The anatomy of plants

AVING formerly made some Observations of the Colours of Plants; Idea, §. 27. and Anat. of R. P. 2. §. 65, &c. 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. Boyle, 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 of Colours (ad extra) as the Rays of Light are moved or mixed: But to those 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 of 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, are often deyed with several Colours: so the tops of Sorrel Roots will turn Red, those of Mullen, Turneps and Radishes, 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 more 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 this Colour, is the action 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 ascends by the Aer-Vessels, 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 transversly, 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; scil. 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 the other Parts continuing of a Redish 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 Causes of its Verdure.

11. §. BUT how doth the Aer concur to the Greeness of Plants? I answer; 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 substrata, 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 Prædominant 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 Plant; 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 Batchelors 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 besides 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 Lymphæducts 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 Lymphæducts with respect to the Aer-Vessels is greater in the Flower than in the Leaf.

20. §. It seemeth therefore, that the Aer-Vessels, and therefore the Aer, being predominant in the Leaf; Green, is therein also the predominant 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 Lymphæducts, 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 Lymphæducts 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; sc. 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 Bugloss turn Blew. So likewise the Purple of Bilberries, and the Crimson of 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.

23. §. 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 sort; 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 upon the Saline Principles: and that the Flower hath a different Figure from that of the Leaf: it follows, that there is some Saline Principle in the one, which is not in the other, especially, all in such Flowers, whose Figures are cut out by a greater Variety and Complication of Lines. The Leavs therefore, though variously shaped, yet agreeing so far in one common Figure, as usualy to be flat; it therefore seemeth plain, that there is a Saline Principle in them all, so far one, as to be the chief Cause of that common Figure: and in concurrence with the ambient Aer, to be likewise the chief Cause of one common Colour, sc. a Green.

25. §. Whereas the Figure of the Flowers, and therefore their Saline Principle, being more various, and commonly distinct from that of the Leaf; it will easily concur with as a great Variety of Salts in the Aer, whether Acid, Alkaline, Nitrous, Urinous, Armoniacal, or any other therein existent, to the Precipitation of the Sulphur into the like Variety of Colours. Thus far of the Colours of Plants as they appear in their Natural Estate.