_Of_ ROOTS _and_ LEAVES.
Since the most immediate Use of _Agriculture_, in feeding Plants,
relates to their _Roots_, they ought to be treated of in the first
Place.
_Roots_ are very different in different Plants: But ’tis not
necessary here to take notice of all the nice Distinctions of them;
therefore I shall only divide them in general into two Sorts, _viz._
_Horizontal-Roots_, and _Tap-Roots_, which may include them all.
All have Branchings and Fibres going all manner of ways, ready to fill
the Earth that is open.
But such _Roots_ as I call Horizontal (except of Trees) have seldom any
of their Branchings deeper than the Surface or Staple of the Earth,
that is commonly mov’d by the Plough or Spade.
The Tap-Root commonly runs down Single and Perpendicular[1] reaching
sometimes many Fathoms below.
[1] In this manner descends the first Root of every Seed; but of Corn
very little, if at all, deeper than the Earth is tilled.
These first Seed-Roots of Corn die as soon as the other Roots come
out near the Surface, above the Grain: and therefore this first is
not called a Tap Root; but yet some of the next Roots that come out
near the Surface of the Ground, always reach down to the Bottom of
the pulveriz’d Staple; as may be seen, if you carefully examine it
in the Spring time; but this first Root in Saint-foin becomes a Tap
Root.
This (tho’ it goes never so deep) has horizontal ones passing out all
round the Sides; and extend to several Yards Distance from it, after
they are by their Minuteness, and earthly Tincture, become invisible
to the naked Eye.
_A Method how to find the Distance to which_ Roots _extend
Horizontally._
_Pl._ 6. _Fig._ 7. Is a Piece or Plot dug and made fine in whole hard
Ground, the End _A_ 2 Feet, the End _B_ 12 Feet, the Length of the
Piece 20 Yards; the Figures in the middle of it are 20 _Turneps_, sown
early, and well ho’d.
The manner of this Hoing must be at first near the Plants, with a
Spade, and each time afterwards, a Foot farther Distance, till all the
Earth be once well dug; and if Weeds appear where it has been so dug,
hoe them out shallow with the Hand-Hoe. But dig all the Piece next the
out Lines deep every time, that it may be the finer for the _Roots_ to
enter, when they are permitted to come thither.
If these _Turneps_ are all gradually bigger, as they stand nearer to
the End _B_, ’tis a Proof they all extend to the Outside of the Piece;
and the _Turnep_ 20 will appear to draw Nourishment from six Feet
Distance from its Centre.
But if the _Turneps_ 16, 17, 18, 19, 20, acquire no greater Bulk than
the _Turnep_ 15, it will be clear, that their _Roots_ extend no farther
than those of the _Turnep_ 15 does; which is but about 4 Feet.
By this Method the Distance of the Extent of _Roots_ of any Plant may
be discover’d.
What put me upon this Method was an Observation of two Lands (or
Ridges) drill’d with _Turneps_ in Rows, a Foot asunder, and very even
in them; the Ground, at both Ends, and one Side, was hard and unplow’d;
the _Turneps_ not being ho’d, were very poor, small, and yellow, except
the Three outside Rows, _B_, _C_, _D_, which stood next to the Land (or
Ridge) _E_, which Land being plow’d and harrow’d, at the time the Land
_A_ ought to have been ho’d, gave a dark flourishing Colour to these
three Rows; and the _Turneps_ in the Row _D_, which stood farthest off
from the new-plow’d Land _E_, received so much Benefit from it, as to
grow twice as big as any of the more distant Rows. The Row _C_, being a
Foot nearer to the new-plow’d Land, became twice as large as those in
_D_; but the Row _B_, which was next to the Land _E_, grew much larger
yet[2].
[2] A like Observation to this on the Land E, has been made in
several Turnep Fields of divers Farmers, where Lands adjoining to
the Turneps have been well tilled; all the Turneps of the contiguous
Lands that were within three or four Feet, or more, of the newly
pulveriz’d Earth, received as great, or greater increase, in the
Manner as my Rows B C D did; and what is yet a greater Proof of the
Length of Roots, and of the Benefit of deep Hoing, all these Turneps
have been well Hand-ho’d; which is a good Reason why the Benefit of
the deep Pulveration should be perceivable at a greater Distance from
it than mine, because my Turneps, not being hoed at all, had not
Strength to send out their Roots through so many Feet of unpulveriz’d
Earth, as these can through their Earth pulveriz’d by the Hoe, tho’
but shallowly.
This Observation, as ’tis related to me (I being unable to go far
enough to see it myself) sufficiently demonstrates the mighty
Difference there is between Hand-hoing and Horse-hoing.
