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Micrographia by Robert Hooke

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Observ. XVIII. _Of the _Schematisme_ or _Texture_ of _Cork_, and of the
Cells and Pores of some other such frothy Bodies._

I took a good clear piece of Cork, and with a Pen-knife sharpen'd as keen
as a Razor, I cut a piece of it off, and thereby left the surface of it
exceeding smooth, then examining it very diligently with a _Microscope_, me
thought I could perceive it to appear a little porous; but I could not so
plainly distinguish them, as to be sure that they were pores, much less
what Figure they were of: But judging from the lightness and yielding
quality of the Cork, that certainly the texture could not be so curious,
but that possibly, if I could use some further diligence, I might find it
to be discernable with a _Microscope_, I with the same sharp Penknife, cut
off from the former smooth surface an exceeding thin piece of it, and
placing it on a black object Plate, because it was it self a white body,
and casting the light on it with a deep _plano-convex Glass_, I could
exceeding plainly perceive it to be all perforated and porous, much like a
Honey-comb, but that the pores of it were not regular; yet it was not
unlike a Honey-comb in these particulars.

First, in that it had a very little solid substance, in comparison of the
empty cavity that was contain'd between, as does more manifestly appear by
the Figure A and B of the XI. _Scheme_, for the _Interstitia_, or walls (as
I may so call them) or partitions of those pores were neer as thin in
proportion to their pores, as those thin films of Wax in a Honey-comb
(which enclose and constitute the _sexangular celts_) are to theirs.

Next, in that these pores, or cells, were not very deep, but consisted of a
great many little Boxes, separated out of one continued long pore, by
certain _Diaphragms_, as is visible by the Figure B, which represents a
sight of those pores split the long-ways.

I no sooner discern'd these (which were indeed the first _microscopical_
pores I ever saw, and perhaps, that were ever seen, for I had not met with
any Writer or Person, that had made any mention of them before this) but me
thought I had with the discovery of them, presently hinted to me the true
and intelligible reason of all the _Phaenomena_ of Cork; As,

First, if I enquir'd why it was so exceeding light a body? my _Microscope_
could presently inform me that here was the same reason evident that there
is found for the lightness of froth, an empty Honey-comb, Wool, a Spunge, a
Pumice-stone, or the like; namely, a very small quantity of a solid body,
extended into exceeding large dimensions.

Next, it seem'd nothing more difficult to give an intelligible reason, why
Cork is a body so very unapt to suck and drink in Water, and consequently
preserves it self, floating on the top of Water, though left on it never so
long: and why it is able to stop and hold air in a Bottle, though it be
there very much condens'd and consequently presses very strongly to get a
passage out, without suffering the least bubble to pass through its
substance. For, as to the first, since our _Microscope_ informs us that the
substance of Cork is altogether fill'd with Air, and that that Air is
perfectly enclosed in little Boxes or Cells distinct from one another. It
seems very plain, why neither the Water, nor any other Air can easily
insinuate it self into them, since there is already within them an _intus
existens_, and consequently, why the pieces of Cork become so good floats
for Nets, and stopples for Viols, or other close Vessels.

And thirdly, if we enquire why Cork has such a springiness and swelling
nature when compress'd? and how it comes to suffer so great a compression,
or seeming penetration of dimensions, so as to be made a substance as
heavie again and more, bulk for bulk, as it was before compression, and yet
suffer'd to return, is found to extend it self again into the same space?
Our _Microscope_ will easily inform us, that the whole mass consists of an
infinite company of small Boxes or Bladders of Air, which is a substance of
a springy nature, and that will suffer a considerable condensation (as I
have several times found by divers trials, by which I have most evidently
condens'd it into less then a twentieth part of its usual dimensions neer
the Earth, and that with no other strength then that of my hands without
any kind of forcing Engine, such as Racks, Leavers, Wheels, Pullies, or the
like, but this onely by and by) and besides, it seems very probable that
those very films or sides of the pores, have in them a springing quality,
as almost all other kind of Vegetable substances have, so as to help to
restore themselves to their former position.

And could we so easily and certainly discover the _Schematisme_ and
_Texture_ even of these films, and of several other bodies, as we can these
of Cork; there seems no probable reason to the contrary, but that we might
as readily render the true reason of all their _Phaenomena_; as namely,
what were the cause of the springingess, and toughness of some, both as to
their flexibility and restitution. What, of the friability or brittleness
of some others, and the like; but till such time as our _Microscope_, or
some other means, enable us to discover the true _Schematism_ and _Texture_
of all kinds of bodies, we must grope, as it were, in the dark, and onely
ghess at the true reasons of things by similitudes and comparisons.

