Part 3

LEAVES are the Parts or Bowels of a Plant, which perform the same Office to Sap, as the Lungs of an Animal do to Blood; that is, they purify or cleanse it of the Recrements, or fuliginous Steams, received in the Circulation, being the unfit Parts of the Food; and perhaps some decay’d Particles, which fly off the Vessels, through which Blood and Sap do pass respectively.

Besides which Use, the Nitro-aerous Particles may there enter, to keep up the vital Ferment or Flame.

Mr. _Papin_ shews, that Air will pass in at the Leaves, and out thro’ the Plant at the Roots, but Water will not pass in at the Leaves; and that if the Leaves have no Air, a Plant will die; but if the Leaves have Air, tho’ the Root remain in Water _in vacuo_, the Plant will live and grow.

Dr. _Grew_, in his Anatomy of Plants, mentions Vessels, which he calls, Net-work, Cobweb, Skeins of Silk, _&c._ but above all, the Multitude of Air-Bladders in them, which I take to be of the same Use in Leaves, as the Vesiculæ are in Lungs. Leaves being as Lungs inverted, and of a broad and thin Form; their Vesiculæ are in Contact with the free open Air, and therefore have no need of Trachea, or Bronchia, nor of Respiration.

CHAP. II.

_Of_ FOOD _of_ PLANTS.

The chief Art of an Husbandman is to feed Plants to the best Advantage; but how shall he do that, unless he knows what is their Food? By Food is meant that Matter, which, being added and united to the first _Stamina_ of Plants, or _Plantulæ_, which were made in little at the Creation, gives them, or rather is their Increase.

’Tis agreed, that all the following Materials contribute, in some manner, to the Increase of Plants; but ’tis disputed which of them is that very Increase or Food. 1. _Nitre_. 2. _Water_. 3. _Air_. 4. _Fire_. 5. _Earth_.

I will not mention, as a Food, that acid Spirit of the Air, so much talk’d of; since by its eating asunder Iron Bars it appears too much of the Nature of _Aqua Fortis_, to be a welcome Guest alone to the tender Vessels of the Roots of Plants.

_Nitre_ is useful to divide and prepare the Food, and may be said to nourish Vegetables in much the same Manner as my Knife nourishes me, by cutting and dividing my Meat: But when _Nitre_ is apply’d to the Root of a Plant, it will kill it as certainly as a Knife misapply’d will kill a Man: Which proves, that _Nitre_ is, in respect of Nourishment, just as much the Food of Plants, as _White Arsenick_ is the Food of Rats. And the same may be said of Salts.

_Water_, from _Van-Helmont_’s Experiment, was by some great Philosophers thought to be it. But these were deceived, in not observing, that Water has always in its Intervals a Charge of Earth, from which no Art can free it. This Hypothesis having been fully confuted by Dr. _Woodward_, no body has, that I know of, maintain’d it since: And to the Doctor’s Arguments I shall add more in the Article of Air.

_Air_, because its Spring, _&c._ is as necessary to the Life of Vegetables, as the Vehicle of Water is; some modern Virtuosi have affirm’d, from the same and worse Arguments than those of the Water-Philosophers, that Air is the Food of Plants. Mr. _Bradley_ being the chief, if not only Author, who has publish’d this Phantasy, which at present seems to get Ground, ’tis fit he should be answer’d: And this will be easily done, if I can shew, that he has answer’d this his own Opinion, by some or all of his own Arguments.

His first is, that of _Helmont_, and is thus related in Mr. _Bradley_’s general Treatise of _Husbandry and Gardening_, Vol. I. _p._ 36. ‘Who dry’d Two hundred Pounds of Earth, and planted a Willow of Five Pounds Weight in it, which he water’d with Rain, or distill’d Water; and to secure it from any other Earth getting in, he covered it with a perforated Tin Cover. Five Years after, weighing the Tree, with all the Leaves it had borne in that Time, he found it to weigh One hundred Sixty-nine Pounds Three Ounces; but the Earth was only diminish’d about two Ounces in its Weight.’

On this Experiment Mr. _Bradley_ grounds his Airy Hypothesis. But let it be but examined fairly, and see what may be thence inferr’d.

