CHAP. VI.
Of the Manner of the Generation of the Leaf. Where also, that of the Two General Parts of a Plant, sc. the Lignous and Parenchymous, is further explain’d.
HE Visible Causes of the Figures of Leaves, have been formerly mentioned. B. 1. Ch. 4. It may here be further noted, That the greater Fibers of the Leaf, being never Braced in the Stalk; it is a good preparative for their better spreading in the Leaf. As also, that the same is much favour’d, by the extream smalness of the Aer-Vessels herein: whereby they are more easily divaricated, in the lesser Fibers, and so the Leaf dilated.
2. §. BUT these and the like are to be reckoned a secondary Order of Causes; which serve rather to carry on and improve, that which Nature hath once begun. Idea, §. 53. And therefore, we must not only consider the visible Mechanism of the Parts; but also the Principles of which they are composed; wherewith, Nature seems to draw her first Strokes.
3. §. Now of these, I have formerly, and as I conceive upon good ground, supposed, the chief Governing Principle, to be the Saline, whether Alkaline, Acid, or of any other Kind: Lib. 2. P. 2. §. 31, &c. being in some sort as the Mold of a Button, to which the other Principles, as its Attire, do all conform. Or the Salts are, as it were, the Bones; the other Principles, as the Flesh which covers them.
4. §. A further Argument hereof may be deduced from the Cuticular and other Concretions, commonly called Mothers, in Distill’d Waters, Vinegar, and other Liquors. For in these Concretions, there is always a tendence to Vegetation; and many of them are true Vegetables in their Kind; as shall hereafter be seen. Now the Liquors, in which these are generated, do always, wholly or in part, lose their Tast and Smell, and so become Vapid. The more sensible Principles therein having made their Transit from the Fluid, into the Concrete Parts. So, I have known, sometimes, Vinegar it self, to become by these Concretions, almost as Tastless as Common Water. Whereby it seems evident, That of Vegetable Principles, there are some, more Masterly than others: and that of these, the Saline is the chief. The same is likewise argued, from the frequent Experiment of many good Husband-men; that most Bodies which abound with Salt, are the greatest Nourishers of Plants.
5. §. This Saline Principle, as is above hinted, is to be understood, a Generik Name, under which divers Species are comprehended; and of some whereof, it is always compounded, as in other Bodies, so in Plants. As shall be made to appear, by divers Experiments, when we come, hereafter, to speak of Vegetable Salts. Whereby we are conducted, yet further to enquire, What are the Principles of this Principle?
6. §. NOW these seem to be Four; a Nitrous, an Acid, an Alkaline, and a Marine. The Admixture of the First, is argu’d from the Place, which Nature hath assigned for the Generation and Growth of most Plants, sc. neither in Caverns under Ground, as for Minerals; nor above it, as for Animals; but the Surface of the Earth, where this Sort of Salt is copiously bred. And doth therefore prove, not only a Mixture, but a good Proportion hereof with the other Principles of a Plant. Hence it is, that Dew or Water on Windows or Plain and Smooth Tables, by virtue of a Nitro-Aerial Salt, is often frozen into the resemblance of little Shrubs. And the like Figure I have often seen in a well filtred Solution of the Salt of any of our Purging Waters, as of Epsom, &c. being set to shoot. Produced, as I conceive, by the Nitre, which with the Rain or other Waters, is washed down from the Surface of the Earth, and so mixed with the Mineral Salts.
7. §. The other Three Salts are exhibited, by the several ways of Resolving the Principles of a Plant. Many Plants, even in their Natural Estate, do yield an Acid Juyce. And the Juyces of many more, by Fermentation, will become Acid. And most, by Distillation in a Sand-Furnace, yield an Acid Liquor.
8. §. By Calcination, all Sorts of Plants, yield more or less, both of a Fixed and a Volatile Alkaly: the former, in the Ashes; the latter, in the Soot. And, at least the generality, by Fermentation also, yield a Volatile one; or such a kind of Salt, which, whether we call an Urinous, or otherwise, hath the like Odour and Tast with that of Urine, Harts-Horn, Soot, and the like.