But, to return to our Observation. I told several lines of these pores, and
found that there were usually about threescore of these small Cells placed
end-ways in the eighteenth part of an Inch in length, whence I concluded
there must be neer eleven hundred of them, or somewhat more then a thousand
in the length of an Inch, and therefore in a square Inch above a Million,
or 1166400. and in a Cubick Inch, above twelve hundred Millions, or
1259712000. a thing almost incredible, did not our _Microscope_ assure us
of it by ocular demonstration; nay, did it not discover to us the pores of
a body, which were they _diaphragm'd_, like those of Cork, would afford us
in one Cubick Inch, more then ten times as many little Cells, as is evident
in several charr'd Vegetables; so prodigiously curious are the works of
Nature, that even these conspicuous pores of bodies, which seem to be the
channels or pipes through which the _Succus nutritius_, or natural juices
of Vegetables are convey'd, and seem to correspond to the veins, arteries
and other Vessels in sensible creatures, that these pores I say, which seem
to be the Vessels of nutrition to the vastest body in the World, are yet so
exceeding small, that the _Atoms_ which _Epicurus_ fancy'd would go neer to
prove too bigg to enter them, much more to constitute a fluid body in them.
And how infinitely smaller then must be the Vessels of a Mite, or the pores
of one of those little Vegetables I have discovered to grow on the
back-side of a Rose-leaf, and shall anon more fully describe, whose bulk is
many millions of times less then the bulk of the small shrub it grows on;
and even that shrub, many millions of times less in bulk then several trees
(that have heretofore grown in _England_, and are this day flourishing in
other hotter Climates, as we are very credibly inform'd) if at least the
pores of this small Vegetable should keep any such proportion to the body
of it, as we have found these pores of other Vegetables to do to their
bulk. But of these pores I have said more elsewhere.

To proceed then, Cork seems to be by the transverse constitution of the
pores, a kind of _Fungus_ or Mushrome, for the pores lie like so many Rays
tending from the center, or pith of the tree, outwards; so that if you cut
off a piece from a board of Cork transversly, to the flat of it, you will,
as it were, split the pores, and they will appear just as they are
express'd in the Figure B of the XI. _Scheme_. But if you shave off a very
thin piece from this board, parallel to the plain of it, you will cut all
the pores transversly, and they will appear almost as they are express'd in
the Figure A, save onely the solid _Interstitia_ will not appear so thick
as they are there represented.

So that Cork seems to suck its nourishment from the subjacent bark of the
Tree immediately, and to be a kind of excrescence, or a substance distinct
from the substances of the entire Tree, something _analogus_ to the
Mushrome, or Moss on other Trees, or to the hairs on Animals. And having
enquir'd into the History of Cork, I find it reckoned as an excrescency of
the bark of a certain Tree, which is distinct from the two barks that lie
within it, which are common also to other trees; That 'tis some time before
the Cork that covers the young and tender sprouts comes to be discernable;
That it cracks, flaws, and cleaves into many great chaps, the bark
underneath remaining entire; That it may be separated and remov'd from the
Tree, and yet the two under-barks (such as are also common to that with
other Trees) not at all injur'd, but rather helped and freed from an
external injury. Thus _Jonstonus_ in _Dendrologia_, speaking _de Subere_,
says, _Arbor est procera, Lignum est robustum, dempto cortice in aquis non
fluitat, Cortice in orbem detracto juvatur, crascescens enim praestringit &
strangulat, intra triennium iterum repletur: Caudex ubi adolescit crassus,
cortex superior densus carnosus, duos digitos crassus, scaber, rimosus, &
qui nisi detrahatur dehiscit, alioque subnascente expellitur, interior qui
subest novellus ita rubet ut arbor minio picta videatur_. Which Histories,
if well consider'd, and the tree, substance, and manner of growing, if well
examin'd, would, I am very apt to believe, much confirm this my conjecture
about the origination of Cork.