The Tin Cover was to prevent any other Earth from getting in. This must also prevent any Earth from getting out, except what enter’d the Roots, and by them pass’d into the Tree.

A Willow is a very thirsty Tree, and must have drank in Five Years time several Tuns of Water, which must necessarily carry in its Interstices a great Quantity of Earth (probably many times more than the Tree’s[5] Weight, which could not get out, but by the Roots of the Willow.

[5] The Body of an Animal receives a much less Increase in Weight than its Perspirations amount to, as _Sanctorius_’s _Static-Chair_ demonstrates.

Therefore the Two hundred Pounds of Earth not being increased, proves that so much Earth as was poured in with the Water, did enter the Tree.

Whether the Earth did enter to nourish the Tree, or whether only in order to pass through it (by way of Vehicle to the Air), and leave the Air behind for the Augment of the Willow, may appear by examining the Matter of which the Tree did consist.

If the Matter remaining after the Corruption or Putrefaction of the Tree be Earth, will it not be a Proof, that the Earth remained in it, to nourish and augment it? for it could not leave what it did not first take, nor be augmented by what pass’d through it. According to _Aristotle_’s Doctrine, and Mr. _Bradley_’s too, in Vol. I. _pag._ 72. “Putrefaction resolves it again into Earth, its first Principle.”

The Weight of the Tree, even when green, must consist of Earth and Water. Air could be no Part of it, because Air being of no greater specific Gravity than the incumbent Atmosphere, could not be of any Weight in it; therefore was no Part of the One hundred Sixty-nine Pounds Three Ounces.

Nature has directed Animals and Vegetables to seek what is most necessary to them. At the Time when the _Fœtus_ has a Necessity of Respiration, ’tis brought forth into the open Air, and then the Lungs are filled with Air. As soon as a Calf, Lamb, _&c._ is able to stand, it applies to the Teat for Food, without any Teaching. In like manner Mr. _Bradley_ remarks, in his Vol. I. _pag._ 10. ‘That almost every Stem and every Root are formed in a bending manner under Ground; and yet all these Stems become strait and upright when they come above-ground, and meet the Air; and most Roots run as directly downwards, and shun the Air as much as possible.’

Can any thing more plainly shew the Intent of Nature, than this his Remark does? _viz._ That the Air is most necessary to the Tree above ground, to purify the Sap by the Leaves, as the Blood of Animals is depurated by their Lungs: And that Roots seek the Earth for their Food, and shun the Air, which would dry up and destroy them.

No one Truth can possibly contradict or interfere with any other Truth; but one Error may contradict and interfere with another Error, _viz._

Mr. _Bradley_, and all Authors, I think, are of Opinion, that Plants of different Natures are fed by a different Sort of Nourishment; from whence they aver, that a Crop of Wheat takes up all that is peculiar to that Grain; then a Crop of Barley all that is proper to it; next a Crop of Pease, and so on, ’till each has drawn off all those Particles which are proper to it; and then no more of these Grains will grow in that Land, till by Fallow, Dung, and Influences of the Heavens, the Earth will be again replenish’d with new Nourishment, to supply the same Sorts of Corn over again. This, if true (as they all affirm it to be), would prove, that the Air is not the Food of Vegetables. For the Air being in itself so homogeneous as it is, could never afford such different Matter as they imagine; neither is it probable, that the Air should afford the Wheat Nourishment more one Year, than the ensuing Year; or that the same Year it should nourish Barley in one Field, Wheat in another, Pease in a Third; but that if Barley were sown in the Third, Wheat in the First, Pease in the Second, all would fail: Therefore this Hypothesis of Air for Food interferes with, and contradicts this Doctrine of Necessity of changing Sorts.

