_On the Reproductive Organs of Acotyledonous plants_.
_17th_.--Fine weather, the sun daily increasing in power, is having a
remarkable effect on the peculiar spring vegetation, but this is not
sufficiently developed to bring in the corresponding birds and insects.
Gypaetos is common now about the dead camels.
On the low east ridge, along the path that leads over the river, ruins of
ancient times are discernible, this only adds another to the many proofs
of similarly situated ruins, that the people who built them have been
located about Cabul, Jallalabad, and Peshawur, certainly not about
Candahar.
In the soil between the rocks, and in their crevices saturated with
moisture, most of the plants are just sprouting. Trichonema, Crocus, and
one or two other monocotyledons, Labiatae? Sedum three or four species,
exclusive of Sedoides foliis deltoides sphathulatis, and a Stapelioid
Asclepias, are to be found. I also got a new fern, the fourth species
out of 1,300 sp. it is a Ceterach or Grammitis, a curious stalked snuff-
ball, and one or two other Fungi, with an inverted cap, were met with.
In the fields a young Ranunculus in profusion, Veronica agrestis,
Euphorbia, Festuca annua?
Kochia spinosa, and a curious Mathioloid are among the few wild plants to
be found about Pushut.
It would be a curious circumstance if all indusiate ferns were to be
found reducible to a _marginal production_ of the reproductive
apparatus. I will bear this in mind, as certain forms of Pteris or its
affinities lead me to suspect that in these tribes the indusium may be a
long way from the margin, and yet be, quoad origin, marginal; this
section illustrates my meaning.
[Fern sections: m444.jpg]
The transition to this might reasonably be suspected. The philosophy of
ferns is most ill understood, the higher points connected with them have
been quite neglected, and botanists in this as in other departments of
the science have been contented to confer names on certain external
forms, without sufficient regard to structure.
To-day I commenced examining Adiantum, with the view of determining if
possible the nature of its reproductive organs, and the mode in which
they are impregnated, if they are impregnated at all.
As I had long been aware that the fructification of each frond is a thing
to be determined at a very early period, and that if not determined then,
it is never likely to be determined afterwards, my attention was directed
more strongly, if possible, than it would have been otherwise, to
examining the subject at the earliest possible stage of its development.
The first piece examined gave me the idea that I had trouve le noeud de
l'affaire; the second made me doubt this; the subsequent ones went far to
disprove it.
I was immediately struck with the resemblance of those organs, called
ramenta, to what are fairly assumed to be the male bodies, in certain
other families of the same grand division; and I at once came to the
conclusion, that the barren fronds, were barren, because almost destitute
of these ramenta; and that as these ramenta were confined to the base of
the stalk, that is, to the part below its first ramification, an obvious
necessity existed for the peculiar nature of the vernation.
Further examination of the thing, especially of the base of the stipes
and the adjoining part of the rhizoma, threw me back almost into my
original difficulties. I find that the rhizoma is entirely covered with
ramenta, which are brown, much detached at the base, and obviously
represent a low form of leaf, i.e. in appearance, perhaps partly in
function, but not in structure. Among these, mature ramenta at the
punctas of prolongation, which appear to be very irregular, are
concealed, others much smaller, and much narrower, (which bear as obvious
a resemblance, or even more so to the male organs of certain other
orders,) than the ramenta on the stipes. These are never entirely brown,
the end cell alone is coloured, but though occasionally tinged with
brown, they are filled with some fluid (even this is not so at first,)
but do not appear to open. I believe that subsequently all become highly
tinged with brown, but what increase of growth they subsequently undergo,
I know not. The terminal cell is always solitary, very often attached to
the one next it, which is generally single, obliquely placed,
occasionally looking like the dimidiate calyptra capping a young seta.
The number of cells forming the base, or dilated part varies, but is
always small in proportion to the larger ramenta, or protecting scales:
these last have a single terminal cell, which in fact must be the same in
every really cellular growth _sooner or later_, the last degree of
formative power being the production of a single cell.