_F_ Plate 6. is a Piece of hard whole Ground, of about two Perch in
Length, and about two or three Feet broad, lying betwixt those two
Lands, which had not been plow’d that Year; ’twas remarkable, that
during the Length of this interjacent hard Ground, the Rows _B_, _C_,
_D_, were as small and yellow as any in the Land.
The _Turneps_ in the Row _D_, about three Feet distant from the Land
_E_, receiving a double Increase, proves they had as much Nourishment
from the Land _E_, as from the Land _A_, wherein they stood; which
Nourishment was brought by less than half the Number of _Roots_ of each
of these _Turneps_.
In their own Land they must have extended a Yard all round, else they
could not have reach’d the Land _E_, wherein ’tis probable these few
Roots went more than another Yard, to give each _Turnep_ as much
Increase as all the Roots had done in their own Land.
Except that it will hereafter appear, that the new Nourishment taken at
the Extremities of the Roots in the Land _E_, might enable the Plants
to send out more new Roots in their own Land, and receive something
more from thence.
The Row _C_ being twice as big as the Row _D_, must be suppos’d to
extend twice as far; and the Row _B_, four times as far, in proportion
as it was of a Bulk quadruple to the Row _D_.
A _Turnep_ has a Tap-Root, from whence all these Horizontal Roots are
deriv’d.
And ’tis observable; that betwixt these two Lands there was a Trench,
or Furrow, of about the Depth of nine or ten Inches, where these Roots
must descend first, and then ascend into the Land _E_: But it must be
noted, that some small Quantity of Earth was, by the Harrowing, fall’n
into this Furrow, else the Roots could not have pass’d thro’ it.
_Roots_ will follow the open Mould[3], by descending perpendicularly,
and mounting again in the same manner: As I have observ’d the Roots
of a Hedge to do, that have pass’d a steep Ditch two Feet deep, and
reach’d the Mould on the other side, and there fill it; and digging
Five Feet distant from the Ditch, found the Roots large, tho’ this
Mould was very shallow, and no Roots below the good Mould.
[3] A Chalk-Pit, contiguous to a Barn, the Area of which being about
40 Perch of Ground, was made clean and swept; so that there was not
the Appearance of any Part of a Vegetable, more than in the Barn’s
Floor: Straw was thrown from thence into the Pit, for Cattle to lie
on; the Dung made thereby was haled away about three Years after the
Pit had been cleansed; when, at the Bottom of it, and upon the Top of
the Chalk, the Pit was covered all over with Roots, which came from
a Witch-Elm, not more than Five or Six Yards in Length, from Top to
Bottom, and which was about Five Yards above, and Eleven Yards from
the Area of the Pit; so that in three Years the Roots of this Tree
extended themselves Eight times the Length of the Tree, beyond the
Extremities of the old Roots, at Eleven Yards Distance from the Body:
The annual-increased Length of the Roots was near Three times as much
as the Height of the Tree.
I’m told an Objection hath been made from hence against the Growth of
a Plant’s being in proportion to the Length of its Roots; but when
the Case is fully stated, the Objection may vanish. This Witch-Elm is
a very old decay’d Stump, which is here called a _Staggar_, appearing
by its Crookedness to have been formerly a _Plasher_ in an old
White-thorn Hedge wherein it stands: It had been lopped many Years
before that accidental Increase of Roots happened; it was stunted,
and sent out poor Shoots; but in the third Year of these Roots, its
Boughs being most of them horizontally inclined, were observed to
grow vigorously, and the Leaves were broad, and of a flourishing
Colour; at the End of the third Year all these Roots were taken away,
and the _Area_ being a Chalk-Rock lying uncovered, round the Place
where the Single Root, that produced all these, came out of the Bank,
no more Roots could run out on the bare Chalk, and the Growth of the
Boughs has been but little since.
_Wheat_, drill’d in double Rows in _November_, in a Field well till’d
before Planting, look’d yellow, when about Eighteen Inches high; at
Two Feet Distance from the Plants, the Earth was Ho-plow’d, which
gave such Nourishment to ’em, that they recovered their Health, and
changed their sickly Yellow, to a lively Green Colour.
So in an Orchard, where the Trees are planted too deep, below the
Staple or good Mould, the Roots, at a little Distance from the Stem,
are all as near the upper Superficies of the Ground, as of those Trees,
which are planted higher than the Level of the Earth’s Surface.
But the Damage of planting a Tree too low in moist Ground is, that in
passing thro’ this low Part, standing in Water, the Sap is chill’d, and
its Circulation thereby retarded.
