A DISCOURSE OF THE COLOURS OF PLANTS Read before the Royal Society, May 3. 1677 - Nehemjah Grew

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 M. D.

Fellow of the Royal Society, and of the College of Physicians.
Printed by W. Rawlins, for the Author, 1682.


(s. 269-278)

A DISCOURSE OF THE COLOURS OF PLANTS
Read before the Royal Society, May 3. 1677.

CHAP. I.

Of the COLOURS of Plants in their Natural Estate.

HAVING formerly made some Observations of the Colours of Plants; I shall now crave leave to add some more to them of the like Nature. None of which, nor any of the Conclusions thence deduced, will, if duly considered, appear contrary to the Hypothesis and Experiments of Mr. Boye, Mr. Des Cartes, Mr. Hook, Mr. Newton or any other, concerning Colours. As not having respect to the Colours of all Bodies in general. Nor to the Body of Colour, which is Light; Nor to the formal notion oí Colours (ad extra) as the Rays of Light are moved or mixed : But to thosè Materials, which are principally necessary to their Production in Plants. Concerning which, the present Discourse shall be reduced to these Three general Heads, scil.

2. §. First, Of those several Colours, which appear in Plants in their Natural Estate.

3. §. Secondly, As they appear upon the Infusion of Plants into several Sorts of Liquors.

4. §. Thirdly, As upon the Mixture of those Infusions, or of any one oí them with some other Liquor, or other Body.

5. §. As they appear in the Plants themselves, it may be observed in the first place, That there is a far less variety in the Colours of Roots, than of the other Parts: the Parenchyma being, within the Skin, usually White, sometimes Yellow, rarely Red. The Cause hereof being, for that they are kept, by the Earth, from a free and open Aer which concurreth with the Juyces of the several Parts, to the Production of their several Colours. And therefore the upper parts of Roots, when they happen to stand naked above the Ground, arc often deyed with scveral Colours : so the tops of Sorrel Roots will turn Red, those of Mullen, Turneps and Radihes, will turn purple, and many others green. Whereas those parts of the same Roots which lie more under Ground, are commonly White.

6. §. As Roots are most commonly White, so the Leaves, Green. Which Colour is so proper to them, that many Leaves, as those of Sage, the young sprouts of St. Johns-wort, and others, which are Redish when in the Bud, upon their full Growth, acquire a perfect Green.

7. §. The Cause of thiss Colour, is the acion of the Aer, both from within, and from without the Plant, upon the Juyces thereof, whereby it strikes them into that Colour.

8. §. By the Aer from without, I mean that which surrounds the Body of the Plant : which is the Cause of its Greeness, not meerly as it is contiguous to it, but as it penetrates through the Pores of the Skin, thereinto; and so mixing with the Juyces thereof, plainly deys or strikes them into a Green.

9. §. By the Aer from within, I mean, that which entring, together with the Aliment, at the Root, thence afcends by the Aer-Vessls, into the trunk, and Leaves, and is there transfused into all the several Juyces, thereby likewise concurring to their Verdure. Whence it is, that the Parts of Plants which lie under Water, are Green, as well as those which stand above it; because, though the ambient Aer, conteined in the Water be but little, yet the want of it is compensated, by that which ascends from the Root.

10. §. And therefore it is observable, that the Stalks of Marsh-Mallow, and some other Plants, being cut transverily, though the Parenchyma in the Barque be white, yet the Sap-Vessels which lie within that Parenchyma, are as Green as the skin it self; feil, because they stand close to the Aer-Vessels. The Parenchyma, I say, which is intercepted from the Aer, without, by the skin; and from the Aer within, by the Sap Vessels, is white ; but the skin, which is exposed to the Aer without, and the Sap-vessels which are next neighbours to that within, are both equally Green. So likewise if a Carrot be plucked up, and suffered to lie sometime in the open Aer; that part which standeth in and near the Centre, amongst the Aer-Vessels, will become Green as well as the skin, all theother Parts continuing of a Reddish Yellow, as before.

The Aer therefore, both from without, and from within the Plant, together with the Juyces of the Plant, are all the concurrent Caufes of its Verdure.

11 §. BUT how doth the Aer concur to the Greenes of Plants? I answe; 5 Not as it is meerly either cold or dry, or moist, nor yet quatenus Aer; but as it is a mixed, and particularly, a Saline Body, that is, as there is a considerable quantity of Saline Parts mixed with those which are properly Aereal. It being plain from manifold Experience; That the several kinds of Salts, are the grand Agents in the Variation of Colours. So that, to speak strictly, although Sulphur be indeed the Female, or Materia fubstrata, of all Colours; yet Salt is the Male or Prime Agent, by which the Sulphur is determined to the Production of one Colour, and not of another.