I suppose, by Air, they do not mean dry Particles of Earth, and the Effluvia which float in the Air: The Quantity of these is too small to augment Vegetables to that Bulk they arrive at. By that way of speaking they might more truly affirm this of Water, because it must be like to carry a greater Quantity of Earth than Air doth, in proportion to the Difference of their different specific Weight; Water, being about 800 times heavier than Air, is likely to have 800 times more of that terrestrial Matter in it; and we see this is sufficient to maintain some Sort of Vegetables, as Aquatics; but the Air, by its Charge of Effluvia, _&c._ is never able to maintain or nourish any Plant; for as to the Sedums, Aloes, and all others, that are supposed to grow suspended in the Air, ’tis a mere Fallacy; they seem to grow, but do not; since they constantly grow lighter; and tho’ their Vessels may be somewhat distended by the Ferment of their own Juices which they received in the Earth, yet suspended in Air, they continually diminish in Weight (which is the true Argument of a Plant) until they grow to nothing. So that this Instance of Sedums, _&c._ which they pretend to bring for Proof of this their Hypothesis, is alone a full Confutation of it.

Yet if granted, that Air could nourish some Vegetables by the earthy Effluvia, _&c._ which it carry’d with it [6]; even that would be against them, not for them.

[6] This is meant of dry Earth, by its Lightness (when pulveriz’d extremely fine) carried in the Air without Vapour: For the Atmosphere, consisting of all the Elements, has Earth in it in considerable Quantity, mix’d with Water; but a very little Earth is so minutely divided, as to fly therein pure from Water, which is its Vehicle there for the most Part.

They might as well believe, that _Martins_ and _Swallows_ are nourish’d by the Air, because they live on Flies and Gnats, which they catch therein; this being the same Food, which is found in the Stomach of the Chameleon.

If, as they say, the Earth is of little other Use to Plants, but to keep them fix’d and steady, there would be little or no Difference in the Value of rich and poor Land, dung’d or undung’d; for one would serve to keep Plants fix’d and steady, very near, if not quite as well as the other.

If Water or Air was the Food of Plants, I cannot see what Necessity there should be of Dung or Tillage.

4. _Fire_. No Plant can live without Heat, tho’ different Degrees of it be necessary to different Sorts of Plants. Some are almost able to keep Company with the _Salamander_, and do live in the hottest Exposures of the hot Countries. Others have their Abode with Fishes under Water, in cold Climates: for the Sun has his Influence, tho’ weaker, upon the Earth cover’d with Water, at a considerable Depth; which appears by the Effect the Vicissitudes of Winter and Summer have upon subterraqueous Vegetables.

Tho’ every Heat is said to be a different Degree of Fire; yet we may distinguish the Degrees by their different Effects. Heat warms; but Fire burns: The first helps to cherish, the latter destroys Plants.

5. _Earth_. That which nourishes and augments a Plant is the true Food of it.

Every Plant is Earth, and the Growth and true Increase of a Plant is the Addition of more Earth.

_Nitre_ (or other Salts) prepares the Earth, Water and Air move it, by conveying and fermenting it in the Juices; and this Motion is called Heat.

When this additional Earth is assimilated to the Plant, it becomes an absolute Part of it.

Suppose Water, Air, and Heat, could be taken away, would it not remain to be a Plant, tho’ a dead one?

But suppose the Earth of it taken away, what would then become of the Plant? Mr. _Bradley_ might look long enough after it, before he found it in the Air among his specific or certain Qualities.

Besides, too much _Nitre_ (or other Salts) corrodes a Plant; too much Water drowns it; too much Air dries the Roots of it; too much Heat (or Fire) burns it; but too much Earth a Plant never can have, unless it be therein wholly buried; and in that Case it would be equally misapply’d to the Body, as Air or Nitre would be to the Roots.

Too much Earth, or too fine, can never possibly be given to Roots; for they never receive so much of it as to surfeit the Plants, unless it be depriv’d of Leaves, which, as Lungs, should purify it.

And Earth is so surely the Food of all Plants, that with the proper Share of the other Elements, which each Species of Plants requires, I do not find but that any common Earth will nourish any Plant.