One Cause of Peoples not suspecting Roots to extend to the Twentieth
Part of the Distance which in reality they do, was from observing these
Horizontal-Roots, near the Plant, to be pretty taper; and if they did
diminish on, in proportion to what they do there, they must soon come
to an End. But the Truth is, that after a few Inches, they are not
discernibly taper, but pass on to their Ends very nearly of the same
Bigness; this may be seen in _Roots_ growing in Water, and in some
other, tho’ with much Care and Difficulty.
In pulling up the aforemention’d _Turneps_, their Roots seem’d to end
at few Inches Distance from the Plants, they being, farther off, too
fine to be perceiv’d by ordinary Observation.
I found an extreme small Fibre on the Side of a _Carrot_, much less
than a Hair; but thro’ a Microscope it appear’d a large Root, not
taper, but broken off short at the End, which it is probable might have
(before broken off) extended near as far as the _Turnep_ Roots did.
It had many Fibres going out of it, and I have seen that a _Carrot_
will draw Nourishment from a great Distance, tho’ the Roots are almost
invisible, where they come out of the _Carrot_ itself.
By the Piece _F_ Plate 6. may be seen, that those Roots cannot
penetrate, unless the Land be open’d by Tillage, _&c._
As Animals of different Species have their Guts bearing different
Proportions to the Length of their Bodies; so ’tis probable, different
Species of Plants may have their Roots as different. But if those which
have shorter Roots have more in Number, and having set down the means
how to know the Length of them in the Earth, I leave the different
Lengths of different Species to be examin’d by those who will take the
Pains of more Trials. This is enough for me, that there is no Plant
commonly propagated, but what will send out its Roots far enough, to
have the Benefit of all the ho’d Spaces or Intervals I in the following
Chapters allot them, even tho’ they should not have Roots so long as
their Stalks or Stems.
And this great Length of Roots will appear very reasonable, if we
compare the Largeness of the Leaves (which are the Parts ordain’d for
Excretion) with the Smalness of the Capillary Roots, which must make
up in Length or Number what they want in Bigness, being destin’d to
range far in the Earth, to find out a Supply of Matter to maintain
the whole Plant; whereas the chief Office of the Stalks and Leaves is
only to receive the same, and to discharge into the Atmosphere such
Part thereof as is found unfit for Nutrition; a much easier Task than
the other, and consequently fewer Passages suffice, these ending in an
obtuse Form; for otherwise the Air would not be able to sustain the
Stalks and Leaves in their upright Posture: but the Roots, tho’ very
weak and slender, are easily supported by the Earth, notwithstanding
their Length, Smalness, and Flexibility.
Plants have no Stomach, nor _Oesophagus_, which are necessary to
convey the Mass of Food to an Animal: Which Mass, being exhausted by
the Lacteals, is eliminated by way of Excrements, but the Earth itself
being that Mass to the Guts (or Roots) of Plants, they have only fine
Recrements, which are thrown off by the Leaves.
In this, Animal and Vegetable Bodies agree, that Guts and Roots are
both injured by the open Air; and Nature has taken an equal Care, that
both may be supply’d with Nourishment, without being expos’d to it.
Guts are supply’d from their Insides, and Roots from their Outsides.
All the Nutriment (or _Pabulum_) which Guts receive for the Use of
an Animal, is brought to them; but Roots must search out and fetch
themselves all the _Pabulum_ of a Plant; therefore a greater Quantity
of Roots, in Length or Number, is necessary to a Plant, than of Guts to
an Animal.
All _Roots_ are as the Intestines of Animals, and have their Mouths or
Lacteal Vessels opening on their outer spongy Superficies, as the Guts
of Animals have theirs opening in their inner spongy Superficies.
The Animal Lacteals take in their Food by the Pressure that is made
from the Peristaltic Motion, and that Motion caus’d by the Action
of Respiration, both which Motions press the Mouths of the Lacteals
against the Mass or Soil which is within the Guts, and bring them into
closer Contact with it.
Both these Motions are supply’d in Roots by the Pressure occasion’d
by the Increase of their Diameters in the Earth, which presses their
Lacteal Mouths against the Soil without. But in such Roots as live in
Water, a Pressure is constantly made against the Roots by the Weight
and Fluidity of the Water; this presses such fine Particles of Earth it
contains, and which come into Contact with their Mouths, the closer to
them.
And when _Roots_ are in a till’d Soil, a great Pressure is made against
them by the Earth, which constantly subsides, and presses their Food
closer and closer, even into their Mouths; until itself becomes so hard
and close, that the weak Sorts of Roots can penetrate no farther into
it, unless re-open’d by new Tillage, which is call’d Hoing.