9. §. The Marine, is obtained no other way, that I know of, but from a Solution of the Alkaline, upon its being exposed to the Aer. The process wherof, I shall particularly set down in a following Discourse. Of these Salts, mixed in a certain proportion, together, and also Impregnated with some of the other Active Principles of a Plant, and not without an Admixture of some Parts from the Aer; I suppose, that which I call the Essential, is produced: of which, I shall also give an account in the same Discourse.
10. §. ALL THE Four Salts above mentioned, seem in their Order, to have a share in the Formation of a Leaf, or other Part of a Plant: And first of all, the Marine. For all Generations are made in some Fluid: But in every Fluid there is a perpetual Intestive Motion of Parts. So that the first Intention of Nature is, That some of those Parts be disposed to Rest. Now of all the Principles of a Plant, there are none hereunto more disposed, than their Salts; whose Particles, being figu’rd with plain Sides, as often as they touch Side to Side, like two Marbles exquisitely polished, they will adhere together. And the Particles of Marine Salt, being Cubick; and so, with respect to their Figure, of greater Bulk than those of any other Salt; they will hereby, be most and first of all disposed to Rest; and so become, as it were, the Foundation of the following Superstructure.
11. §. THE Second Intention of Nature is, That the Particles be brought to Rest, in a certain Position, agreeable to the Figure of the Parts which are to be formed. And therefore in the next place, all those Parts of a Plant which are truly Lignous, by the Marine Salt, with the assistance of the Alkaline, but especially of the Nitrous, are made to shoot out in Length, or into an innumerable company of small Cylindrick Fibres: Tab. 53. these Salts being, altogether, sturdy enough to resist those Impulses which might incline them to conform to any other Figure.
12. §. THE next Intention is, That these Fibres, at the same time in which they are formed, may likewise receive such a Posture as will best answer the indented Shape of the Leaf. Which Posture, although in the Growth of the Leaf it is much Govern’d by the Aer-Vessels; yet in the Generation hereof, seems to be first determined by the forementioned Salts, according to their several Angles, whereby they are differently applicable one to another.
13. §. Now all the Sides of the Marine Salt, and the Sides and the Ends of the Nitrous, properly so called, stand at Right Angles. And it is very probable, from the Figure of the Crystalls in Spirit of Blood, and some other Bodies, that the Particles of the Alkaline are Square at one End, and Poynted at the other. Tab. 53. And those of the Acid, at both; And that, withal, they are Shorter and more Slender.
14. §. It should therefore seem, That where the Alkaline Salt is any way predominant, and that the Particles thereof are placed End to End; there the Lignous Fibres (as the larger ones in many Leaves) Tab. 53. declining their parallel Growth, begin to shoot out obliquely, or at Angles one with another, and those Acute.
15. §. If the same Salt be predominant, and some of its Particles placed, with the Pointed End of one, to the Side of another, Tab. 53. or the Square End of one, to the Poynted End of another; there the said Fibres begin to shoot at Angles less Acute.
16. §. But if either the Marine or Nitrous Salt is predominant; or some Particles of the Alkaline, are placed with the Square End of one, to the Side of another; Tab. 53. there the Fibres begin to make, not Acute, but Right Angles; as do the greater Fibres, in some Leaves; and the smaller, in all.
17. §. IN the same manner, the Fibre in the Circumference of the Leaf is also governed; the Particles of the said Salt, being reduceable, not only to any Angle, but also to any Circle, or other Crooked Line, as they are variously applyed. For if the major part be applied End to End, and only every Third or Fourth applied End to Side, they produce a great Circle. Tab. 53. But if the Poynted End of each, be set to the Side of another, they make a less. And if the Application be the same, but to the contrary Side, they thence begin a new Circle with the same Diameter, but with another Center, answerable to the intended Shape of the Leaf.
18. §. AFTER the same manner, the Aer-Vessels may be formed by the Particles of the Acid Salt. Which, without being supposed to be crooked (as those of the Aer, at least the compounded ones, probably be) only by applying the lesser Side of one, to the greater Side of another, will also be reduced to any either Circular or Spiral Line. Tab. 53. And so, likewise, for the production of the winding Fibres, which compose the Bladders of the Pith and other Parenchymous Parts of a Plant.
19. §. Thus doth Nature every where γεωμετρεῖν. For what She appears in Her Works, She must needs be also in their Causes.