12. §. If then it be the Aer mixed with the Juyces of a Plant, and the Salt of the Aer, that makes it Green; It may further be asked, what kind of Salt? But this is more hard to judge of. Yet it seemeth, that it is not an Acid, but a Subalkaline Salt; or at least some Salt which is different from a simple Acid, and hath an Affinity with Alkalies.

13. §. One reason why I so judge, is, Because that although all Plants yield an Alkaly, or other Salt different from an Acid, and some in good quantity; yet in most Plants, the Predominant Principle is an Acid. So that the Supply of an Acid Principle from the Aer, for the Production of a Green Colour, as it would be superfluous ; So also ineffectual : a different Principle being requisite to the striking of this, together with the Sulphur, into a Green Colour.

14. §. I suppose therefore, That not only Green, but all the Colours of Plants, are a kind of Precipitate, resulting from the concurrence of the Saline Parts of the Aer, with the Saline and Sulphurious
Parts of the Plants and that the Subalkaline, or other like Saline Part of the Aer, is concurrent with the Acid and Sulphurious Parts of Plants, for the Production of their Verdure; that is, as they strike altogether into a Green Precipitate. Which also seemeth to be confirmed by divers Experiments hereafter mentioned.

15. §. THE Colours of Flowers are various; differing therein not only from the Leaf, but one from another. Yet all seem to depend upon the general Causes aforesaid. And therefore the Colours of Flowers, as well as of Leaves, to result not solely from the Contents of the Plant, but from the concurrence likewise of the ambient Aer. Hence it is, that as they gradually open, and are exposed to the Aer, they still either acquire, or change their Colour: no Flower having its proper Colour in the Bud, (though it be then perfectly formed) but only when it is expanded. So the Purple Flower of Stock-July Flowers, while they are in the Bud, are white, or pale. So Butchelors Buttons, Blew Bottle, Poppy, Red Daisies, and many others, though of divers Colours when blown, yet are all white in the Bud. And many Flowers do
thus change their Colours thrice successively; as the youngest Buds of Ladys-Lookinglass, Bugloss and the like, are all white, the larger Buds are purple or murrey, and the open Flowers, blew: according as they come still neerer, and are longer exposed, to the Aer.

16. §. But if the Colour of the Flower dependeth on the ambient Aer; it may be asked: How it comes to pass then, that this Colour is various, and not one, and that one, a Green? that is to say that all Flowers are not Green, as well as the Leaves? In answer to this Three things are to be premised.

17. §. First, What was said before, is to be remembred, that here the Aer is not a solitary, but concurrent Cause. So that befides the Efficacy of this, we are to consider that of the several parts of the Plant, by which the Contents both Aereal and Liquid are supplied to the Flower.

18. §. Secondly, That in the Lymphaeducts of a Plant, Sulphur is the predominant Principle, and much more abounding than in any other part of a Plant, as also hath been formerly shewed.

19. §. Thirdly, That it appears, according to what we have observed in the Anatomy of the Flower, That the quantity of Lymphaeducts with respect to the Aer-Vessels is greater in the Flower than in the Leaf.

20. §. It semeth therefore, that the Aer-Vessels, and therefore the Aer, being predominant in the Leaf; Green, is therein alfo the predodominant Colour. I say predominant, because there are other Colours lye vailed under the Green, even in the Leafe, as will hereafter appear more manifest.

21. §. On the contrary, the Lymphaeducts, and therefore the sulphur, being more, and the Aer-Vessels and therefore the Aer, less, in the Flower than in the Leaf; the ambient Aer alone is not able to controle the Sulphur so far, but that it generally carrys the greatest port in the Production of the Colour. Yet in different degrees; For if the proportion betwixt the Lymphaeducts and the Aer-Vessels be more equal, the Flower is either White or else Yellow, which latter Colour is the next of kin to a Green. If the Sulphur be somewhat predominant, the Flower will shew it self Red at first; but the ambient Aer hath so much power upon it, as gradually to turn the Red into a Blew. But if the Sulphur be much predominant, then the Acid of the ambient Aer will heighten it to a fixed Red.