Nor is this kind of Texture peculiar to Cork onely; for upon examination
with my _Microscope_, I have found that the pith of an Elder, or almost any
other Tree, the inner pulp or pith of the Cany hollow stalks of several
other Vegetables: as of Fennel, Carrets, Daucus, Bur-docks, Teasels, Fearn,
some kinds of Reeds, &c. have much such a kind of _Schematisme_, as I have
lately shewn that of Cork, save onely that here the pores are rang'd the
long-ways, or the same ways with the length of the Cane, whereas in Cork
they are transverse.

The pith also that fills that part of the stalk of a Feather that is above
the Quil, has much such a kind of texture, save onely that which way soever
I set this light substance, the pores seem'd to be cut transversly; so that
I ghess this pith which fills the Feather, not to consist of abundance of
long pores separated with Diaphragms, as Cork does, but to be a kind of
solid or hardned froth, or a _congeries_ of very small bubbles consolidated
in that form, into a pretty stiff as well as tough concrete, and that each
Cavern, Bubble, or Cell, is distinctly separate from any of the rest,
without any kind of hole in the encompassing films, so that I could no more
blow through a piece of this kinde of substance, then I could through a
piece of Cork, or the sound pith of an Elder.

But though I could not with my _Microscope_, nor with my breath, nor any
other way I have yet try'd, discover a passage out of one of those cavities
into another, yet I cannot thence conclude, that therefore there are none
such, by which the _Succus nutritius_, or appropriate juices of Vegetables,
may pass through them; for, in several of those Vegetables, whil'st green,
I have with my _Microscope_, plainly enough discover'd these Cells or Poles
fill'd with juices, and by degrees sweating them out; as I have also
observed in green Wood all those long _Microscopical_ pores which appear in
Charcoal perfectly empty of any thing but Air.

Now, though I have with great diligence endeavoured to find whether there
be any such thing in those _Microscopical_ pores of Wood or Piths, as the
_Valves_ in the heart, veins, and other passages of Animals, that open and
give passage to the contain'd fluid juices one way, and shut themselves,
and impede the passage of such liquors back again, yet have I not hitherto
been able to say any thing positive in it; though, me thinks, it seems very
probable, that Nature has in these passages, as well as in those of Animal
bodies, very many appropriated Instruments and contrivances, whereby to
bring her designs and end to pass, which 'tis not improbable, but that some
diligent Observer, if help'd with better _Microscopes_, may in time detect.

And that this may be so, seems with great probability to be argued from the
strange _Phaenomena_ of sensitive Plants, wherein Nature seems to perform
several Animal actions with the same _Schematism_ or _Orginization_ that is
common to all Vegetables, as may appear by some no less instructive then
curious Observations that were made by divers Eminent Members of the _Royal
Society_ on some of these kind of Plants, whereof an account was delivered
in to them by the most Ingenious and Excellent _Physician_, Doctor _Clark_,
which, having that liberty granted me by that most Illustrious Society, I
have hereunto adjoyn'd.

_Observations on the _Humble_ and _Sensible Plants_ in _M Chiffin's_ Garden
in Saint _James_'s Park, made _August_ the _9th, 1661_._ _Present, the_
Lord _Brouncker_, Sr. _Robert Moray_, Dr. _Wilkins_, Mr. _Evelin_, Dr.
_Henshaw_, _and_ Dr. _Clark_.

There are four Plants, two of which are little shrub Plants, with a
little short stock, about an Inch above the ground, from whence are
spread several sticky branches, round, streight, and smooth in the
distances between the Sprouts, but just under the Sprouts there are two
sharp thorny prickles, broad in the letting on, as in the Bramble, one
just under the Sprout, the other on the opposite side of the branch.

[14]The distances betwixt the Sprouts are usually something more then
an Inch, and many upon a Branch, according to its length, and they grew
so, that if the lower Sprout be on the left side of the Branch, the
next above is on the right, and so to the end, not sprouting by pairs.

At the end of each Sprout are generally four sprigs, two at the
Extremity, and one on each side, just under it. At the first sprouting
of these from the Branch to the Sprig where the leaves grow, they are
full of little short white hairs, which wear off as the leaves grow,
and then they are smooth as the Branch.

Upon each of these sprigs, are, for the most part, eleven pair of
leaves, neatly set into the uppermost part of the little sprig, exactly
one against another, as it were in little _articulations_, such as
Anatomists call _Enarthrosis_, where the round head of a Bone is
received into another fitted for its motion; and standing very fitly to
shut themselves and touch, the pairs just above them closing somewhat
upon them, as in the shut sprig; so is the little round _Pedunculus_ of
this leaf fitted into a little cavity of the sprig, visible to the eye
in a sprig new pluck'd, or in a sprig withered on the Branch, from
which the leaves easily fall by touching.

