The anatomy of plants with an idea of a philosophical history of plants, and several other lectures, read before the royal society / by Nehemjah Grew ...

CHAP. II. Of the ROOT.

HAVING Examin'd and pursu'd the Degrees of Vegetation in the Seed, we find its two Lobes have here their utmost period: and, that having conveyed their Seminalities into the Radicle and Plume; these therefore, as the Root and Trunk of the Plant, still survive. Of these, in their order, we next pro∣ceed to speak; and first, of the Root: whereof, as well as of the Seed, we must by Dissection inform our selves.

2. §. In Dissection of a Root then, we shall find it with the Ra∣dicle, as the Parts of an Old Man with those of a Foetus, substantially, one. The first Part occurring is its Skin, the Original whereof is from the Seed: For that extreme thin Cuticle which is spread over the Lobes of the Seed, and from thence over the Radicle, upon the shooting of the Radicle into a Root, is co-extended, and becomes its Skin.

3. §. The next Part is the Cortical Body. Which, when it is thin, is commonly called the Barque. The Original hereof, likewise is from the Seed; or the Parenchyma, which is there common both to the Lobes and Radicle, being by Vegetation augmented and prolonged into the Root, the same becomes the Parenchyma of the Barque.

4. §. The Contexture of this Parenchyma may be well illustrated by that of a Sponge, being a Body Porous, Dilative and Pliable. Its Pores, as they are innumerable, so, extream small. These Pores are not only susceptive of so much Moisture as to fill, but also to enlarge themselves, and so to dilate the Cortical Body wherein they are: which by the shriv'ling in thereof, upon its being expos'd to the Air, is also seen. In which dilatation, many of its Parts becoming more lax and distant, and none of them suffering a solution of their continuity; 'tis a Body also sufficiently pliable; that is to say, a most exquisitely fine-wrought Sponge.

5. §. The Extention of these Pores is much alike by the length and breadth of the Root; which from the shrinking up of the Cortical Body, in a piece of a cut Root, by the same dimensions, is argu'd.

6. §. The proportions of this Cortical Body are various: If thin, 'tis, as is said, called a Barque; and thought to serve to no other end, than what is vulgarly ascrib'd to a Barque; which is a narrow conceit. If a Bulky Body, in comparison with That within it, as in the young Roots of Cichory, Asparagus, &c. 'tis here, because the fairest, there∣fore taken for the prime Part; which, though, as to Medicinal use, it is; yet, as to the private use of the Plant, not so. The Colour hereof, though it be originally white, yet in the continued growth of the Root, divers Tinctures, as yellow in Dock, red in Bistort, are there∣into introduced.

7. §. Next within this Part stands the Lignous Body: This Lig∣nous Body, lyeth with all its parts, so far as they are visible, in a Cir∣cle or Ring. Yet are there divers extreme small Fibres thereto pa∣rallel, usually mixed with the Cortical Body; and by the somewhat dif∣ferent colour of the said Cortical Body where they stand, may be no∣ted. These Fibres the Cortical Body, and Skin, altogether, properly make the Barque. The Original of this Lignous Body, as of the two former, is from the Seed; or, the Seminal Roots of both the Lobes, be∣ing united in the Radicle, and with its Parenchyma co-extended, is here in the Root of the Plant, the Lignous Body.

8. §. The Contexture hereof, in many of its parts, is much more close than that of the Cortical; and their Pores very different. For whereas those of the Cortical are infinitely numerous, these of the Lig∣nous are in comparison nothing so. But these, although fewer, yet are they, many of them, more open, fair and visible: as in a very thin Slice cut athwart the young Root of a Tree, and held up against the light, is apparent. Yet not in all equally; in Coran-Tree, Goosberry-Tree, &c. less, in Oak, Plums, and especially Damascens, more; in Elder, Vines, &c. most conspicuous. And as they are different in number and size, so also (whereon the numerousness of the Pores of the Cortical Body principally depends) in their shape. For whereas those of the Cortical Body are extended much alike both by the length and breadth of the Root; these of the Lignous, are only by the length; which especially in Vines, and some other Roots is evident. Of these Pores, 'tis also observable, that although in all places of the Root they are visible, yet most fair and open about the filamentous Extremities of some Roots, where about, the Roots have no Pith; as in Fenil. And in many Roots, higher.

9. §. The proportion betwixt this Lignous Body and the Cortical, is various, as was said; yet in this, constant, sc. that in the filamentous and smaller Parts of the Root, the Lignous Body is very much the less; running like a slender Wyer or Nerve through the other surrounding it. Whereas in the upper part, it is often times of far greater quan∣tity than the Cortical, although it be encompass'd by it. They stand both together pyramidally, which is most common to Infant Roots, but also to a great many others.