22. §. Hence it is, that Yellows and Greens are less alterable, upon the drying of Plants than other Colours; Because the Aer being predominant in their Production, they are the less lyable to suffer from it afterwards. Whereas Reds and Purples, in the Production whereof Sulphur is predominant, are very changeable. So the Red Flowers of Lysimachia, upon drying, turn Purple, and the young purple Flowers of gloss turn Blew. So likewise the Purple of Bilberries, and the Crimson oí baked Damascens, both turn Blew. For being gathered, and so wanting a continued supply of fresh Sulphur, to bear up the Colour against the force of the Aer; it strikes it down at last from Red to purple or Blew. I conclude therefore, that one Principal Cause of the Variety of
Colours in the Flower, is the over proportion of the Lympheducts to the Aer-Vessels, and therefore the dominion of the Sulphur over the Aer, therein.

29. §. If it be objected, that the Aer doth not deepen, but highten the Colour of the Blood: I answer, First, That I am not now speaking of Animal, but of Vegetable Bodies; the same Aer which hightens the Colour of Blood one way, may deepen that of a Flower, another: nay and may highten that of some Flowers too, some other way.

24. §. And therefore, Secondly, it is to be considered, That as there is not one only, but divers Saline Principles in the Aer; so are there also in the several Parts of one Plant; as in the Root, of one fort; in the Leavs, of another; in the Flower, of another; and so in the other Parts. For since the Figuration of the Parts of a Plant dependeth chiefly

[sivu puuttuu; sivulla alkaa luku II]

6. §. I say therefore, that in Blews, Purples and especially Reds, the predominant Principles being Sulphur and Acid, the Oyl either abstracts the Sulphur of itsfelf, or at least, unlocks it from the Acid Parts; whereby both of them are bestowed seperately to their like parts in the Oyl; upon which their disunion the Colour vanishes: that depending, not upon either of them alone, which of themselves are Colourless, but upon both united together.

7. §. On the contrary, a Green Colour not depending on a predominant Acid, but an Alkaly, or some Saline Principle different from an Acid; this will not so easiely be imbibed separately, into the Pores of the Oyl, but only by mediation of their Sulphur. So that being both imbibed without any disunion, they still remein the same green Colour they had before in the Plant.

8. §. Hence also it is, that red Roses being dryed and infused some time in Oyl of Anise Seeds, a more potent Menstruum than Common Oyl; they wholly lose their own Colour, and turn white; the Oyl remaining Limpid, as at the first. That is the Sulphur or that part of it on which cheifly the Red depended, is absorbed separately by the Oyl, and so the Colour vanishes.

9. §. A SECOND Menstruum I made use of, was Water. And First, Alkanet Root, which immediately tinctures Oyl with a deeper Red, will not colour Water in the least.

10. §. Next it is observable, That Water will take all the Colours of Plants in Infusion except a Green. So that as no Plant will by Infusion give a perfect Blew to Oyl ; so their is none, that I know of, which, by Infufton will give a perfect Green to Water.

11. §. But although the Green Leavs will not give their visible Colour, by Infusion in Water; yet they will give most other Colours, as well as the Flowers themselves. So the Green Leavs of Cinquefoyl, give a Tincture no higher than to resemble Rhenish Wine; those of Hyssop, Canary; of Strawberrey, Malaga, of Mint, Muscadine; of Wood-Sorrel, Water and some drops of Claret; of Blood-wort, Water and a dash of Claret; and those of Bawm make a Tincture near as red as ordinary Claret alone. All Aromatick hot Plants, give a yellow-red Tincture, or colorem ex luteo rubrum. All Plants with a Yellow Flower give either a pale citrine or yellowich Tincture; and the like. Yet all give not their Tincture in the same space of time; some requiring a fortnight, others a week, others five, three or two days, and some but one, or half a day. From hence it appears, that the Colours of most Flowers are begun in the Leavs; only Green being therein the predominant Colour, as a veil spred over them, conceils all the rest. But paffing on into the Flower, where the Aer-Vessels, as is aforesaid,
are under the dominion of the Lymphaeductss they shew themselves
distinctly.

12. §. A THIRD and the last Menstruum I made use of, was Spirit of Wine. And here it is to be remarqued; That as Oyl rarely takes a Red, there being but one known Instance of it; nor Water, a Green: So neither Spirit of Wine, a Blew. I have tryed with feveral blew Flowers, as of Lark-heel, Violet, Mallows, Burrage, and others, whereof it will not take the least Tincture.

