in Ash and Barberry. In others but thin, the Vessels standing, for the most part, single throughout the Circles; as in Elm. Sometimes again, they both make a Circle, and are also spread abroad; as in Pear and Plum.

25. §. Those likewise which are spread abroad, are sometimes Regularly posited. Tab. 24. So in Barberry, besides those larger, that make the Circle, there are other smaller ones, that stand, in oblique Lines, athwart one another; almost like a Bend, or sometimes, an entire or broken Saltyr in an Escutcheon. Tab. 33. 38. In Oak, they make rather certain Columns, in the posture of the Pale. And in Elm, they make, as it were, many cross Parcels, in the posture of the Fess.

26. §. This great difference in the Size and Position of the Aer-Vessels, in the same individual Plant, is one ground, for which, I think it probable, That there are divers Kinds of Aer-Vessels, as well as of Sap-Vessels. Even as in Animals, there are divers Kinds of Organs for Spiration, and the separation of Aer: Fishes having their Branchiæ; Land-Animals their Lungs; and those in Frogs, &c. being of a somewhat peculiar Kind.

27. §. THE Form and Texture of these Vessels, and the various ways whereby they may be best observed, I have already described and shewed in my Anatomy of Roots. P. 1. c. 4. As to their Form, one thing remarqued was this; That they are never Ramified, but distinctly continued from one end of a Plant, small or great, to the other: as the Nerves are in Animals. A further and easie proof whereof, may be made, only by holding up a piece of an ordinary Cane, about ½ a foot long, cut very smooth at both ends, against a full light: whereupon, if you keep it in a straight Line betwixt the Light, and the cast of your Eye, and then look steadily, you may see quite through it, that is, through the Aer-Vessels, which run straight along the Cane from end to end.

28. §. As to their Texture; whereas, oftentimes, the Aer-Vessels appear to be unroaved in the form of a very small Plate, it is to be noted, That it is not only of different bredth, in divers Plants, and usually much broader in the Root, than in the Trunk: but also, that in the Trunk, many times, the said Vessels are unroaved or resolved, not in the form of a Plate, but of a Round-Thred. The Causes of which Diversity, are principally Three; viz. The Weftage of the Fibres of which the Aer-Vessels consist; The deference betwixt the said Fibres, or betwixt the Warp and the Woof; And the different Kinds of Woof.

29. §. By the Weftage of the Fibres, it is, That the Vessels, oftentimes, unroave in the form of a Plate. As if we should imagine a piece of fine narrow Ribband, to be woun’d spirally, and Edg to Edg, round about a Stick; and so, the Stick being drawn out, the Ribband to be left in the Figure of a Tube, answerable to an Aer-Vessel. For that which, upon the unroaving of the Vessel, seems to be a Plate, Tab. 39. or one single Piece, is, as it were, a Natural Ribband, consisting of several Pieces, that is, a certain number of Threds or Round Fibres, standing parallel, as the Threds do in an Artificial Ribband. And as in a Ribband, so here, the Fibres which make the Warp, and which are Spirally continu’d; although they run parallel, yet are not coallescent; but conteined together, by other Transverse Fibres in the place of a Woof.

30. §. And as the said Fibres are transversly continued, thereby making a Warp and Woof: So are they (as in divers woven Manufactures) of very different Bulk; those of the Former, being much bigger, and therefore much stronger, than those of the Latter. By which means, as Cloth or Silk will often Tear one way, and not another; so here, while the Warp or those Fibres which are Spirally continued, are usually unroaved without breaking; those smaller ones, by which they are stitched or woven together, easily tear in sunder all the way.

31. §. And because the Fibres of the Woof, are themselves also of different Bulk; therefore it is, That where they are more sturdy, as usually in the Root, they require a greater quantity of Warp, that is, a broader Plate, to overmatch them. Whereas, where they are more extream small, as in the Trunk and Leaves, one Thred of the Warp, that is, one Spiral Fibre, will be strong enough of it self, and so, sometimes, be singly unroav’d.

32. §. From the extream Tenuity of these Fibres, it is, That they are very rarely discern’d, and not without the greatest difficulty. As also, from their great Tenderness; whereby not enduring to be drawn out, they all break off close to the Sides of the Spiral ones. In the Pith, the like Transverse Fibres are a little more visible: which first conducted Me to the notice of them here also.

33. §. All the Fibres of the Aer-Vessels, both the Warp and the Woof, are of the same Substantial Nature with the Pith and the other Parenchymous Parts of a Plant. From whence it is, That whereas the Towy Parts of a Plant, whereof all Linen Manufactures are made, are very Strong and Tough; these, as is abovesaid, are extream Tender and Brittle, like those of the Pith and all the Pithy Parts. To which therefore, the Aer-Vessels are to be referr’d. And the Content of both, is oftentimes the same.

34. §. From whence, we have a further proof of what I have formerly asserted, which is, That in all Plants, there are Two Substantially different Parts, B. 1. c. 7. §. 13. 14. and no more than Two, viz. the Pithy, and the Towy or Lignous Parts.

35. §. From hence also we have some ground to conjecture, That so many of the Aer-Vessels, at least, which are not formed with the seed, but post-nate, are originated from the Parenchymous Parts; which seem by some alteration in the Quality, Position and Texture of the Fibres, to be Transformed into Aer-Vessels, as Caterpillars are into Flies. And as the Pith it self, by the Rupture and Shrinking up of several Rows of Bladders, doth oftentimes become Tubulary: So is it also probable, that in the other Parenchymous Parts, one single Row or File of Bladders evenly and perpendicularly piled; may sometimes, by the shrinking up of their Horizontal Fibres, all regularly break one into another and so make one continued Cavity; or a Tube, whose Diametre is the same with that of the Bladders, wherof it is composed. All which, will appear more probable, and what hath been said, be yet better understood, when we come, in the next Chapter, to the Description of the Pith.