At a subsequent period, still an early one, the terminal cell is fuscous-
brown, and this colour then extends to the next in various degrees, but
if it reaches the basilar ones at all, it does so at late periods. The
base of the terminal cell, and parts of the parietes of the next and
next, present a coagulated appearance, precisely as in certain mosses.
No such thing as a petiolate leaf occurs in acrogens, all are attached by
a broad base? Of acrogenous leaves, those only are leaves whose
attachment is at right angles with the stem; the rest are divisions of a
frond. Thus far with the ramenta. The divisions of the frond, are, I
find, not gyrate, but rather cochleariform involate. The future
reproductiveness is settled at a very early period, and is
distinguishable under the microscope by a sort of _margination_ of the
frondlets. In the earliest stage I have looked at, the margin is
greenish, striated by narrow cells, and passes into the body of the leaf
gradually; the greater development is perhaps central; even now the bulk
of the cells of the leaflet have green granules, and are opaque from air.
The vessels are marked out, or at least their future course, and along
them the opacity from air does not exist, so that the veins appear
depressed.
The next stage presented a greater development of an isolation of the
margin, but no other change. The next presented an isolation of the
margin, which remains almost white, the other part being green, but more
so because of a thickening as it were along the base of the marginal
part, and an evident deposit of grumous matter, from which, under every
circumstance new tissue seems always to be developed. Pressure causes
its discharge, its contents were unappreciated by my poor instruments;
after this the leaflets revert to the appearance of the second stage.
Here I ceased for the day, having I think ascertained that ferns are
endorhizal, and that the primary divisions of the roots hence have
sheaths, which adhere to the apex of the root itself.--What a strange
union of roots, that of monocotyledons in the main divisions, and of pure
acrogens in the minor!!
I cannot help thinking that the secret is hidden in these ramenta, which,
as is known, are so universal as obviously to have higher functions than
those of mere covering scales. The appearance of those I have described
as existing about the points of growth, are exactly the same as the
processes mixed with the anthers of mosses, and of which the anthers are
nothing but more developed growths; this would point out, as indeed
appears to me otherwise evident, (especially from consideration of the
theca, and its want of style,) that ferns are lower organised as sexual
beings than mosses and Hepaticae. I know nothing of Lycopodineae, more
than they are the highest of all acrogens; and are not to be included in
the same category with ferns.
The objection to the ramenta being anthers, will be the closed nature
(_apparently_) of the terminal cell, and although the anthers of mosses
do burst, and most especially those of Hepaticae, yet the argument is not
conclusive--inasmuch as _boyaux_, to which they are analogous _do not_
_open_?
These ramenta explain fully the nature of those confervoid organs found
in some Neckerae, and perhaps in other mosses, and it becomes paramount
to prove whether these Neckerae have also the usual anthers, or if they
are confined to these, in which case a presumptive proof will thus be
afforded of their functions: if they have both forms, they will
nevertheless constitute an analogous passage between the two orders: if
they have only _these_, such Neckerae will form, as indeed they do, a
very distinct genus.
The nature of the barren fronds requires distinct analysis. Are they
barren from mere deficiency in supplies, such as may result from many
circumstances; or are the antheriform ramenta deficient? They are barren
from defective growth. I am aware how readily objection may be taken to
these views, some will say these young ramenta are nothing but young
scales as the older ones evidently are scales; but this amounts to
nothing, because we may expect simplicity in the sexual organs of this
division, and it will be only a proof of the uniformity of nature in
making so great a difference in a function depend on, or be associated
with so small a one in form. My view I think explains their uniformly
brown colour--analogous to Brown's sphacelation in mutatis mutandis.
Others will say how absurd the idea is, when you cannot show the place to
which the impregnating influence is to be applied. But the consideration
of mosses does away with this objection partly, and that of Anthoceros,
entirely; because in mosses, the _ovule_, or pre-existing cell, ready to
receive the male influence becomes an empty cell, terminating the seta;
and the sporula become developed at its opposite end, the first growth
appearing to be quite unconnected with that of the future reproductive
organs: and in Anthoceros there is no fixed punctum ready for the
application of the male organs, but these have to form a communication
with the lower, or inferior cellular tissue of the frond, before even the
growth of seta can commence.