10. The next Part observable in the Root, is the Insertment. The existence hereof, so far as we can yet observe, is sometimes in the Radi∣cle of the Seed it self; I cannot say always. As to its substantial na∣ture, we are more certain; that it is the same with that of the Paren∣chyma of the Radicle; being always at least augmented, and so, in part, originated from the Cortical Body, and so, at second hand, from the said Parenchyma. For in dissecting a Root, I find, that the Cortical Body doth not only environ the Lignous, but is also wedg'd, and in many Pieces inserted into it; and that the said inserted Pieces make not a meer Indenture, but transmit and shoot themselves quite through as far as the Pith: which in a thin Slice cut athwart the Root, as so many lines drawn from the Circumference towards the Center, shew them∣selves.

11. §. The Pores of the Insertment are sometimes, at least, exten∣ded somewhat more by the breadth of the Root, as about the top of the Root of Borage may be seen; and are thus different from those of

the Cortical Body, which are extended by the length and breadth much alike; and from those of the Lignous, being only by its length.

12. §. The number and size of these Insertions are various. In Hawthorn, and some others, and especially Willows, they are most ex∣tream small; in Cherries and Plums they are Biger; and in the Vine and some other Trees, very fairly apparent. In the Roots of most Herbs they are generally more easily discoverable; which may lead to the observation of them in all.

13. §. These Insertions, although they are continuous through both the length and breadth of the Root; yet not so in all Parts, but by the several shootings of the Lignous Body they are frequently in∣tercepted. For of the Lignous Body it is (here best) observable; That its several Shootings, betwixt which the Cortical is inserted, are not, throughout the Root, wholly distinct, strait and parallel: but that all along being enarch'd, the Lignous Body, both in length and breadth, is thus disposed into Braces or Osculations. Betwixt these several Shootings of the Lignous Body thus osculated, the Cortical shooting, and being also osculated answerably Brace for Brace, that which I call the Insertment is framed thereof.

14. §. These Osculations are so made, that the Pores or Fibres of the Lignous Body, I think, notwithstanding, seldom or never run one into another; being, though contiguous, yet still distinct. In the same manner as some of the Nerves, though they meet, and for some space are associated together, yet 'tis most probable, that none of their Fibres are truly inosculated, saving perhaps, in the Plexures.

15. §. These Osculations of the Lignous Body, and so the intercep∣tion of the Insertions of the Cortical, are not to be observ'd by the traverse cut of the Root, but by taking off the Barque. In the Roots of Trees, they are generally obscure; but in Herbs often more distincty apparent; and especially in a Turnep: the appearance where∣of, the Barque being stripp'd off, is as a piece of close-wrought Net∣work, fill'd up with the Insertions from thence.

16. §. The next and last distinct Part of the Root is the Pith. The substantial nature thereof, is, as was said of the Insertment, the same likewise with that of the Parenchyma of the Seed. And according to the best observation I have yet made, 'tis sometimes existent in its Ra∣dicle; in which, the two main Branches of the Lobes both meeting, and being osculated together, are thus dispos'd into one round and tubular Trunk, and so environing part of the Parenchyma, make there∣of a Pith; as in either the Radicle, or the young Root of the great Bean or Lupine, may, I think, be well seen.

17. §. But many times the Original hereof is immediately from the Barque. For in dissection of divers Roots, both of Trees and Herbs, as of Barberry or Mallows, it is observable, That the Cortical Body and Pith, are both of them participant of the same Colour; in the Barberry, both of them tinged yellow, and in Mallows, green. In cutting the smaller Parts of the Roots of many Plants, as of Borage, Mallows, Par∣sley, Columbine, &c. 'tis also evident, That the Lignous Body is not there, in the least Concave, but standeth Solid, or without any Pith, in the Center; and that the Insertions being gradually multiplied after∣wards, the Pith, at length, towards the thicker parts of the Root, shews and enlarges it self. Whence it appears, that in all such Roots,

the Pith is not only of the same substantial nature, and by the In∣sertions doth communicate with the Barque; and that it is also aug∣mented by it; which is true of the Pith of all Roots; but is moreo∣ver, by mediation of the said Insertions, wholly originated from it; that is to say, from the Parenchymous Part thereof. The various appea∣rances of the Insertions and Pith from the filamentous Parts to the top of the Root, see in Tab. 2. The Pores of the Lignous Body, as it stands entire in the said filamentous Parts, are best seen when they have lain by a night to dry, after cutting.

