_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.