The comparative anatomy of trunks together with an account of their vegetation grounded thereupon; in two parts: the former read before the Royal Society, Feb. 25. 1674/5; the latter, June 17. 1675. The whole explicated by several figures in nineteen copper-plates; presented to the Royal Society in the years 1673. and 1674. By Nehemiah Grew, M.D. and fellow of the Royal Society.

An Account of the VEGETATION OF TRUNKS Grounded upon the foregoing ANATOMY.

HAVING already given the Ana∣tomy of Trunks, I shall next pro∣ceed to see, what use may be made thereof; and principally, to explicate the manner of their Vegeta∣tion. In doing which, that former Method, which I used in shewing the manner of the growth of Roots, I shall not exactly follow. For so, the general parts of the Root and Trunk being the same, and consequently the Nutrition and Confirmation of the Or∣ganical

parts of both, being effected in the same way; I should hereby be obliged to the repetition of many things already said: which would be nauseous and unprofita∣ble unto those, who have been pleased to peruse them. The explication therefore of all those things that more especially be∣long to the Trunk, or are more apparent therein, and not spoken of, or not so fully in my former Books, will be my present task. The chief Heads whereof, shall be these se∣ven following. viz.

• FIRST, the Motion and course of the Sap.
• SECONDLY, The Motion and course of the Air.
• THIRDLY, The Structure of the parts.
• FOURTHLY, The Generation of Li∣quours.
• FIFTHLY, The Figuration of Trunks.
• SIXTHLY, The Motion of Trunks.
• SEVENTHLY, And lastly the Na••••re of Trunks as variously fitted for Mechani∣cal use.

CHAP. I.

FIRST, as to the course of the Sap, there are three parts by which it moveth; sc. the Pith, the Wood, and the Bark. First the Pith; by which the Sap moveth the first year, and only the first year. Or, it is Proprium quarto modo, to the Pith of e∣very Annual growth, and to the Pith of such a growth only, to be succulent. That is, whether of a sprout from a seed, or of a sucker from a Root, or of a Cyon from a Branch; The Pith is always found the first year full of Sap. But the second year, the same individual Pith, always becomes dry, and so it continues ever after.

One cause whereof is, that the Sap-ves∣sels in the Bark, being the first year adja∣cent to the Pith, they do all that time trans∣fuse part of their Sap into it, and so keep it always succulent. But the same Sap ves∣sels the year following, are turned into Wood; and the Vessels which now carry the Sap stand beyond them, in the Bark. So that the Sap being now more remote from the Pith, and intercepted by the new wood, it cannot be transfused with that sufficient force and plenty as before into the Pith; which therefore from the first year always continues dry.

THE SECOND part by which the Sap moves sub forma liquoris, is the Wood. Which yet is not in all Plants, but only in some, and visibly in few; as in the Vine: in which, I say, the Sap doth visibly ascend by the Wood. And this it doth not only the first year, but every year, so long as the Vine continues to grow. But although this ascent by the Wood be every year, yet is it only in the spring, for about the space of a month; sc. in March, and April.

There are many other Trees, besides the Vine, wherein at the same time of the year, (and perhaps in all the other Trees a little before or after) wherein, I say, the Sap ascendeth, though not so copiously, yet chiefly, by the Wood. For taking a Branch of two or three years old, suppose of Sallow, and having first cut it trans∣versly, if the Bark be then in the same man∣ner crushed somewhat hard with the back of the knife, near the newly cut end; the Sap will very plainly rise up out of the ut∣most Ring of Wood. And if it be crushed in the same manner, about an inch lower it will ascend out of every Ring of Wood to the center. Yet at the same time, which is to be noted, there ariseth no Sap at all out of the Bark. Which sheweth the error of that so common opinion, that the Sap

always riseth betwixt the Wood and the Bark. For in the beginning of spring, it riseth, neither betwixt the Wood and Bark, nor in the Bark; but only in the Wood.

THE THIRD part by which the Sap ascends is the Bark, as may be observed in almost any Branch, cut cross in the late Spring and Summer; either as the Sap is∣sueth spontaneously, or upon crushing as a∣foresaid. So that when the Sap ceaseth to ascend, sub forma liquoris, by the Wood, then it begins to ascend by the Bark.

Besides the difference of time, the Organi∣cal parts likewise, by which these two Saps ascend, are divers. For in the Bark, it ascend∣eth visibly only by the Sap-vessels. Whereas in the Wood, it ascendeth only by the Air-vessels. That is to say those Vessels in the Wood, which in the beginning of Spring do often times carry Liquor: when the Tree begins to thrive, and many new parts to be formed and fed, are filled only with Air; sc. a Vegetable Air. The said Vessels in the Wood have likewise a quite different Structure; being composed of spiral, but those in the Bark of rectile∣near Fibers; as we have lately shewed. In which Vessels of the Bark all the specifical liquors of every Tree are chiefly contained.

FROM what hath been said, we may understand, what is meant by Bleeding of

Plants. If we take it generally, it properly enough expresses the eruption of the Sap out of any Vessels; and so, almost all Plants in Summer time, do Bleed: that is, from Ves∣sels either in the Bark or verge of the Pith: the Saps they Bleed, having either a sower, sweet, hot, bitter, or other tast. At which time, the Vessels also, in the Bark of a Vine Branch, do bleed a sower sap.

But that which is vulgarly called bleeding, as in a Vine, is quite another thing; both as to the liquor which issueth, and the place where it issues: that is to say, it is neither a sweet nor sower, but tastless Sap; issuing not from the Air-vessels in the Bark. So that there is as much difference betwixt Bleeding in a Vine, or the Rising of the Sap in any other Tree, in March, and in July; as there is betwixt salivation and an Hae∣morrhage; or betwixt the course of the Chyle in the Lactiferous Vessels, and the Circula∣tion of the Blood in the Arteries and Veins.