13. §. Again though no blew Flowers, that I know of, will give a Blew Tinctire to Spirit of Wine : yet having been for some days infused in
in the faid Spirit, and the spirit still remaining in a manner Limpid, and void of the least Ray of Blew; if you drop into it a little Spirit of Sulphur, it is somewhat surprizing to see, that it immediately strikes it into a full Red, as if it had been Blew before: and so, if you drop Spirit of Sal Armoniac or Other Alkaly upon it, it presently strikes it Green. Which further confirms what have been before said of the Caufes of Vegetable Colours.

14. §. It is also observable, That the Green Leaves of Bawm, which give a Muscadine Red, with some Rays of Claret, to Water, gives a pure and perfect Green to Spirit of Wine: and is the only Plant of all that I have yet tryed, which doth the like.

15. §. It is likewise to be noted, That both Yellow and Red Flowers give a stronger and fuller Tincture to Water, than to Spirit of Wine; as in the Tinctures of Cowslip, Poppys, Clove-July-Flowers and Rofes, made both in Water and spirit of Wine, and compared together, is easily seen. So that for Tinctures made with Flowers, whether for Medicines, or other purposes, Water, with respect to the Colour, is the better Menstruum. I say for Tinctures made with Flowers; for there are some other Parts, especially Gumms, as Gamboja, Myrrh and Aloes, which give their Tinctures full and clear, only to Spirit of Wine. Some of which are used by Leather-Gilders, and others, for the washing; over of Silver, so as to give it the Colour of Gold. Thus far of the Colours of Plants as they appear upon Infusion.

CHAP. III.
0f the COLOURS of Plants produced by their Mixture with other Bodies.

THE last general Enquiry proposed to be made, was this, After what manner they would exhibite themselves upon the Mixture of those Infusions, or of any one of them with some other Liquor.

2. §. A strong Infusion, or the Juyce of the Leavs of Rofe-Tree, Raspis, Strawberry, Cynquefoyle, Goosberry, Primrofe, Jerusalem Cowslip, Bearseare, Bearsfoot, Peony, Bistort, Lawrel, Goats-beard, droped upon Steel, make a Purple Tincture. But that of Vine Leaves scarce makcth any Tincture at all. So that there is something else befides Sowerness concurring to the Purple upon Steel.

3. §. Saccharum Satumi droped on a Tincture of Red Rofes, turneth it to a faint pale Green.

4. §. Salt of Tartar droped upon the same Tincture, turneth it to a deeper Green.

5. §. Spirit of Harts Horn droped upon a Tincture of the Flower of Lark-heel and Borage turn them to a verdegreese Green.

6. §. Spirit of Harts Horn droped on most green Leavs doth not change them at all. The like Effects have Aq. Calcis, and Spirit of S. Armoniac.

7. §. These Experiments seem to confirm, That it is fome Alkaline or other like Salt in the Aer, which is predominant in the production of Green in the Leavs of Plants.

8. §. Salt of Tartar droped on the white Flowers of Daisy, changeth them into a light Green. Which as it further confirms the aforesaid Portion; so likewise argues, That Whiteness in Flowers, is not always from the defect of Tincture: but that there may be White, as well as Yellow, Green, Red or Blew Tinctures.

9. §. Spirit of Sulphur droped on the green Leavs of Adonis Flower, Everlasting Pease, and Holy Oak, turns them all Yellow.

10. §. Spirit of Sulphur on a Tincture of Saffron changeth it not.

11. §. Spirit of Sulphur on the Yellow Flower of Crowfoot alters them not. Neither are they changed by the Affusion of Alkalies.

12. §. So that it seemeth, that in all Yeltows, the Sulphureous Acid and Alkaline Parts are all more equal.

13. §. Spirit of Sulphur on a Tincture of Violets turns it from Blew to a true Lacke, or midle Crimson.

14. §. Spirit of Sulphur upon a Tincture of Clove-July-Flowers makes a bright blood Red. Into the like Colour, it hightens a Tincture of Red Roses.

15. §. So that as Alkalys, or other Analogous Salts, are predominant in Greens, so Acids in Reds, especially in the brighter Reds, in the Leavs and Flowers of Plants. Hence it is, that Spirit of Nitre droped upon the Blew Flower of Ladies Looking-Glass, Larkspur, Borage, turns them all Red, sc. into the Red of Common Lychnis. But (which is particularly to be noted) being droped on the faid Red Flowers of Lychnis, alters them little or nothing: because, that very Colour is therein produced by a copious admixture of the like Principle.

16. §. The Summ therefore of what hath now been said, of the Causes of Vegetable Colours, is this: That while their Sulphur and Saline Principles, only swim together, and are not as yet united into one Precipitate, no Colour refults from them, but the Contents are rather Limpid; as usually in the Root, and many other Parenchymous
Parts.