The leaf being almost an oblong square, and set into the _Pedunculus_,
at one of the lower corners, receiveth from that not onely a _Spine_,
as I may call it, which, passing through the leaf, divides it so
length-ways that the outer-side is broader then the inner next the
sprig, but little _fibres_ passing obliquely towards the opposite
broader side, seem to make it here a little muscular, and fitted to
move the whole leaf, which, together with the whole sprig, are set full
with little short whitish hairs.

One of these Plants, whose branch seem'd to be older and more grown
then the other, onely the tender Sprouts of it, after the leaves are
shut, fall and hang down; of the other, the whole branches fall to the
ground, if the Sun shine very warm, upon the first taking off the
Glass, which I therefore call the _humble Plant_.

The other two, which do never fall, nor do any of their branches flagg
and hang down, shut not their leaves, but upon somewhat a hard stroke;
the stalks seem to grow up from a root, and appear more _herbaceous_,
they are round and smooth, without any prickle, the Sprouts from them
have several pairs of sprigs, with much less leaves then the other on
them, and have on each sprig generally seventeen pair.

Upon touching any of the sprigs with leaves on, all the leaves on that
sprig contracting themselves by pairs, joyned their upper superficies
close together.

Upon the dropping a drop of _Aqua fortis_ on the sprig betwixt the
leaves, ff all the leaves above shut presently, those below by pairs
successively after, and by the lower leaves of the other branches, ll,
kk, &c. and so every pair successively, with some little distance of
time betwixt, to the top of each sprig, and so they continu'd shut all
the time we were there. But I returning the next day, and several days
since, found all the leaves dilated again on two of the sprigs; but
from ff, where the _Aqua fortis_ had dropped upwards, dead and
withered; but those below on the same sprig, green, and closing upon
the touch, and are so to this day, _August_ 14.

With a pair of Scissers, as suddenly as it could be done, one of the
leaves bb was clipped off in the middle, upon which that pair, and the
pair above, closed presently, after a little interval, dd, then ee, and
so the rest of the pairs, to the bottom of the sprig, and then the
motion began in the lower pairs, ll, on the other sprigs, and so shut
them by pairs upwards, though not with such distinct distances.

Under a pretty large branch with its sprigs on, there lying a large
Shell betwixt two and three Inches below it, there was rubbed on a
strong sented oyl, after a little time all the leaves on that sprig
were shut, and so they continued all the time of our stay there, but at
my returne the next day, I found the position of the Shell alter'd, and
the leaves expanded as before, and closing upon the touch.

Upon the application of the Sun-beams by a Burning-glass, the more
_humble Plant_ fell, the other shut their leaves.

We could not so apply the smoak of _Sulpher_, as to have any visible
effect from that, at two or three times trial; but on another trial,
the smoak touching the leaves, it succeeded.

The _humble Plant_ fell upon taking off the Glass wherewith it was
covered.

Cutting off one of the little Sprouts, two or three drops of liquor
were thrust out of the part from whence that was cut, very cleer, and
pellucid, of a bright greenish colour, tasting at first a little
bitterish, but after leaving a licorish-like taste in my mouth.

Since, going two or three times when it was cold, I took the Glasses
from the more _humble Plant_, and it did not fall as formerly, but shut
its leaves onely. But coming afterwards, when the Sun shone very warm,
as soon as it was taken off, it fell as before.

Since I pluck'd off another sprig, whose leaves were all shut, and had
been so some time, thinking to observe the liquor should come from that
I had broken off, but finding none, though with pressing, to come, I,
as dexterously as I could, pull'd off one whose leaves were expanded,
and then had upon the shutting of the leaves, a little of the mention'd
liquor, from the end of the sprig I had broken from the Plant. And this
twice successively, as often almost as I durst rob the Plant.

But my curiosity carrying me yet further, I cut off one of the harder
branches of the stronger Plant, and there came of the liquor, both from
that I had cut, and that I had cut it from, without pressure.