NOW the cause whence it comes to pass, that the early spring Sap of a Vine, and other Trees, ascendeth by the Wood, is in that the young Sap-vessels of the Bark, by which the Sap ascendeth all the Summer, are as yet but begun to be formed. So that the Sap having not yet these Vessels to re∣ceive

it, it therefore runs up the Air-vessels in the Wood. But so soon as the said Vessels in the Bark begin considerably to encrease, the Sap quitting the Air-vessels, betakes it self to these, as its most proper Recepta∣cles.

The cause else, why the Vessels of almost all Plants, upon cutting, do yield Sap, or Bleed; is the pression which the Parenchy∣ma makes upon them. For the Pith and other Parenchymous parts of a Plant, have upon the reception of liquor, a Conatus to dilate themselves: as is manifest from spon∣ges, which are a substance of the same na∣ture, and have a somewhat like structure: as also from Cork, which is but the paren∣chyma of a Plant. I say therefore, that the parenchyma being fill'd and swell'd with Sap hath thereby a continual Conatus to dilate it self; and in the same degree, to crush together or contract the Vessels which it surroundeth. And the said Vessels being cut, their actual contraction, and the erup∣tion of the Sap, do both immediately fol∣low.

It may also be noted, that the Trunk or Branch of any Plant being cut, it always bleeds at both ends, upward and down∣wards, alike freely. Which, as well as divers other experiments, plainly shews,

that in the Sap-vessels of a Plant there are no Valves.

FROM what we have now above, and elsewhere formerly said, we may also understand the manner of the ascent of the Sap. As to which I say first, that consider∣ing to what height and plenty, the Sap sometimes ascends; it is not intelligible, how it should thus ascend, by virtue of any one part of a Plant alone; that is nei∣ther by virtue of the parenchyma, nor by virtue of the Vessels alone. Nor by the pa∣renchyma alone. For this, as it hath the nature of a Sponge or Filtre, to suck up the Sap; so likewise, to suck it up but to such an height, as perhaps about an inch, or two and no more.

Nor by the Vessels, alone for the same reason. For although we see, that small glass pipes immersed in water, will give it an ascent for some inches; yet there is a certain period, according to the bore of the Pipe, beyond which it will not rise. We must therefore join both the Vessels and the parenchyma together in the service; which we may conceive performed by them in this manner following.

Let AB be the Vessel of a Plant. Let GH be the Fibers whereof it is composed. Let CEDF be a number of Vesiculae of

the parenchyma, wherewith it is surround∣ed. I say then, that the Sap, in the pipe BA would of it self rise but a few inches, as suppose from D to L. But being sur∣rounded by the Vesiculae DP the said Vesi∣culae being swelled with Sap, press upon the said pipe BA. Which being pervious by its Fibers GH the Vesiculae at the same time filtre or transfuse part of their Sap thereinto; which will therefore be forced to rise higher therein. And the said pipe or Vessel being all along surrounded by the like Vesiculae, the Sap therein is still forced higher and higher. Wherefore the Vesiculae of the parenchyma, are as so many Cisterns of liquor, which being, throughout the length of the pipe, contiguous to it, afford it every where a continual supply of Sap. So that by the supply and pressure of the Cisterns or Vesiculae FD the Sap riseth to L; by those at QL it rises to M; by those at NM, it rises to I; by those at OI, it rises to K; by those at PK, it rises to E; and so to the top of the Tree. And thus far of the motion of the Sap.

CHAP. II.

THE NEXT enquiry to be made, is into the motion and course of the Air. Where this question will first of all be asked; sc. which way the Air first en∣ters the Plant; whether at the Trunk, Leaves, and other parts above ground; or at the Root? I answer, that it enters in part at them all. For the inception, as well as extramission whereof, the pores are so very large, in the Trunks of some Plants, as in the better sort of thick walking Canes, that they are visible, to a good eye, with∣out a glass, but with a glass the Cane seems, as if it were stuck top full of holes with great pins: being so large, as very well to resemble these pores of the skin in the ends of the fingers and ball of the hand.

In the leaves of Pine, they are likewise, through a glass, a very elegant show; standing all, most exactly, in rank and file, throughout the length of the leaves. The figure whereof shall be given hereafter, when I come to the Anatomy of the Leaf.

But although the Air enters, in part, at the Trunk and other parts, especially in some Plants; yet its chief entrance, is at the Root. Even as some parts of Air, may

continually pass into the Body and Blood, by the habit, or pores of the skin; but chiefly, at the mouth. And what the mouth is, to an Animal; that the Root is to a Plant.

Again, if the chief entrance of the Air, was at the Trunk; then, before it could be mixed with the Sap in the Root, it must de∣scend; and so move in a contrary course to the Sap throughout the Plant. As by its reception at the Root, and so its ascent from thence, it hath a more natural and easy motion of ascent: for that the Sap of the same Plant should continually ascend, and the Air descend, would be somewhat strange.

The same is further argued from the few∣ness and smallness of diametral Portions in the Trunk, in comparison with those in the Root: which nature hath plainly there designed, for the separation of the Air from the Sap, as they are both together re∣ceived into the Root. So that the reception and course of the Air, is made on this man∣ner following.