The only Difference of Soil[7] (except the Richness) seems to be the different Heat and Moisture it has; for if those be rightly adjusted, any Soil will nourish any Sort of Plant; for let _Thyme_ and _Rushes_ change Places, and both will die; but let them change their Soil, by removing the Earth wherein the _Thyme_ grew, from the dry Hill down into the watry Bottom, and plant _Rushes_ therein; and carry the moist Earth, wherein the _Rushes_ grew, up to the Hill; and there _Thyme_ will grow in the Earth that was taken from the _Rushes_; and so will the _Rushes_ grow in the Earth that was taken from the _Thyme_; so that ’tis only more or less Water that makes the same Earth fit either for the Growth of _Thyme_ or _Rushes_.

[7] As I have said in my _Essay_, That _a Soil being once proper to a Species of Vegetables, it will always continue to be so_; it must be supposed, that there be no Alteration of the _Heat_ and _Moisture_ of it; and that this Difference I mean, is of its Quality of nourishing different Species of Vegetables, not of the Quantity of it; which Quantity may be alter’d by Diminution or Superinduction.

So for Heat; our Earth, when it has in the Stove the just Degree of Heat that each Sort of Plants requires, will maintain Plants brought from both the _Indies_.

Plants differ as much from one another in the Degrees of Heat and Moisture they require, as a Fish differs from a Salamander.

Indeed _Misletoe_, and some other Plants, will not live upon Earth, until it be first alter’d by the Vessels of another Plant or Tree, upon which they grow, and therein are as nice in Food as an Animal.

There is no need to have Recourse to Transmutation; for whether Air or Water, or both, are transform’d into Earth or not, the thing is the same, if it be Earth when the Roots take it; and we are convinced that neither Air nor Water alone, as such, will maintain Plants.

These kind of Metamorphoses may properly enough be consider’d in Dissertations purely concerning Matter, and to discover what the component Particles of Earth are; but not at all necessary to be known, in relation to the maintaining of Vegetables.

CHAP. III.

_Of_ PASTURE _of_ PLANTS.

Cattle feed on Vegetables that grow upon the Earth’s external Surface; but Vegetables themselves first receive, from within the Earth, the Nourishment they give to Animals.

The Pasture of Cattle has been known and understood in all Ages of the World, it being liable to Inspection; but the Pasture of Plants, being out of the Observation of the Senses, is only to be known by Disquisitions of Reason; and has (for ought I can find) pass’d undiscover’d by the Writers of Husbandry[8].

[8] When Writers of Husbandry, in discoursing of Earth and Vegetation, come nearest to the Thing, that is, the _Pasture_ of _Plants_, they are lost in the Shadow of it, and wander in a Wilderness of obscure Expressions, such as _Magnetism, Virtue, Power, Specific Quality, Certain Quality_, and the like; wherein there is no manner of Light for discovering the real Substance, but we are left by them more in the Dark to find it, than Roots are when they feed on it: And when a Man, no less sagacious than Mr. _Evelyn_, has trac’d it thro’ all the _Mazes_ of the _Occult Qualities_, and even up to the _Metaphysics_, he declares he cannot determine, whether the Thing he pursues be _Corporeal_ or _Spiritual_.

The Ignorance of this seems to be one principal Cause, that Agriculture, the most necessary of all Arts, has been treated of by Authors more superficially than any other Art whatever. The Food or _Pabulum_ of Plants being prov’d to be Earth, where and whence[9] they take that, may properly be called their Pasture.

[9] By the _Pasture_ is not meant the _Pabulum_ itself; but the _Superficies_ from whence the _Pabulum_ is taken by Roots.

This Pasture I shall endeavour to describe.

’Tis the inner or (internal) Superficies[10] of the Earth; or which is the same thing, ’tis the Superficies of the Pores, Cavities, or Interstices of the divided Parts of the Earth, which are of two Sorts, viz. _Natural_ and _Artificial_.

[10] This Pasture of Plants never having been mentioned or described by any Author that I know of, I am at a loss to find any other Term to describe it by, that may be synonymous, or equipollent to it: Therefore, for want of a better, I call it the inner, or internal Superficies of the Earth, to distinguish it from the outer or external Superficies, or Surface, whereon we tread.

Inner or internal Superficies may be thought an absurd Expression, the Adjective expressing something within, and the Substantive seeming to express only what is without it; and indeed the Sense of the Expression is so; for the Vegetable Pasture is within the Earth, but without (or on the Outsides of) the divided Parts of the Earth.