Besides a case in point exists in Viscum, or Loranthus, in which no point
is ready prepared for the reception of the male influence; showing how
universal the law is, that in no one point or place is there an absolute
want of gradation.
As in mosses the influence of the male _disregarding the ovule_, is
thrown into the development of the seta, and then of the theca at the
apex of this; there can be no conclusive reason why in ferns the same
influence should be thrown into the development of the frond, and then
into that of the theca.
While Anthoceros proves that in these orders the male influence may exert
its effects upon any point.
As there is no styliform production in Anthoceros, so there is none in
ferns. If the ramenta be anthers, they will not be dubious ones, because
as they remain fixed, people cannot say, that possibly they are also
reproductive bodies, which by the bye is no objection at all, after
instances of anthers bearing _ovules_ instead of pollen!
Why the peculiar distribution of the male influence (on which we
determine our genera,) takes place, is another question, and one that
cannot be fairly asked?
Why it is confined to the under surface perhaps can, it being a law that
in all cases it is the under surface of the leaf, or its modification,
from which new growths originate, and as nature has closed indusia, how
could the under surface be interior if this rule were not regularly
adhered to?
That the indusium is a _special_ organ, i.e. not an eruption of the
cuticle, I am sure; hence it is essential to examine extensively both
indusiate and other forms, the precise extension of their veins, etc. at
an early period to ascertain if their most diversified situations cannot
be reduced to some one type.
_Query_. Is the gyrate vernation of any ferns comparable to the form of
certain shells, to which (at least Mollusca) ferns are supposed to be
analogous.
_Memo_. To ascertain the most peculiar, and most universal points of
Mollusca and Pseudo cotyledonea, it is in this way that we may hope to
extend our views. Some there are indeed who, while the whole course of
their studies has been to neglect structure, deny the applicability of
presumptive evidence in favour of doctrines, the subjects of which are
barely susceptible of direct proof. Thus Greville and Arnott, angrily
ask, what do persons mean by saying that mosses have pistilla, etc.? they
protest against such community of application in the use of terms. Many
more deny sexuality because it has not been proved. Considering the
invisible nature of the fluid of the anthers of mosses, etc. how do they
expect that we are to demonstrate its application to the pistil, and the
subsequent steps? As well might they doubt the necessity of the
application of the boyau to an ovule, (or the existence of the boyau
itself,) because the derivation of the embryo cannot be proved.
One word more; in all cases the appearance of the reproductive body after
impregnation, is of late date; that date becomes later as we descend the
scale. The embryonary sac of Phaenogams does not always exist at the
time of application of the boyau, and the appearance of the embryo is
always posterior to this.
Again, ferns are superior to mosses in this, that in many cases the male
influence is exerted directly on the parts that become the thecae, which
is not the case in mosses.
_18th_.--Continued examining ferns, and to-day completes my knowledge of
the ramenta of three different genera.
In the first which is Cryptogamma, the resemblance of the young ramenta
to the anthers of Jungermannia is evident enough, they are capital, and
the head is at one period filled with granular matter: so are the cells
throughout, to a greater or less extent. They are to be seen in all
stages of development on the pinnae of a very young frond, those near its
base having perhaps effected their purpose, while those at the apex of
the pinna, or the prolonging part of pinnula, may be formed of only one
cell. It is curious that the terminal cell does not become spherical for
some time: in its earlier stages it is cylindrical like the rest.
The appearances of the old ones are, if possible, more markedly in favour
of my hypothesis; there is the same aggregation of grumous _congealed_
matter about the ends of each cell, the same curious communication
between these masses which hide the septa from view, evincing a greater
or less tendency to assume the peculiar fuscesent or fusco-brown
appearance. I observed in two instances what appeared to me decided
irregular openings in the terminal cell, from one of which grumous
filaments projected; these appeared to communicate with the mass in the
terminal cell, which like that in all the others, is congealed; but it
assumes a different and very undefined form.