The Air being a springy body, it insinu∣ates into all the Pores and cranies of the earth; and so is perfectly mixed with the soyl. Whereupon, as the Sap enters the Root, more or less Air still intrudes it self

together with it. The liquid portion of the Sap swells and fills up the succulent parts of the Bark. The Airy part is, as was said, separated from the liquid into the Diame∣tral portions. By which it is conveyed from the Bark, and so into the Air-vessels; be∣twixt which Vessels, the said Diametral portions run from the Bark towards the center of the Root. The Air thus received into the Air-vessels, and the reception thereof, by the same means, continued; it is by them advanced into the Trunk. In which advance, it is again, more or less, disbursed into all the parts of the Trunk, as it goes. Partly inwards to the Pith. From whence the Pith is always at length filled with Air. Partly into the Insertions; by which it is conveyed outward into the Bark. Wherein, it is in part transfused through the Sap; and so the rest, with part of the Sap, remitted in perspirations back again into the Air. So that, whereas the Diame∣tral portions in the Root, do serve to con∣vey the Air from the Sap into the Air-vessels: on the contrary the Insertions here in the Trunk serve to convey the Air from the Air-vessels into the Sap. Wherefore, as the Air-vessels advance the Air; or the Airy part of the Sap, and so convey it by the length of the Trunk; so the Insertions filter

it, and convey it by the bredth.

AND that the Insertions have this office of subservience to both kinds of Vessels; doth yet further appear, if we consider, that the Air-vessels are always so postured, as to touch upon the said Insertions, or at least to stand very near them. For either they are large, and so do frequently touch upon them on both sides; as in Elm, Ash, Wallnut &c. Or if they are small; then they either run along in even lines colla∣teral with the said Insertions, as in Holly: or at least, are reciprocally, some on one side, and some on another, inclined to them; as in Apple. By all which means, the Air is more readily conveyed from the Vessels into the Insertions.

Again, a further evidence hereof is that generally, the bigger and the more nu∣merous the Air-vessels are; the bigger, or at least, the more numerous also are the Insertions: especially if the comparison be made (as in all other cases it ought to be, as well as here) betwixt the several species of the same kind. So Corin, which hath small Air-vessels, hath also very small In∣sertions. But the Vine hath both very large: and so for others.

Wherefore, the Insertions minister be∣twixt the Air-vessels and the succiferous; in

the same manner, as the Vesiculae of the Lungs, do betwixt the Bronchiae and the Arteries. That is to say, as in an Animal, the Bronchiae deposite the Air into the Ve∣siculae of the lungs; which administer it to the Arteries: so in a Plant, the Air-vessels deposit the Air into the Insertions, that is into the Vesiculae of the Insertions; by which it is gradually filtred off into the Bark and Sap-vessels.

CHAP. III.

A THIRD enquiry, is into the Gene∣ration and Structure of parts. The man∣ner whereof I have already endeavoured to explicate from the Anatomy of the Root, throughout all particulars. Some whereof I shall yet further clear.

As first the Union of the Bark to the Body of the Tree. Contrary to the common opinion, That they are not continuous; but that the Bark only surrounds the Body, as a scabbard doth the sword, or a glove the hand. As also seemeth to be proved, by the easy sliping of the Bark of Willow, and most other Trees, when full of Sap, from the Wood.

But notwithstanding, this, they are as truly continuous, as the skin of the Body is with the flesh: sc. by means of the Pa∣renchyma, which is one entire Body, run∣ning from the Bark into the Wood, and so uniting both together.

Now the reason why the Bark neverthe∣less slips so easily from the Wood, is plain, viz. Because most of the young Vessels and Parenchymous parts, are there every year successively formed; that is, betwixt the Wood and Bark: where the said parts new∣ly formed, are as tender, as the tenderest Vessels in Animals. And we may imagine, how easy it were at once to tear or break a thousand Vessels or Fibers of an Embrio, of a Womb or Egg.

THE same Vessels of the Bark are al∣ways braced, and gradually fall off toge∣ther with the Parenchyma into the utmost Rind. Hence it is, that the Barks of many Trees are as it were, latticed with several cracks or fissures, of divers sizes, in the fi∣gure of Rhombs: the said fissures repre∣senting the Position and Tract of the Vessels in their Braces. Hence also it is, that the Bark of some Trees, as of Corin, Cherry, &c. falleth off in Rings, sc. because the Sap-vessels are posited in the same manner in the Bark.

The Sap vessels, as they are generated at the inner verge of the Bark: solikewise, in a small quantity, at the utmost verge of the Pith. Hence it is, that is, by the annual accretion of these Vessels, that the Pith is sometimes less in the Trunk, than in the Branches; and less in the elder Branches, than in the younger; and sometimes 'tis al∣most wholly filled up.

SOMETIMES also it breaks and shrinks up, thus making the Trunk a Pipe. The cause whereof, is either the Largness of its Pores, or the Thinness of the sides of the said Pores; upon both which accounts, the Pith doth more easily tear, and upon tearing shrink up, and so become hollow: as in Cichory, Lampsana, Sonchus, Tea∣sel, Brownwort, and others; wherein the Pores of the Pith are large, and the sides of the Pores thin. Whereas, upon contra∣ry accounts the Piths of most Trees, re∣main perpetually entire.

THE Reason why Plants are made thus to become hollow, is partly, for the ripening of the Fruit or Seed; which is the better effected by a more plentiful supply of Air ••••••tinually received into their hol∣low Trunks. By means of which Air, part of the Sap, is dryed up, and the remain∣ing part of it made warmer, and so sooner matured.