18. §. A farther evidence hereof are the Proportions betwixt the Cortical Body and Pith. For as about the inferiour Parts of the Root, where the Pith is small, the Cortical Body is proportionably great; so about the top, where the Pith is enlarged, the Cortical Body (now more properly becoming a Barque) groweth proportionably less, sc. because the Insertions do still more and more enlarge the Pith. Likewise the peculiar frame of some Roots, wherein besides the Pith, the Lignous Body being divided into two or more Rings, there are also one or more thick Rings, of a white and soft substance, which stand betwixt them; and are nothing else but the Insertions of the Cortical Body collected into the said Rings; but, towards the top of the Root, being inserted again, thus make a large and ample Pith; as in older Fennel-Roots, those of Beet, Turnep, and some other Herbs, is seen.

19. §. The Pores of the Pith, as those of the Cortical Body, are extended both by the breadth and length of the Root, much alike; yet are they more or less of a greater size than those of the Cortical Body.

20. §. The Proportions of the Pith, are various; in Trees, but small; in Herbs, generally, very fair; in some making by far the great∣est part of the Root; as in a Turnep: By reason of the wide circum∣ference whereof, and so the finer Concoction and Assimilation of its Sap; that Part which in most old Trunks is a dry and harsh Pith, here proves a tender, pleasant meat.

21. §. In the Roots of very many Plants, as Turneps, Carrots, &c. the Lignous Body, besides its main utmost Ring, hath divers of its os∣culated Fibres dispersed throughout the Body of the Pith; sometimes all alike, and sometimes more especially in, or near, its Center; which Fibres, as they run towards the top of the Root, still declining the Center, at last collaterally strike into its Circumference; either all of them, or some few, keeping the Center still. Of these principally, the Succulent part of the Lignous Body of the Trunk is often originated.

22. §. Some of these Pith-Fibres, although they are so exceeding slender, yet in some Roots, as in that of Flower de liz, they are visibly concave, each of them, in their several Cavities also embosoming a ve∣ry small Pith; the sight whereof, the Root being cut traverse, and laid in a Window for a day or two to dry, may without Glasses be obtain'd. And this is the general account of the Root; the declaration of the man∣ner of its growth, with the use and service of its several Parts, we shall next endeavour.

23. §. I SAY THEN, That the Radicle being impregnate, and shot into the Moulds, the contiguous moisture, by the Cortical Body, be∣ing a Body laxe and Spongy, is easily admitted: Yet not all indiscrimi∣nately, but that which is more adapted to pass through the surrounding

Cuticle. Which transient Sap, though it thus becomes fine, yet is not simple; but a mixture of Particles, both in respect of those originally in the Root, and amongst themselves, somewhat heterogeneous. And being lodg'd in the Cortical Body moderately laxe, and of a Cir∣cular form; the effect will be an easie Fermentation. The Sap fermen∣ting, a separation of Parts will follow; some whereof will be impact∣ed to the Circumference of the Cortical Body, whence the Cuticle be∣comes a Skin; as we see in the growing of the Coats of Cheeses, of the Skin over divers Liquors, and the like. Whereupon the Sap passing into the Cortical Body, through this, as through a Manica Hip∣pocratis, is still more finely filtred. With which Sap, the Cortical Body being dilated as far as its Tone, without a solution of Continu∣ity, will bear; and the supply of the Sap still renew'd: the purest part, as most apt and ready, recedes, with its due Tinctures, from the said Cortical Body, to all the parts of the Lignous; both those mixed with the Barque, and those lying within it. Which Lignous Body like∣wise super-inducing its own proper Tinctures into the said Sap; 'tis now to its highest preparaton wrought up, and becomes (as they speak of that of an Animal) the Vegetative Ros or Cambium: the noblest part whereof is at last coagulated in, and assimilated to the like sub∣stance with the said Lignous Body. The remainder, though not united to it, yet tinctur'd therein, thus retreats, that is, by the continual appulse of the Sap, is in part carried off into the Cortical Body back again, the Sap whereof it now tinctures into good Aliment. So that whereas before, the Cortical Body was only relaxed in its Parts, and so dilated; 'tis now increas'd in real quantity or number of parts, and so is truly nourish'd. And the Cortical Body being saturate with so much of this Vital Sap as serves it self; and the second Remainders discharged thence to the Skin; this also is nourish'd and augmented therewith. So that as in an Animal Body there is no instauration or growth of Parts made by the Bloud only, but the Nervous Spirit is al∣so thereunto assistant; so is it here: the Sap prepared in the Cortical Body, is as the Bloud, and that part thereof prepared by the Lignous, is as the Nervous Spirit; which partly becoming Nutriment to it self, and partly being discharged back into the Cortical Body, and diffusing its Tincture through the Sap there, that to the said Cortical Body and Skin, becomes also true Nutriment, and so they all now grow.