And, besides, Superficies must be joined with the Adjective Inner (or Internal) when ’tis used to describe the Inside of a thing that is hollow, as the Pores and Interstices of the Earth are.

The Superficies, which is the Pasture of Plants, is not a bare Mathematical Superficies; for that is only imaginary.

By Nature, the whole Earth (or Soil) is composed of Parts; and, if these had been in every Place absolutely joined, it would have been without Interstices or Pores, and would have had no internal Superficies, or Pasture for Plants: but since it is not so strictly dense[11], there must be Interstices at all those Places where the Parts remain separate and divided.

[11] For were the Soil as dense as Glass, the Roots or Vegetables (such as our Earth produces) would never be able to enter its Pores.

These Interstices, by their Number and Largeness, determine the specific Gravity (or true Quantity) of every Soil: The larger they are, the lighter is the Soil; and the inner Superficies is commonly the less.

The Mouths, or Lacteals, being situate, and opening, in the convex Superficies of Roots, they take their _Pabulum_, being fine Particles of Earth, from the Superficies of the Pores, or Cavities, wherein the Roots are included.

And ’tis certain, that the Earth is not divested or robb’d of this _Pabulum_, by any other Means, than by actual Fire, or the Roots of Plants.

For, when no Vegetables are suffer’d to grow in a Soil, it will always grow richer. Plow it, harrow it, as often as you please, expose it to the Sun in Horse-Paths all the Summer, and to the Frost of the Winter; let it be cover’d by Water at the Bottom of Ponds, or Ditches; or if you grind dry Earth to Powder, the longer ’tis kept exposed, or treated by these or any other Method possible (except actual Burning by Fire); instead of losing, it will gain the more Fertility.

These Particles, which are the _Pabulum_ of Plants, are so very minute[12] and light, as not to be singly attracted to the Earth, if separated from those Parts to which they adhere[13], or with which they are in Contact (like Dust to a Looking-Glass, turn it upwards, or downwards, it will remain affixt to it), as these Particles do to those Parts, until from thence remov’d by some Agent.

[12] As to the Fineness of the _Pabulum_ of Plants, ’tis not unlikely, that Roots may insume no grosser Particles, than those on which the Colours of Bodies depend; but to discover the greatest of those Corpuscles, Sir _Isaac Newton_ thinks, it will require a Microscope, that with sufficient Distinctness can represent Objects Five or Six hundred times bigger, than at a Foot Distance they appear to the naked Eye.

My Microscope indeed is but a very ordinary one, and when I view with it the Liquor newly imbibed by a fibrous Root of a Mint, it seems more limpid than the clearest common Water, nothing at all appearing in it.

[13] Either Roots must insume the Earth, that is their _Pabulum_, as they find it in whole Pieces, having intire Superficies of their own, or else such Particles as have not intire Superficies of their own, but want some Part of it, which adheres to, or is Part of the Superficies of larger Particles, before they are separated by Roots. The former they cannot insume (unless contained in Water); because they would fly away at the first Pores that were open: _Ergo_ they must insume the latter.

A Plant cannot separate these Particles from the Parts to which they adhere, without the Assistance of Water, which helps to loosen them.

And ’tis also probable, that the Nitre of the Air may be necessary to relax this Superficies, to render the prolific Particles capable of being thence disjoin’d; and this Action of the Nitre seems to be what is call’d, Impregnating the Earth.

Since the grosser Vegetable Particles, when they have pass’d thro’ a Plant, together with their moist Vehicle, do fly up into the Air invisibly; ’tis not likely they should, in the Earth, fall off from the Superficies of the Pores, by their own Gravity: And if they did fall off, they might fly away as easily before they enter’d Plants, as they do after they have pass’d thro’ them; and then a Soil might become the poorer[14] for all the Culture and Stirring we bestow upon it; tho’ no Plants were in it; contrary to Experience.

[14] But we see it is always the richer by being frequently turned and exposed to the Atmosphere: Therefore Plants must take all their _Pabulum_ from a Superficies of Parts of Earth; except what may perhaps be contained in Water fine enough to enter Roots intire with the Water.