Partly, for the better determining the due Age of the Plant. Hence it is, that the greater part of Annual Trunks, are hol∣low: the Air contained in that hollow, drying up the Sap, and shrinking up the Sap-vessels so far, as to hinder the free mo∣tion of the Sap therein; from whence the Plant must needs perish. So that as the Content of the Air-vessels, is a kind of Ve∣getable Air, whose office is to Attenuate, and Ferment rhe Juyces of Plants: so the Con∣tent of these cavities, is a more natural Air, designed chiefly, so soon as it is con∣venient, to dry them up.

Sometimes, though the Pith break, yet not into one pipe, but many cross Mem∣branes, as in Wallnut and Spanish-broom. Because here the dilatation of the Branch, and of the Pith therein, being much less, in proportion, than its growth in length; the Pith therefore, being stretched most by its length, will soonest tear the same way and consequently shrink up into so many Membranes by the bredth of the Trunk.

AGAIN, as to the Air-vessels divers questions may be asked. As how it comes to pass, that they are generally less in the Trunk of the same Plant, than in the Root? The cause whereof is, that here in the

Trunk, they are more under the power of the Air; both that which entereth in at the Trunk, and that which of its own na∣ture ascendeth up into it from the Root. For the Air, as we have elsewhere said, is the mould of the Air-vessels, to the crooked particles whereof the Saline, and other principles concurring to their gene∣ration, do conform. To which they do best, the smaller they are: the Fibers of the larger Air-vessels making greater cir∣cles, and so coming nearer to a right line, answerable to the figure of the Particles; not of the Aerial but of the saline prin∣ciple.

Wherefore as the Air-vessels may be ob∣served still to be dilated or widened to∣wards the lower parts of the Root; the Aerial principle being there less predomi∣nant, and the Saline more: So towards the upper part of the Trunck, to be contracted or grow smaller; the Aerial prniciple be∣ing here more predominant, and the Saline less.

FOR the same cause, it may be obser∣ved, that the Air-vessels of the several years succeeding the second year, are near of one size: but those of the second year, are usually much larger than those of the first, viz. as being under a less power of

the Air. For the first year, the Pith being full of liquor, the Air-vessels themselves, are the only Repositories of the Air. Where∣as after the first year, the Pith becoming dry, or another great Repository for the Air; the Air-vessels, are henceforth filled with a moisture and more vapourous and saline Air, and so made to grow wider.

For the same cause it is, that the dispa∣rity betwixt the Air-vessels of the first and succeeding years, is not, where the Pith is small, so visible. Because being never capable of containing many airy parts of the Sap, the Air-vessels themselves conti∣nue still the chief Receptacles of the Air, and so to be still more equally sized: as in Hazel, Elm, &c. is seen.

Hence the very size of the Pith, hath much influence upon the Air-vessels, and the manner of nutrition, and the Generati∣on of liquors in Plants.

LASTLY, for the above said cause, the time when the Vessels begin every year to be formed or to appear, is always la∣ter; at least, with respect to the season of the Tree. So that whereas the Sap-vessels begin to be formed in spring: these, not till the latter end of Summer, or there a∣bout; at least not till about that time to appear. That is, when the Sap begins to

decrease, and to grow more airy; and so more fit matter for the generation of the said Air-vessels.

CHAP. IV.

UPON the Structure and Formation of the parts, dependeth the genera∣tion of liquors, as was lately intimated. The manner whereof I have formerly shewed, in discoursing of the Root. Yet some things I shall here further explicate. And first, what we have formerly asserted sc. That the concurrence of two specifi∣cally distinct liquors, is as necessary to nu∣trition in Plants, as in Animals. Which appears, as from divers other considerati∣ons, so from the very Structure of a Plant: where in all the organical parts, that is the parenchyma and the Vessels, are every where mixed together per minima, that is, per minimas partes Organicas, or Fiber with Fiber of several kinds. So that every small part of a Tree or of the Bark of a Tree, is as I may say, a sort of Linsy Woolsey. So that there is not the least part of the Sap, which is not impregnate with divers essen∣tial tinctures, as it is continually filtred

from the Fibers of one kind, to those of an∣other; standing every where twisted and stitched up together for the same pur∣pose.

FROM the special nature and structure of the parts, the liquors of Plants are like∣wise specified. The Vessels being the chief Viscera of a Plant. For all liquors in a Plant, are certainly made by that Plant. And since the Plant hath no Viscera (so called) I would then know, what its several liquors are made by? If in the parenchyma, sure∣ly by that parenchyma. If in the Vessels, by the Vessels. And if of divers kinds, by divers kinds of Vessels. So that what the Viscera are in Animals, the Vessels them∣selves are in Plants. That is to say, as the Viscera of an Animal, are but Vessels conglomerated: so the Vessels of a Plant, are Viscera drawn out at length.

AGAIN, as the specifying of the Sap dependeth chiefly on the special nature of the parts: so partly upon the structure of the whole. Whereby every part is still better accommodated with its own Juyce. Thus the Air-vessels are necessary, not only and barely for a supply of Air; but also by their number, size, and position to adjust the quantity of that Air, to the govern∣ment of nutrition, and the generation of

the specificall liquors of every Plant. Which is evident from hence, in that they do not follow the size of the Plant; but are great and many, in some small Plants; and small and few, in some others that are large. So Vines, and Corn, as we have formerly ob∣served, have proportionably a great num∣ber of Air-vessels, and those very large. By which means the Sap is attenuated and less oylie and more copiously impregnated with a subtle, volatile and winy spirit.

For the same reason Canes, which yield that sweet juyce, whereof Sugar is made, and which also aboundeth with a volatile and inflameable spirit: these, I say, ob∣tain the like over proportion of Air-vessels, to what we see in most Plants. Hence also it is, that none of the said Plants have a∣ny considerable Bark; that so the attenu∣ating and subtilizing Air, may have a more easy and plentiful admission at the Trunk also. For which reason likewise the pores of the skin of some Canes are, as hath been observed, remarkably wide.