When a good Number of Single-Mint Stalks had stood in Water, until they
were well stock’d with Roots from their two lower Joints, and some of
them from three Joints, I set one in a Mint-Glass full of Salt Water;
this Mint became perfectly dead within three Days.
Another Mint I put into a Glass of fair Water; but I immers’d one
String of its Roots (being brought over the Top of that Glass into
another Glass of Salt-water, contiguous to the Top of the other Glass:
This _Mint_ dy’d also very soon.
Of another (standing in a Glass of Water and Earth till it grew
vigorously) I ty’d one single Root into a Bag, which held a Spoonful
of dry Salt, adjoining to the Top of the Glass, which kill’d this
strong Mint also. I found that this Salt was soon dissolv’d, tho’ on
the Outside of the Glass; and tho’ no Water reach’d so high, as to be
within Two Inches of the Joint which produc’d this Root: The Leaves of
all these were salt as Brine to the Taste.
Of another, I put an upper Root into a small Glass of Ink, instead of a
Bag of Salt, in the Manner above-mention’d; this Plant was also kill’d
by some of the Ink Ingredients. The Blackness was not communicated to
the Stalk, or Leaves, which inclin’d rather to a yellowish Colour as
they died, which seem’d owing to the _Copperas_.
I made a very strong Liquor with Water, and bruised Seeds of
_Wild-Garlick_, and, filling a Glass therewith, plac’d the Top of it
close to the Top of another Glass, having in it a Mint, two or three of
whose upper Roots, put into this stinking Liquor, full of the bruised
Seeds, and there remaining, it kill’d the Mint in some time; but it
was much longer in dying than the others were with Salt and Ink. It
might be, because these Roots in the _Garlick_ were very small, and did
not bear so great a Proportion to their whole System of Roots, as the
Roots, by which the other Mints were poison’d, did to theirs.
When the Edges of the Leaves began to change Colour, I chew’d many of
them in my Mouth, and found at first the strong aromatic Flavour of
Mint, but that was soon over; and then the nauseous Taste of _Garlick_
was very perceptible to my Palate.
I observ’d, that when the _Mint_ had stood in a Glass of Water, until
it seem’d to have finish’d its Growth, the Roots being about a Foot
long, and of an earthy Colour, after putting in some fine Earth, which
sunk down to the Bottom, there came from the upper Joint a new Set of
white Roots, taking their Course on the Outside of the Heap of old
Roots downwards, until they reach’d the Earth at the Bottom; and then,
after some time, came to be of the same earthy Colour with the old
ones.
Another _Mint_ being well rooted from Two Joints, about Four Inches
asunder; I plac’d the Roots of the lower Joint in a deep Mint-Glass,
having Water at the Bottom, and the Roots of the upper Joint into a
square Box, contriv’d for the Purpose, standing over the Glass, and
having a Bottom, that open’d in the Middle, with a Hole, that shut
together close to the Stalk, just below the upper Joint; then laying
all these upper Roots to one Corner of the Box, I fill’d it with Sand,
dry’d in a Fire-shovel, and found, that in one Night’s time, the Roots
of the lower Joint, which reach’d the Water at the Bottom of the Glass,
had drawn it up, and imparted so much thereof to those Roots in the Box
above, that the Sand, at that Corner where they lay, was very wet, and
the other three Corners dry. This Experiment I repeated very often, and
it always succeeded as that did.
And for the same Purpose I prepar’d a small Trough, about two Foot
long, and plac’d a Mint-Glass under each End of the Trough; over each
Glass I plac’d a Mint, with half its Roots in the Glass, the other
half in the Trough: The Mints stood just upon the Ends of the Trough.
Then I cover’d these Roots with pulveriz’d Earth, and kept the Glasses
supply’d with Water; and as oft as the white fibrous Roots shot thro’
the Earth, I threw on more Earth, till the Trough would hold no more;
and still the white Fibres came thro’, and appear’d above it; but all
seem’d (as I saw by the Help of a coarse Microscope) to turn, and when
they came above-ground, their Ends enter’d into it again. These two
_Mints_ grew thrice as large as any other _Mint_ I had, which were
many, that stood in Water, and much larger than those which stood in
Water with Earth in it: They being all of an equal Bigness when set in,
and set at the same time. Tho’ these two, standing in my Chamber, never
had any Water in their Earth, but what those Roots, which reach’d the
Water in the Glasses, sent up to the Roots, which grew in the Trough.