24. §. In which growth, a proportion in length and breadth is re∣quisite: which being rated by the benefit of the Plant, both for firm standing and sufficient Sap, must therefore principally be in length. And because it is thus requisite, therefore by the constitution of one of its Parts, sc. the Lignous Body, it is also made necessary. For the Pores hereof, in that they are all extended by its length, the Sap also according to the frame and site of the said Pores will principally move; and that way as its Sap moves, the same way will the generation of its Parts also proceed; sc. by its length. And the Lignous Body first (that is by a priority causal) moving in length it self; the Cortical also moves therewith. For that which is nourish'd, is extended: but whatever is extended, is mov'd: that therefore which is nourish'd, is mov'd: The Lignous Body then being first nourish'd, 'tis likewise first mov'd, and so becomes and carries in it the Principle of all Vegetative motion in the Cortical; and so they both move in length.

25. §. Yet as the Lignous Body is the Principle of Motion in the Cortical; so the Cortical is the Moderator of that in the Lignous: As in Animal Motions, the Principle is from the Nerves; yet being once gi∣ven to the Muscle or Limb, and that moving proportionably to its stru∣cture, the Nerves also are carried in the same motion with it. We sup∣pose therefore, that as the principal motion of the Lignous Body is in length, so is its proper tendency also to Ascend. But being much exceed∣ed both in Compass and Quantity by the Cortical, as in the smaller parts of the Root it is; it must needs therefore be over-born and governed by it; and so, though not lose its motion, yet make it that way where∣in the Cortical Body may be more obedient to it; which will be by de∣scent. Yet both of them being sufficiently pliable, they are thus capa∣ble, where the Soyl may oppose a direct descent, there to divert any way, where it is more penetrable, and so to descend obliquely. For the same reason it may also be, that though you set a Bean with the Radicle upward; yet the Radicle, as it shoots, declining also gradu∣ally, is thus arch'd in form of an Hook, and so at last descends. For every declination from a perpendicular Line, is a mixed motion be∣twixt Ascent and Descent, as that of the Radicle also is, and so seem∣ing to be dependent upon the two Contrary Tendencies of the Lignous and Cortical Bodies. What may be the cause of those Tendencies (be∣ing most probably external, and a kind of Magnetisme) I shall not make my Task here to enquire.

26. §. Now although the Lignous Body, by the position and shape of its Pores, principally groweth in length; yet will it in some degree likewise in breadth: For it cannot be supposed that the purest Sap is all received into the said Pores; but that part thereof likewise, staying about its Superficial Parts, is there tinctur'd and agglutinated to them. And because these Pores are prolonged by its length; therefore it is much more laxe and easily divisible that way; as in slitting a Stick, or cleaving of Timber, and in cutting and hewing them athwart is also seen. Whence it comes to pass, that in shooting from the Center to∣wards the Circumference, and there finding more room, its said origi∣nal Laxity doth easily in divers places now become greater, and at length in open Partments plainly visible. Betwixt which Partments, the Cortical Body, being bound in on the one hand, by the surround∣ing Skin and Moulds, and pressed upon by the Lignous on the other, must needs insert it self, and so move contrary to it, from the Circum∣ference towards the Center. Where the said contrary motions continu∣ed as begun, they at last meet, unite, and either make or augment the Pith. And thus the Root is fram'd, and the Skin, the Cortical and Lignous Bodies, so as is said, thereunto concurrent. We shall next shew the use of the two other Parts, sc. the Insertment and Pith; and first of the Pith.