Hence also it is observable, that of the same species or kindred, those Plants which have the most, and especially the largest Air-vessels; have also the greatest abund∣ance either of a sweet, or of a winy liquor. So in Apple, they are larger than in Crab;

In Warden, larger than in Quince; and in Pear tre, larger than in Warden. So also in Corin, larger then in Goosbery; and in Vine, larger than in Corin: and so in o∣thers.

AND as the Air-vessels, by their Mul∣titude and Largeness, are accommodated to the better making of a winy sap: so by their fewness and smallness, of an oylie. As is remarkably seen in Fir, and other Resi∣niferous Trees: these having, if not the smallest, yet the fewest Air-vessels of all o∣ther Trees.

IF it be asked, how a Plant comes to have any Oyl at all in any part? Since we see, that the Sap by which the Root is fed, seemeth to be nothing else but water: and that many Plants which yield a great deal of stillatitious Oyl, as Mint, Rue, and o∣thers, will yet grow in Water: I say, if it be enquired how this Water, is made Wine, or Oyl? I answer, that there is no such matter. But that the Oyl, and all o∣ther Vegetable principles are actually exi∣stent in, and mixed per minima, though in an extraordinary small proportion with the water. Even as we see the distilled Waters of Anise seeds, Penyroyal, and the like, to be impregnated with their own Oyls, which give the tast and smell to such Waters.

Wherefore as a certain quantity of any salt may be dissolved in Water; beyond which, it will not mix therewith, but re∣mains under its own form: So is there a certain proportion of Oyl, though far less, which may also be perfectly mixed with Water; and is certainly so, more or less, with all the Water in the world. But if that proportion, or degree of impregnati∣on be once exceeded; the particles of Oyl do then, and not till then, gather into a body, and appear under their own form.

I say therefore, that all kinds of vege∣table Principles, are either in or together with the Water, with less difference first re∣ceived into a Plant. But when they are once therein; they are then separated, that is to say, filtred, some from others, in very different proportions and conjunctions by the several parts; the Watery by one part, the Airy by another, the Oily by ano∣ther, and so the rest: and so every Part is the Receptacle of a liquor, become peculiar, not by any Transformation, but only the percolation of parts out of the common Mass or stock of Sap. And so all those parts of the Sap. which are superfluous to any kind of Plant, are at the same time, discharged back by perspirations, into the Air.

And hence, that nature, in the various

percolations and separations of the Sap, may still the better answer her end; hence, I say it is, that she carefully seeth, not only to the special nature of the Organs, by which she doth her work; but likewise to their very position. Thus it is observable, that whereas the Lymphaeducts, which carry a more watery liquor, are still placed on the inner verge of the Bark, next to the Air∣vEssels: the Lactiferous and Resiniferous vessels of Plants, to whose Oylie liquor a mix∣ture of much Air is incongruous; do usu∣ally stand, neither on the inner, nor the outer verge of the Bark; but in the midle. By which means, they are at the greatest distance, and so most secure from the Air; either that which enters the Bark, at the circumference; or from the Wood and Pith.

AND because the Resinous liquors of Plants are more Oylie than their Milky; their security therefore, from the approach of the Air, is yet further contrived. In that in Pine, and other Resinous Trees, the Di∣ametral portions are never found; at least not visible: which yet in other Trees, are conspicuous; being those parts, whose office it is, to introduce the Air from the Wood into the Bark.

AGAIN, the Milky liquors of Plants

being thinner than the Resinous, and having a considerable quantity of water mixed with their oyl; hence it is, that in Milky plants, as in Rhus, there are a greater number of Lymphaeducts; and those stand∣ing nearer to the Milky vessels, than they do in Pine, and the like, to the Resinous. By which means they are better fitted to affuse their aqueous parts more plentifully to the said Milky liquor.

FROM the mixture of watery parts with the Oylie, it comes to pass, that where∣as all Lympha's, Mucilages, and Rosins are transparent; the Aquae-oleous liquors of Plants are milky or white, or otherwise opacous. For the same thing is the cause of the whiteness of Vegetable, as of Animal∣milk: that is to say, a more copious mix∣ture of watery and Oylie parts per minima, or into one body. For even the serous and Oylie parts of Animal milk, when through∣ly separated one from the other, they both become very transparent. So the stillatiti∣ous oyl of anise seeds, is most transparent and limpid, even as water it self: yet there is a known sort of White anise-seed water, as it is commonly called: that is to say, wherein the Oyl, in distillation, ari∣seth and is mixed more plentifully with the water. And the water, wherein the

stillatitious oyl of any Vegetable is dissolved becomes a perfect white Milk; as in this Honourable and Learned Presence, I have formerly had occasion to Demonstrate.

AND that the Milky liquors of all Ve∣tables whatsoever, are likewise more Oylie than their Lympha's, is most certain. For all those Gums, which dissolve in Oyl or water as Galbanum, and the like, are ori∣ginally the Milky Juyces of Plants. And if you take the Milk of any Plant, as for in∣stance, the Milk of common Sumach, or of any tast, bitter, astringent, hot, cold, or a∣ny other whatsoever; and having well dryed it, and then fired it at a candle; it will thereupon burn with a very bright and durable flame, even like that of Tar or Turpentine it self.