Which made me think, that the motion of this Plant upon touching, might
be from this, that there being a constant _intercourse_ betwixt every
part of this Plant and its root, either by a _circulation_ of this
liquor, or a constant pressing of the subtiler parts of it to every
extremity of the Plant. Upon every pressure, from whatsoever it
proceeds, greater then that which keeps it up, the subtile parts of
this liquor are thrust downwards, towards its _articulations_ of the
leaves, where, not having room presently to get into the sprig, the
little round _pedunculus_, from whence the _Spine_ and those oblique
_Fibres_ I mentioned rise, being dilated, the _Spine_ and _Fibres_
(being continued from it) must be contracted and shortned, and so draw
the leaf upwards to joyn with its fellow in the same condition with it
self, where, being closed, they are held together by the implications
of the little whitish hair, as well as by the still retreating liquor,
which distending the _Fibres_ that are continued lower to the branch
and root, shorten them above; and when the liquor is so much forced
from the Sprout, whose _Fibres_ are yet tender, and not able to support
themselves, but by that tensness which the liquor filling their
_interstices_ gives them, the Sprout hangs and flags.

But, perhaps, he that had the ability and leisure to give you the exact
_Anatomy_ of this pretty Plant, to shew you its _Fibres_, and visible
_Canales_, through which this fine liquor circulateth, or is moved, and
had the faculty of better and more copiously expressing his
Observations and conceptions, such a one would easily from the motion
of this liquor, solve all the _Phaenomena_, and would not fear to
affirm, that it is no obscure sensation this Plant hath. But I have
said too much, I humbly submit, and am ready to stand corrected.

I have not yet made so full and satisfactory Observations as I desire on
this Plant, which seems to be a Subject that will afford abundance of
information. But as farr as I have had opportunity to examine it, I have
discovered with my _Microscope_ very curious structures and contrivances;
but designing much more accurate examinations and trials, both with my
_Microscope_, and otherwise, as soon as the season will permit, I shall not
till then add any thing of what I have already taken notice of; but as farr
as I have yet observ'd, I judge the motion of it to proceed from causes
very differing from those by which Gut-strings, or Lute-strings, the beard
of a wilde _Oat_, or the beard of the Seeds of _Geranium_, _Mosscatum_, or
_Musk-grass_ and other kinds of _Cranes-bill_, move themselves. Of which I
shall add more in the subsequent Observations on those bodies.

* * * * *


Observ. XIX. _Of a _Plant_ growing in the blighted or yellow specks of
_Damask-rose-leaves_, _Bramble-leaves_, and some other kind of leaves._

I have for several years together, in the Moneths of _June_, _July_,
_August_, and _September_ (when any of the green leaves of _Roses_ begin to
dry and grow yellow) observ'd many of them, especially the leaves of the
old shrubs of _Damask Roses_, all bespecked with yellow stains; and the
undersides just against them, to have little yellow hillocks of a gummous
substance, and several of them to have small black spots in the midst of
those yellow ones, which, to the naked eye, appear'd no bigger then the
point of a Pin, or the smallest black spot or tittle of Ink one is able to
make with a very sharp pointed Pen.

Examining these with a _Microscope,_ I was able plainly to distinguish, up
and down the surface, several small yellow knobs, of a kind of yellowish
red gummy substance, out of which I perceiv'd there sprung multitudes of
little cases or black bodies like Seed-cods, and those of them that were
quite without the hillock of Gumm, disclos'd themselves to grow out of it
with a small Straw-colour'd and transparent stem, the which seed and stem
appear'd very like those of common Moss (which I elsewhere describe) but
that they were abundantly less, many hundreds of them being not able to
equalize one single seed Cod of Moss.

I have often doubted whether they were the seed Cods of some little Plant,
or some kind of small Buds, or the Eggs of some very small Insect, they
appear'd of a dark brownish red, some almost quite black, and of a Figure
much resembling the seed-cod of Moss, but their stalks on which they grew
were of a very fine transparent substance, almost like the stalk of mould,
but that they seem'd somewhat more yellow.

That which makes me to suppose them to be Vegetables, is for that I
perceiv'd many of those hillocks bare or destitute, as if those bodies lay
yet conceal'd, as G. In others of them, they were just springing out of
their gummy hillocks, which all seem'd to shoot directly outwards, as at A.
In others, as at B, I found them just gotten out, with very little or no
stalk, and the Cods of an indifferent cize; but in others, as C, I found
them begin to have little short stalks, or stems; in others, as D, those
stems were grown bigger, and larger; and in others, as at E, F, H, I, K, L,
&c. those stems and Cods were grown a great deal bigger, and the stalks
were more bulky about the root, and very much taper'd towards the top, as
at F and L is most visible.

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