27. §. ONE true use of the Pith is for the better Advancement of the Sap, whereof I shall speak in the next Chapter. The use I here observe, is for the quicker and higher Fermentation of the Sap: For although the Fermentation made in the Cortical Body was well subser∣vient to the first Vegetations, yet those more perfect ones in the Trunk which after follow, require a Body more adapted to it, and that is the Pith; which is so necessary, as not to be only common to, but con∣siderably large in the Roots of most Plants; if not in their inferiour

parts, yet at their tops. Where though either deriv'd or amplify'd from the Cortical Body, yet being by its Insertions only, we may there∣fore suppose, as those, so this, to be more finely constituted. And being also from its coarctation, while inserted, now free; all its Pores, upon the supply of the Sap, will more or less be amplified: Upon which accounts, the Sap thereinto received, will be more pure, and its fermentation therein more active. And as the Pith is superiour to the Cortical Body by its Constitution, so by its Place. For as it thus stands central, it hath the Lignous Body surrounding it. Now as the Skin is the Fence of the Cortical Body, and that of the Lignous; so is the Lignous again a far more preheminent one unto the Pith; the Sap being here a brisk Liquor, tunn'd up as in a wooden Cask.

28. §. And as the Pith subserves the higher Fermentation of the Sap; so do the Insertions its purer Distribution; that separation which the parts of the Sap, by being fermented in the Pith, were dispos'd for; being, upon its entrance into the Insertions, now made: So that as the Skin is a Filtre to the Cortical Body, so are the Insertions a more pre∣heminent one to the Lignous. And as they subserve the purer, so the freer and sufficient distribution of the Sap: For the Root enlarging, and so the Lignous Body growing thicker, although the Cortical and the Pith might supply Sap sufficient to the nutrition of its Parts next adja∣cent to them; yet those more inward, must needs be scanted of their Aliment; and so, if not quite starv'd, yet be uncapable of equal growth: Whereas the Lignous Body being through its whole breadth frequent∣ly disparted, and the Cortical Body inserted through it; the Sap by those Insertions, as the Bloud by the disseminations of the Arteries, is freely and sufficiently convey'd to its intimate Parts, even those, which from either the Barque or from the Pith, are most remote. Lastly, as the consequent hereof, they are thus assistant to the Latitudinal growth of the Root; as the Lignous Body to its growth in Length; so these Inser∣tions of the Cortical, to its better growth in Breadth.

29. §. Having thus seen the solitary uses of the Several Parts of the Root, I shall lastly propound my Conjectures of that Design where∣to they are altogether concurrent, and that is the Circulation of the Sap.

30. §. That the Sap hath a Double, and so a Circular Motion, in the Root; is probable, from the proper Motion of the Root, and from its Office. From its Motion, which is Descent: for which, the Sap must likewise, some where, have such a Motion proper to it. From its Office, which is, To feed the Trunk: for which, the Sap must also, in some Part or other, have a more especial Motion of Ascent.

31. §. We may therefore suppose, That the Sap moving in the Barque, towards the Pith, through the Insertions, thereinto ob∣tains a pass, Which passage, the upper Insertions will not favour; because the Pith standing in the same heigth with them, is there large, the fermenting and course of the Sap quick, and so its opposition strong. But through the lower it will much more easily enter; be∣cause there, from the smalness of the Pith, the opposition is little, and from the shortness of the Insertions, the way more open. So that the Sap here meeting with the least opposition, here it will bestow it self (feeding the Lignous Body in its passage) into the Pith. Into which, fresh Sap still entring, this being yet but crude, will subside: that

first receiv'd, and so become a Liquor higher wrought, will more ea∣sily mount upwards. And moving in the Pith, especially in the Sap-Fibers there dispers'd, as in the Arterys, in equal altitude with the upper-Inser∣tions; the most volatile parts of all will still continue their direct as∣cent towards the Trunk. But those of a middle nature, and, as not apt to ascend, so being lighter than those beneath them, not to descend neither; they will tend from the Pith towards the Insertions in a Mo∣tion betwixt both. Through which Insertions (feeding the Lignous Body in its passage) it is, by the next subsequent Sap, discharged off into the Cortical Body, and so into the Sap-Fibres themselves, as into the Veins, back again. Wherein, being still pursu'd by fresh Sap from the Center, and more occurring from the Circumference, towards the lower Insertions, it thus descends. Through which, together with part of the Sap afresh imbib'd from the Earth, it re-enters the Pith. From whence, into the Cortical Body, and from thence into the Pith, the cruder part thereof, is reciprocally disburs'd; while the most Volatile, not needing the help of a Circulation, more direct∣ly ascendeth towards the Trunk.

Notes

• Tab. 2. f. 4.
• Tab. 2. f 4. b.
• Tab. 2. f. 5.
• Tab. 2. f. 7 a. b.
• Tab. 2. f. 5.
• Tab. 2. f. 5. & 6.
• Tab. 2. f. 8.
• Tab. 2. f. 9. ••
• Tab. 2. f. 9.
• Tab. 2. f. 8.
• An Account of the Growth of the Root.