FROM what hath been said, we may likewise gather the most genuine import of the word Gum, and the distinction thereof both from a Rosin and a Mucilage. First a Rosin, is originally a Turpentine, or Acido∣oleous liquor, having an exceeding small quantity of watery parts mixed therewith; and which, for that reason, will not be dis∣solved therein, but only in Oyl. Of this kind are Mastick, Benzoine, Taccamahac∣ca, and divers others, commonly, in our Bills to Apothecaries, called Gums. Yet,

in strict speaking they are all so many Ro∣sins.

Secondly a Gum, and every oylie Gum, is originally a milky liquor, having a great∣er quantity of water mixed with its oylie parts; and which, for that reason, will be made to dissolve either in Water or Oyl. Of this kind are Sagapen, Opopanax, Ammo∣niac, and others.

The third sort of Gum, is that which is unoylie, and which therefore dissolveth only in water, as Gum-arabick, the Gum of Cherry∣tree, and others such like. This Gum, though commonly so called, yet is properly but a dryed Mucilage: being originally nothing else but the Mucilaginous Lympha issuing from the Vessels of the Tree. In like man∣ner, as it doth from Cumfry, Mallow, and divers other Plants: and even from the common Cucumer. The Vessels whereof, upon cutting cross, yield a Lympha, which is plainly Mucilaginous, and which being well dryed, at length becomes a kind of Gum, or rather a hardened Mucilage. In like manner, the Gums of Plum-tree, Cher∣ry-tree, and the like, are nothing else but dryed Mucilages. Or, if we will take the word in its widest sense, then all Gums are originally, either a Turpentine, or a Milk, or a Mucilage.

I HAUE made many other Observa∣tions of the tasts, smells, and colours of Plants, and of their contents, since those I last published: and that both for the finding out the true causes of their genera∣tion, and also the applying of them unto Medical use. As also to Mechanical; and particularly the making all sorts of Paints, or Tinctures out of the several parts of Plants, for drawing in Water-colours. In the choice whereof there is much difference to be made. For there are many Plants whose Colours are very clear and radiant, in the Plants themselves; yet when they come to be used, will not hold, but change and and grow foul. But these things, because they belong more properly to the Flower, and other parts of Plants, I therefore o∣mit, till if God give me life and health, I come hereafter to speak of those parts.

And that I might the more fully inform my self and others in these matters; it may be thought requisite, that all kind of exo∣tick parts of Plants, as well as those grow∣ing amongst us, should likewise be exa∣mined. For the procuring whereof, both from the East and West Indies, I have al∣ready bespoke the care of some Persons. To whom I have likewise given direction, how to preserve them in such sort, as that

I may have them fresh, as if they were newly taken from the Plant or Tree. And thus far of the Generation of Liquors.

CHAP. V.

THE Fifth Head, shall be, of the fi∣guration of Trunks. Which also, as well as the making of liquors dependeth upon the Structure of the Parts. As first, al∣most all shrubs (caeteris paribus) have a greater number of Air-vessels; and those of a smaller size; and consequently much spread abroad, as most easily yielding to the magnetick power of the air, accord∣ing as we have more fully demonstrated, in speaking of the Vegetation of Roots: as in Elder, Hazel, Fig, Sumach, and the like. By which spreading, the said Air∣vessels do sooner, and more easily strike into the Bark, and so produce collateral Buds and Branches, and that upon the first rising of the Body from the Root: that is, the Plant becomes a shrub.

BUT if the said Air-vessels are very large, they will not yield so easily to shoot out collaterally; and so the Trunk grows up taller and more entire: as in Oak,

Wallnut, Elm, &c. wherein they are ex∣ceeding large, is seen. Hence also the Vine, if it be but supported, will grow to a prodigious height. And Hops and Bryony, are some of the tallest, amongst all Annu∣al growths: the Air-vessels of all which are very large. Whereas Borage, and other like Plants, although the pores of their pa∣renchyma, are vastly wide, and filled with Sap; yet because their Air-vessels are small, they are therefore but dwarf plants. Wherefore the tallness or advancement of a Plant or Tree, dependeth not upon the plenty of Sap, how great soever, but on the largness of the Air-vessels.

Again, as a Plant or Tree grows either shruby, or Tall, according to the size of the said Vessels: so from their position, doth it grow slender or thick. So where they keep more within the compass of a Ring, as in Elm, and Ash, the Tree in proportion, usu∣ally grows taller and less thick. But where the said Vessels are spread more abroad, and especially are postured in Rays, as they are in Oak the Tree grows very thick. Because the said Vessels thus standing all along nearer to the Insertions, there is a more ready and copious passage of the Air out of the one into the other; and so the Diametral growth of the wood is more pro∣moted.

Lastly, from the same general cause it is, That the Trunks of Vegetables are either Round or Angular. Those of all Trees are round. Because the Bark, being here thick∣er, and the Air-vessels bound up with a greater quantity of Wood; the Air hath not sufficient power to move them, and the Bark with them, into those various positions or figurations, as the Trunks of Plants yield to.

Yet the cause of the various shapes of the Trunks is not the Air alone; but partly the principles of the Plants themselves, in conjunction therewith: according to the predominion whereof, as chiefly of some certain kind of Salt (as I may possibly here∣after more particularly explicate) the Trunk is square, triangular, pentangular, or otherwise figured. And thus much in gene∣rall of the figuration of Trunks.

CHAP. VI.

THE Motions also of Trunks are va∣rious. Principally four; sc. Ascen∣ding, Descending, Horizontal, and Spiral. The cause of the ascent of a Plant, is a cer∣tain Magnetick correspondence betwixt the

air and the Air-vessels of a Plant, the motion and tendency whereof the whole Plant fol∣lows. This I have asserted, and I think, clearly demonstrated in my first and second Books of the Anatomy of Plants. I will here add this plain experiment.