The vast Quantity of Water these Roots sent up, being sufficient to
keep all the Earth in the Troughs moist, tho’ of a thousand times
greater Quantity than the Roots which water’d it, makes it probable,
that the Water pass’d out of the Roots into the Earth, without mixing
at all with the Sap, or being alter’d to any Degree. The Earth kept
always moist, and in the hot Weather there would not remain a Drop of
Water in the Glasses, when they had not been fresh supply’d in two Days
and one Night; and yet these Roots in the Glasses were not dry’d, tho’
they stood sometimes a whole Day and Night thus in the empty Glasses.
These two Mints have thus liv’d all one Summer.
_Remarks on the_ Mints, _&c._
Tho’ the Vessels of Marine Plants be some ways fortify’d against the
Acrimony of Salt, as Sea-fish are, yet the Mints all shew, that Salt is
poison to other Plants.
The Reason why the Salts in Dung, Brine, or Urine, do not kill Plants
in the Field or Garden, is, that their Force is spent in acting upon,
and dividing the Parts of Earth; neither do these Salts, or at least
any considerable Quantity of them, reach the Roots.
I try’d Salt to many Potatoes in the Ground being undermin’d, and a few
of their Roots put into a Dish of Salt-water, they all died sooner or
later, according to their Bigness, and to the Proportions the Quantity
of Salt apply’d did bear to them.
By the Mints it appears, that Roots make no Distinctions in the Liquor
they imbibe, whether it be for their Nourishment or Destruction; and
that they do not insume what is disagreeable, or Poison to them, for
lack of other Sustenance; since they were very vigorous, and well fed
in the Glasses, at the time when the most inconsiderable Part of their
Number had the Salt, Garlick, and Ink offer’d to them.
The sixth _Mint_ shews, that when new Earth is apply’d to the old
Roots, a Plant sends out new Roots on Purpose to feed on it: And that
the more Earth is given it, the more Roots will be form’d, by the new
Vigour the Plant takes from the Addition of Earth. This corresponds
with the Action of Hoing; for every time the Earth is mov’d about
Roots, they have a Change of Earth, which is new to them.
The seventh _Mint_ proves, that there is such a Communication betwixt
all the Roots, that when any of them have Water, they do impart a Share
thereof to all the rest: And that the Root of the lower Joint of this
Mint had Passages (or Vessels) leading from them, through the Stalk, to
the Roots of the upper Joint; tho’ the clear Stalk (through which it
must have pass’d) that was betwixt these two Joints, was several Inches
in Length.
This accounts for the great Produce of long tap-rooted Plants, such as
_Lusern_ and _St. Foin_, in very dry Weather: for the Earth at a great
Depth is always moist. It accounts also for the good Crops we have in
dry Summers, upon Land that has a Clay Bottom; for there the Water is
retain’d a long time, and the lower Roots of Plants which reach it, do,
like those of this Mint, send up a Share to all the higher Roots.
If those Roots of a Plant, which lie at the Surface of the Ground, did
not receive Moisture from other Roots, which lie deeper, they could be
of no Use in dry Weather. But ’tis certain, that if this dry Surface be
mov’d or dung’d, the Plant will be found to grow the faster, tho’ no
Rain falls; which seems to prove, both that the deep Roots communicate
to the shallow a Share of their Water, and receive in Return from them
a Share of Food, in common with all the rest of the Plant, as in the
Mints they did.
The two last _Mints_ shew, that when the upper Roots have Moisture
(as they had in the Earth in the Trough, carried thither first by the
lower Roots) they impart some of it to the lower, else these could not
have continu’d plump and fresh, as they did for 24 Hours in the empty
Glass. And I have since observed them to do so, in the cooler Season
of the Year, for several Weeks together, without any other Water, than
what the upper Roots convey’d to them, from the moist Earth above in
the Trough[4]. I know not what Time these Roots might continue to be
supply’d thus in the hot Weather, because I did not try any longer, for
fear of killing them.
[4] ’Tis certain, that Roots and other Chyle Vessels of a Plant have
a free Communication throughout all their Cavities, and the Liquor in
them will run towards that Part where there is least Resistance; and
such is that which is the most empty, whether it be above or below;
for there are no _Valves_ that can hinder the Descent or Ascent of
Liquor in these Vessels, as appears by the growing of a Plant in an
inverted Posture.
But it must be noted, that the Depth of the Glass protected the Roots
therein from the Injury of the Motion of the free Air, which would have
dry’d them, if they had been out of the Glass.
In this Trough is shewn most of the Hoing Effects; _viz._ That Roots,
by being broken off near the Ends, increase their Number, and send out
several where one is broken off.
That the Roots increase their Fibres every time the Earth is stirr’d
about them.
That the stirring the Earth makes the Plants grow the faster.
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.