People may object and say, why were not more met with _opened_? This is
no objection, because it is obvious that a spherical body may be opened
in part of its surface, and yet unless this portion happens to be on the
_edge_ as it were of the sphere, it may escape detection with a
microscope of poor penetration.
In this the ramenta are confined, or nearly so, to the under surface of
the fronds. Most occupy that which is called the costa. In this the
first change as in Adiantum is in the definition of the margin. But this
point I have not paid much attention to, as with my present means here,
it would be absurd to attempt _proving_ how the fecundation takes place;
all that I can attempt is, to ascertain from structure and analogy, the
male nature of these curious bodies.
_See_ Plate _B_ for the various sketches. {450}
The next genus examined, is perhaps the instance in which these ramenta
have the strongest resemblance to ordinary simple hairs, both in their
young, when they represent succulent, tinged, grumous
molecular-containing hairs, and in the old, when they represent long,
flattened, coriaceous hairs, still there is abundant evidence to prove
that, however different these bodies are in appearance from those of
Cryptogamma, that they undergo the same changes, excepting perhaps as to
dehiscence. We have a tendency to fuscous colouring, a tendency to the
aggregation of congealed matter about the septae, precisely the places
where it is to be expected. The same appearance of a canal of
communication, the same irregular _constriction_ of certain cells; in
this too the first change in the pinnae, or its component lobes, is the
definition of the margin. In this genus the under surface of the frond
is covered with these _hairy-form_ bodies (which have been figured over
and over again in Hooker and Greville's ferns): on the upper face, a few
exist, but incomparably less developed.
From the examination of this genus alone, I do not think the idea I have
been so diffuse upon, would have struck me.
To-morrow I examine Ceterach, assured that the scales of its under face
are reducible to the same type. In a matter of such interest and
importance as this, many will, and with reason, dislike so important an
assumption on such inconclusive evidence. But with our present means, it
appears to me probable that no evidence to demonstration can be looked
for, and for this reason, that the contents of these peculiar cells are
so subtile as to escape definition even while in their cells, (or under
the most favourable circumstance for a concentration of attention.) How
much more so will this be the case, when we attempt to examine the steps
of the application of the fecundatory matter, applied over a surface
without any prominent points, and probably opaque.
When direct evidence is not to be had, we are justified in using
presumptive evidence. As in human law, so in the laws of nature,
presumptive evidence to a practised eye carries with it conviction. We
have no direct evidence how the embryo is formed, yet no one doubts but
that it is brought about by the agency of the boyau, which is a cell
containing grumous molecular matter. However different a boyau may seem
to many, yet when viewed in conjunction with Cycadeae, the graduation to
the present case becomes natural, and even the resemblance may be
perfect, because in Cycas the grains of pollen get into the nucleus
bodily, although they would still seem to throw out short tails.
Wonderful is the simplicity of nature! The male organ in its essence,
consists of a single cell containing molecular matter.
The female in its essence consists of a single cell, likewise containing
similar matter. The influence of the male is exerted, and so another
cell is formed in the female cell, and this either becomes the embryo, or
gives origin to another cell, and so on, until the terminal one becomes
the embryo.
I believe from examination of the most developed scaly ramenta, that
these have at an earlier period been fecundating organs, the same
peculiarities are to be detected towards their ends, where in fact they
retain their original structure, the dilated base being a subsequent
development.
In reference to this, the examination of young ferns on their arrival at
the age of puberty is indispensable. A curious question arises, what is
the frond of a fern? Is it a mass of foliaceous growth containing
certain lines of reproductive matter, or is it a distinct development
from the axis, in which the reproductive organs are situated? Is it, or
is it not, subservient to reproduction? Here again extensive examination
is necessary.
If it is altogether subordinate to reproduction, we may expect the
occurrence of far more simply constituted ferns than we are yet
acquainted with. In fact we may expect a form reduced to an axis, a few
ramenta, a frondose dilatation, and one punctum of reproductive organs.