Take a Box of Moulds, with a hole bo∣red in the bottom, wide enough to admit the stalk of a Plant, and set it upon stilts half a yard or more above ground. Then lodge in the mould some Plant, for exam∣ple a Bean, in such sort, that the Root of the Bean standing in the moulds may point upwards, the stalk towards the ground. As the Plant grows, it will follow, that at length the stalk will rise upward, and the Root on the contrary arch it self downward. Which evidently shews, that it is not suf∣ficient that the Root hath Earth to shoot into, or that its motion was only an appe∣tite of being therein lodged, which way soever that be: but that its nature is, though within the Earth already, yet to change its position, and to move down∣wards. And so likewise of the Trunk, though already in the free air above ground, yet now to make a new Motion upwards.

BUT although the natural motion of the Trunk be to ascend; yet is it forced

oftentimes to descend. For the Trunk-Roots growing out of some Plants near the ground, and striking thereinto, do like so many Ropes, pluck the Trunk annually lower and lower into the ground toge∣ther with them; as may be seen in Scro∣phularia, Jacobaea, and many other Plants.

IF these Trunk-roots break out only a∣bout the bottom of the Trunk, as in the a∣foresaid Plants, then the Trunk gradually descends into the earth, and is turned into a Root. But if it be very slender, and the Trunk-roots break forth all along it, then it creeps horizontally; the said Roots tether∣ing it, as it trails along, to the ground; as in Strawberry, Cinquefoyl, Mint, Scor∣dium, &c.

AS to their Spiral motion, it is to be noted; That the Wood of all Convoivula's or Winders, standing more close and round together in or near the center, thereby making a round, and slender Trunk. To the end, it may be more tractable, to the power of the external Motor, what ever that be: and also more secure from break∣ing by its winding motion.

Wherefore, Convovula's do not wind by any peculiar nature or Genius, which o∣ther Trunks have not; but because their parts are disposed so, as to render them

sequaceous to the external Motor. Even as the Claspers of a Vine, having the like Stru∣cture, have also a motion of Convolution: whereas the Branches themselves upon a contrary account, move in a strait line.

The Convolution of Trunks, is made not one, but divers ways; some moving by South from East to West; and others from West to East. Wherefore it seemeth, that as the efficient cause of Convolution, is not within the Plant, but external: so also, that it is not one, but that there are two great efficients of this Motion; s••. the Sun and the Moon. Some winding together with the Sun, in its Diurnal motion, by South from East to West. And others winding with the Moon, in its Monthly motion, from West to East.

This possibly, may also be one sensible way of distinguishing betwixt Solar, and Lunar Plants. Thus far, in general, of the motions of Trunks.

CHAP. VII.

THE last thing I purposed to speak of, is those several Qualities of Trunks, or of Timber, by which they are fitted for

Mechanical use. As hardness, softness, fast∣ness, clevesomeness, toughness, brittleness, durableness; of any of the same qualities compounded. The visible causes whereof are observable partly in the structure of the several parts; sc. the Insertions, Sap∣vessels, and Air-vessels; as to the number, size, or position of any of them. And partly in the nature of the parts; I mean such as is manifest to sense. According to our clear and distinct observing of all which causes, we may understand, wherefore any Wood is made use of for this or that purpose. And also, wherein fitly to apply it to further use. In order to which, a compleat History of the Mechanical uses of Vegetables would very much conduce. I shall for the present give some Instances.

AS first, some Woods are soft, as Deal and Sallow. Yet from different causes. Deal, from the great porosity of the Wood it self, or the large Pores amongst the Sap∣vessels. But Sallow, not from the porosity of the true Wood, but the great number of Air-vessels spread all over it. For the same cause, though they are both soft, yet will not serve for the same purposes; Sal∣low being well wrought upon, which way soever you cut it: but Deal, especially the white Deal, if it be cut cross, it tears, and

will never polish or work smooth.

Again, in Sallow, by the equall spread∣ing of the Air-vessels, the softness is equal or alike in all parts. For which cause it maketh an excellent coal for Painters Scri∣bets. Because it doth not only make a light, but every where a certain stroak, and so doth not disturb the even motion of the hand. For the same cause, Shoo∣makers also make use of it for their Carving-boards. Because being every where equally soft, it turns not the edg of their Knives. Which Deal would presently do; because though very soft in some places, yet in others 'tis hard; that is to say, on the inner verge of every annual Ring of Wood, where the old Sap-vessels grow much more compact and close toge∣ther.

AGAIN, some Woods are soft, but not fast; others are both, as Linn: its softness, depending on the numerousness and equal spreading of the Air-vessels: its fastness, on the closeness of the true Wood, and the shortness, smallness and frequency of the Insertions. For which cause, it is of excellent use for many purposes; and par∣ticularly, for small sculpture: such as may sometimes be seen for the Frames of Look∣ing Glasses, or of smaller Pictures in Water∣colours.

SOME Woods, again, are fast and hard, as Elm. Its hardness depending upon the closeness of the true Wood. Its fastness part∣ly upon the same cause, partly on the small∣ness of the Insertions, partly on the few∣ness of the Air-vessels in proportion with the Wood, and partly the thwart and cross position of many of them. Hence it is, that Elm, of all others, is the most cross-grain'd Timber; that is, cleaveth so unevenly, to and fro, according to the cross position of the said Vessels.