17. §. When they are united, and the Alkaline are predominant, they produce a Green.

18. §. When the Sulphur and the Alkaline are more equal, they produce a Tauny.

19. §. When the Sulphur, Acid and Alkaline, there a Yellow.

20. §. When the Sulphur predominant, and the Acid and Alkaline equal, there a Blew.

21. §. When the Sulphur and Acid are predominant to the Alkaline, then a Purple.

22. §. When the Sulphur predominant to the Alkaline and the Acid to them both, a Scarlet.

23. §. Lastly, When the Acid predominant to the Alkaline, and the Sulphur to them both, a Blood-Red: which is the highest and most Sulphurious Colour in Nature.

24. §. From the Premises, divers Rules do also result for the making of Tintures, either for Medicines, or for any other purposes.

25. §. I shall only add one or two Notes. As first, that of all Colours, Yellows are the most fixed and unfading. As for instance, if you drop cither a Solution of Tartar, or of Spirit of Sulphur upon a Tincture of the Yellow Flowers of Crowfoor, or Adonis, or of Saffron, neither of them will alter their Colour. Which shewes the strength of most Yellows, to resist all manner of impressions from the Aer.

26. §. Again, that the use of Salts, is not only to highten or deepen Colours, but also to fix and make them permanent. As for Instance, The Tincture of Clove-July-Flowers, made either with Water or Spirit of Wine being exposed to the Aer, will often turn into a Blackish Purple. But the addition of a few drops of Spirit of Sulphur, doth not only highten the Colour, but renders it stable and permanent.

27. §. Likewise, of Salts themselves there is choice to be made. For there are some, which although they fix the Colour, yet, will a little give, as we say, and not hold throughly dry; as most Lixivial Salts, and Stillations Acids. But there are some Salts, which will not give in the least, as Alum, that in Lime-Water and some others; which latter, is so far from being moystened, that it is rather petrified
by the Aer. For which reason I take it to be one of the best Liquors for a stable and permanent Green, and some other Colours.

28. §. Amongst all Water-Colours, the rarest, and most difficult to make clear bright and permanent, is a Blew. There are many Flowers of an excellent Blew, as those of Bugloss, Larkheel and others; but they easily fade. And there are very few Flowers that will strike into a Blew by any Liquor; being almost all changeable into Green, Purple or Red. Yet some few there are, in which this Colour maybe produced. As for instance, the Flower of Lathyrus or Parseverlasting; which upon the affusion of Spirit of Harts-Horn is changed from a Peach, to as pure a Blew, as the best Ultramarine: that which hitherto is, I think, wanting in Water Colours. Spirit of Harts Horn was the Liquor I used; but I question not, but that other Alkalies, and particularly Lime-Water, will have the like Effect, and so render it the more stable.

29. §. From what hath been said, we may likewise be confirmed in the use of the already known Rules, and directed unto others yet unknown, in order to the variation of the Colours of Flowers in their Growth. The effecting of this, by putting the Colour desired in the Flower, into the Body or Root of the Plant, is vainly talked of by some: being such a piece of cunning, as for the obtaining a painted face, to cat good store of white and Red Lead.

30. §. The best known Rules are these Two; First, that the Seed be used above any other part, if the variation of the Colour be intended. One reason whereof is, because that part being but very small, the Tinctures of the Soyl will have the greater over proportion to those of the seed. Besides, the tender and Virgin Seed, being committed to the Soyl, will more easily take any peculiar Tincture from it, then an other Part, which is not so susceptive, and hath been tinctured already. All the strange varieties in Carnations, Tulips, and other Flowers are made this way.

31. §. The other Rule is, To change the Soyl, or frequently to transplant from one Bed to another. By which means, the Plant, is as it were; superimpregnated with several Tinctures , which are prolisick of several Colours; which way is taken for Roots and Slips.

32. §. The consideration whereof, and of the foregoing Experiments, may direct us not only in changing the Bed, but also in compounding the Soyl, as by mixing such and such Salts, or Bodies impregnated with such Salts, I say by mixing these Bodies in such a proportion, with the Soyl, as although they have no Colour in themselves, yet may be effectual to produce a great variety of Colours in the Plants they nourish; supplying the Plants with such Tinctures, as shall concur with the Aer, to strike or precipitate their Sulphur into so many several Colours, after the manner above explicated : and so to bring even Natures Art of Painting, in a gerat part, into our own power.