Part 42

This is most certain, that unless we can keep our Luserne pretty clean from natural Grass, we cannot expect it to succeed, let the Soil be never so proper.

CHAP. XIV.

Of Change of SPECIES.

I. That Plants of the most different Nature feed on the same Sort of Food.

II. That there is no Plant but what must rob any other Plant within its Reach.

III. That a Soil which is proper to one Sort of Vegetable once, is, in Respect of the Sort of Food it gives, proper to it always.

If any one of these Three Propositions be true, as I hope to prove all of them are, then it will follow, that there is no need to change the Species of Vegetables from one Year to another, in respect to the different Food the same Soil is, tho’ falsely, supposed to yield.

For if all Plants rob one another, it must be because they all feed on the same Sort of Food; and, admitting they do, there can be no Necessity of changing the Species of them, from one Soil to another; but the same Quantity of the same Food, with the same Heat and Moisture which maintains any Species one Year, must do it any other Year.

The common Opinion is contrary to all these (as it must be, if contrary to any one of them): And since an Error in this fundamental Principle of Vegetation is of very ill Consequence; and since Dr. Woodward, who has been serviceable in other respects to this Art, has unhappily fallen in with the Vulgar in this Point; his Arguments for this Error require to be answer’d in the first Place.

By proving, in his Experiments, that Earth is the Pabulum of Plants.

The Doctor says ‘It is not possible to imagine how one uniform, homogeneous Matter, having its Principles, or original Parts, all of the same Substance, Constitution, Magnitude, Figure, and Gravity, should ever constitute Bodies so egregiously unlike, in all those Respects, as Vegetables of different Kinds are; nay, even as the different Parts of the same Vegetable.’

In Philos. Trans. No. 253.

‘That there should be that vast Difference in them, in their several Constitutions, Makes, Properties, and Effects, and yet all arise from the very same Sort of Matter, would be very strange.’

Answer. ’Tis very probable, that the terrestrial Particles which constitute Vegetables, tho’ inconceivably minute, may be of great Variety of Figure, and other Differences; else they could not be capable of the several Ferments, &c. they must undergo in the Vessels of Plants. Their Smalness can be no Objection to their Variety, since even the Particles of Light are of various Kinds.

But as the Doctor asserts, ‘That each Part of the same Vegetable requires a peculiar specific Matter for its Formation and Nourishment; and that there are very many and different Ingredients to go to the Composition of the same individual Plants;’

From hence must be inferred, that the same Plant takes in very many and different Ingredients (and it is proved, that no Plant refuses any Ingredient that is capable of entering its Roots. Tho’ the terrestrial Particles which nourish Vegetables, be not perfectly homogeneous; yet most of the various Tastes and Flavours of Plants are made in and by the Vessels.

Dr. Grew, in his Anatomy of Plants, by microscopical Inspection, found, that the outer Superficies of Roots was of a spongy Substance; and ’tis well known, that no such Body can refuse to imbibe whatever Liquor comes in Contact with it, but will by its springy Porosity absorb any sort of Moisture.

We are convinced, that ’tis the Vessels of Plants that make the different Flavours; because there is none of these Flavours in the Earth of which they are made, until that has enter’d and been alter’d by the vegetable Vessels.

Doctor Woodward says, ‘That Water will pass Pores and Interstices, that neither Air, nor any other Fluid, will: This enables it to enter the finest Tubes and Vessels of Plants, and to introduce the terrestrial Matter, conveying it to all Parts of them; whilst each, by means of Organs ’tis endow’d with for the Purpose, intercepts, and assumes into itself, such Particles as are suitable to its own Nature; letting the rest pass on through the common Ducts.’

If the Doctor’s Plants were so nice in leaving vegetable Matter behind, quiet and undisturb’d, ’tis a Wonder they would take up the mineral Matter, as, he says, they did, that kill’d themselves with Nitre.

These Plants might, with much less Difficulty, have distinguish’d the mineral Matter from the vegetable Matter, than they could distinguish the different Particles of vegetable Matter from one another, and must have been very unwise to chuse out the Nitre (their Poison) from the Water and Earth, and to leave the vegetable Particles behind; none of which could be so improper to them as the Nitre.

It may perhaps be objected, that such like pernicious Matter kills a Plant by only destroying its Roots, and by closing the Pores; which prevents the Nourishment from entering to maintain its Life; and that such Matter doth not itself enter to act as Poison upon the Sap, or upon the Vessels of the Body, or Leaves: But it plainly appears that it doth enter, and act as Poison; for when some of the Roots of a Mint, growing in Water, are put into salt Water, it kills the whole Plant, although the rest of the Roots remaining in the fresh Water were sufficient to maintain it, if the other Roots had been cut off at the Time they were removed into the Salt Water; and also all the Leaves, when dead, will be full of Salt.

Or if the Juice of wild Garlick-seed be made use of instead of the salt Water, it will have the same Effect; and every one of the Mint-leaves will have a strong Taste of Garlick in it.

Here then he says plainly, That each Plant receives the terrestrial Matter in gross, both suitable and unsuitable to its Nature, retains the suitable Particles for its Augment, and the unsuitable lets pass through it. And in another Place he says they are exhal’d into the Atmosphere.

And this will appear to be the true Case of Plants; and directly contradicts what he advances, in saying, ‘That each Sort of Grain takes forth that peculiar Matter that is proper for its own Nourishment. First, the Wheat draws off those Particles that suit the Body of that Plant, the rest lying all quiet and undisturb’d the while. And when the Earth has yielded up all them, those that are proper for Barley, a different Grain, remain still behind, till the successive Crops of that Corn fetch them forth too; and so the Oats and Pease in their turn, till, in fine, all is carried off.’

In the former Paragraph he says, each Plant lets pass through it the rest of the Particles that are not suitable to its own Nature. In the latter Paragraph he says, That each leaves the unsuitable all behind for another Sort; and so on.

Both cannot be true.

If the latter were true, Change of Sorts would be as necessary as it is commonly thought. But if the former be true, as I hope to prove it is, then there can be no Use of changing of Sorts in Respect of different Nourishment.