Hence also it cleaveth the most diffi∣cultly. Even then, when it is without a∣ny knots. For which reason it is always used, as best, for the Hub of a great Wheel. As also for Water-pipes, and for Pumps. Not because it is the most durable wood; but because it will not splitt or crack ei∣ther in the working, or afterwards. For the very same reason, it is used for Coffins; that is, because it will not splitt in work∣ing: not because it will endure longest under ground; for Pales are always made of Oak. So also the Ladles and Soles of a Mill∣wheel are made of Elm; as also the Keel of a Boat, sc. least they should splitt: but the other parts are made of Oak.

ON THE contrary as Elm, of all woods, is one of the fastest; So of all hard woods,

Oak is the most Cleavesome, or splitteth the most easily. The cause whereof is, partly the largeness of the Insertions, and partly the diametral or radiated position of most of the Air-vessels: upon both which ac∣counts, whereever a crack is begun 'tis easily continued throughout the Diameter of the Trunk.

AGAIN, some Woods are hard, fast, and tough. So is Ash, and especially Beech-Hard and fast, from some of the same cau∣ses, as Elm. Tough not from the structure, but from the nature of the parts; viz as being a less oylie Wood, and so not Brittle. Wherefore London-Cars have the Rings of their Wheels of Beech; because it tears more difficultly than even Ash it self. Whence also for large screws, there is no Wood like it. But for small screws, of about an Inch diameter, Birch is the best; as being, though not so hard, yet more tough.

THE more Brittle a Wood is, 'tis like∣wise usually the most durable. So Oak, which is not a tough, but very brittle wood, is almost as durable as any. Whereas Beech, Birch, and the like, although very tough; yet for duration, are of no service; for there are no Woods will rot sooner: and therefore, though strong enough, yet unfit to make any standing parts of Building or of Furni∣ture;

especially in wet and moist places. Because, being as is said, unoylie woods, they are apter to imbibe the moisture even of a dank Air; by which moisture, they either rot or breed worms, which destroy them.

HENCE it is, that what we call the Heart of Timber, as it is more brittle, so also more durable; sc. Because more oylie. So that which is called the Sap of Oak, is much more tough than the Heart; although the Heart be more durable. That is to say, the older the Wood is, the watery parts are the more evaporated, the oylie still re∣maining, as a kind of Tincture in the Wood. Even as we see, that the older Seeds of the same kind, are more oylie than those that are green and young. So that the oylie or rosinous parts of the Sap, are a kind of Em∣balming to the Heart, or older part of a Tree, securing it from the destructive im∣pressions of the Air. For the same cause it is, that Oak, Yew, Cocus, Guajacum, &c. Which are oylie woods, have always much Heart: whereas Birch, Alder, Beech, Ma∣ple, which are very unoylie, have never a∣ny Heart.

FROM hence likewise we may under∣stand the cause of the toughness of Flax: what we call Flax, being only the Sap-vessels

of the Bark. And generally, the Bark of any Tree, as of Willow (whereof are usu∣ally made a sort of Ropes) is very tough. The Vessels being here younger, and less oylie than in the Wood. So likewise Hemp, is nothing else but the Sap-vessels of the Bark of the Plant so called. And Scotch∣cloath, is only the Housewifry of the same parts of the Bark of Nettle.

WHENCE it is very probable, that there are many other Plants, as well as the above named, whereof might be made good Toe. And of some, especially in some respects, better than of Flax it self. Be∣cause that even Hemp, although it will not make so fine a Staple, as Flax (for all our fine Hollands are made of Flax) yet Flax, which is but of the same fineness as Hemp, will never, by all the art yet known, be made so white as Hemp is made. The qualities therefore of the best Toe, that can be in na∣ture, are that the Staple be long, small, tough, and white. So that if in the Bark of any Plant, we can find these qualities to excell, we may be sure it will be of bet∣ter use, in some respects, for the making of Cloath than Flax it self.

I WILL conclude with one Instance more, & that is as to Grafting. The good and happy success whereof, doth certainly

depend upon the suitableness or respon∣dence betwixt the several parts of the stock and Cyon; as the Bark, Wood, and Pith: and that both as to the number, size, and position of the said parts, and of their several Pores or Vessels: according to the degrees whereof, the Conjunction (caeteris paribus) will be more or less prosperous. So that of all such Conjunctions as are found to be apt and taking, and which some have learned not without long pra∣ctice and experience; another, only by comparing the Branches of Trees together, may with little trouble, and in much less time, inform himself. By the same means, some Conjunctions which seem to be strange, as Quince and Pear, White-thorn and Med∣lar, &c. do yet, by the respondence of their parts, as well as by experience, ap∣pear to be good. And there is no doubt, but that many Conjunctions not yet tryed, or not known to have been so, may upon the same ground, be tryed with good success.

The chief use of Grafting and Inoculati∣on, is that they accelerate the growth of good fruit. The cause whereof, is the knot, which is always made in the Conjunction. By means whereof all the Sap is strained, and so ascendeth up into the Graff or Bud,

purer and in less quantity; and is therefore better and sooner concocted. Hence, the smaller the Fruit of any Tree, though it be not the best, yet the Sap being there in less quantity, is the sooner ripe. On the contrary, where the Sap ascendeth too freely, it doth not only retard the growth of the Fruit, but produceth Barrenness; as is seen in those luxuriant Branches, where it runs all up to Leaves. Hence also Vines, by Bleeding, become more fruitful: that is, by the effusion of part of the Sap, there is a more easy melioration of that which re∣mains. Even as Phlebotomy doth oftentimes produce a more healthful and better habit of our own Bodies. To conclude, the les∣sening the quantity, and thereby the meli∣oration of the ascending Sap, by knots, is Natures own contrivance; as is seen in Sugar cane, Corn, and other Plants.