With respect to duration, each frond is analogous to a single seta of a
moss, it has definite limits, and is unlike the fronds of certain
Hepaticae, which are capable of compound growth; or if this is the case
in ferns, as it is in viviparous ferns, the new formation becomes
separated from the frond, as a Phaenogamous gemma does. This is a
question of importance, as perhaps it may prove that all the foliaceous
forms, except Lycopodium, Equisetum, and Chara, are frondose; the dorsal
situation is in favour of this assumption, since in all the genuine
frondose forms, the reproductive organs of both kinds originate
immediately from the under surface, although they may protrude through
the upper.
I here ask, is there not _prima facie_ evidence that these organs have
peculiar functions; a peculiar form, attended with peculiar changes, must
have peculiar functions; and will any one show me in any single instance,
like circumstances to the like extent, in any of those organs called
hairs? By the bye, ferns themselves may prove that however like these
are to certain forms of hair, yet that their functions are different,
because the glandular hairs of ferns do not undergo the same alterations,
and are evidently nothing but hairs, probably secretory.
_19th_.--In Ceterach the same thing occurs precisely, with this
difference, that the _capita_ of the ramenta are highly developed; and
still more, that the terminations of each pinnula of the young frond, are
mere scales without a terminal _head_.
So that almost all the scales of the under surface of the lobes of the
mature frond, are mere scales. The peculiar ramenta are to be looked for
along the insertion of each pinna, and along the rachis, in which all
have the peculiar structure.
At the time that these scales are commencing their development, the
peculiar ones are at the age of mature perfection, so far as function
goes. No one can look at a young pinnula at this epoch and observe the
evident capitation of each ramentum, the inflexion of its apex, so that
the head is brought into contact with the frond, without suspecting that
they have the same relation of _cause_ to the appearance subsequently of
the thecae or capsules. It is curious that the colour of the scales is
the same as that of the ramenta, in which the colour is developed from
above _downwards_, a peculiarity as it appears to me.
The frond of Ceterach is very frondose-looking, it has stomata on its
under surface, and the cells of the cuticle very sinuate. There can be
no doubt of the propriety of including the nature of these ramenta and
scales in its generic character.
I can see nothing peculiar in the situation of the scales or ramenta to
suggest the reason of the situation of the capsules.
In several cases, each pinna appears to have scales only which become
barren lobes? the scales and ramenta have the same imbricate situation.
In this country it will be useless to expect more proofs. But the four
genera alluded to afford evidence enough, and sufficient to show that
these ramenta are formed with reference to some important function, that
their universality is incompatible with any functions of such minor
degree as are attributed to them by those who represent them to be scales
or hairs.
To those who require proof of the existence of the complex male organ of
Phaenogams, or of a male of that form with which only they are familiar,
I do not address myself; but to the philosophic botanist, who expects to
meet with in the lower orders of plants, a lower organization, one with a
tendency of reduction to the essential elements, and who bears in mind
the comparative anatomy and structure of similar bodies in adjoining, or
not very distant groups, I beg leave to suggest the intimate study of the
ramenta of Ferns.
Various as the situation of the fructification is, in three out of the
above four genera, yet the initial arrangements are precisely the same.
The various forms therefore may not depend proximately on fructification
itself, but on the peculiar growth given to the species, in the same way
in fact as we have the numerous modifications of the theca in mosses,
etc. and the infinite modifications of the carpels in Phaenogams.
(Attention is particularly pointed to those ferns which have general
capsules or involucres.
Above all to the Cyatheoid forms.
To Ophioglossum.
To naked Thecae.
To indusiate as Asplenia, etc.)
But however erroneous these views may be, they will still have been of
service if general attention is directed by them to plants, in
consequence of the suggestions they make. The time now thrown away on
isolated species, the station of which, still does not become fixed, when
devoted to the philosophical examination of ferns, will rescue botany
from one of its numerous reproaches. It is strange that such should
exist to the greatest degree in all those families stamped by nature as
most distinct. Those chaoses Polypodium, Aspidium, Davallia, would then
undergo distinct creation, and the primary divisions of the family would
become fixed; and we should then be spared the reproach of drawing
characters from organs, of the nature and functions of which we are quite
ignorant of, and of the importance of which in a science of demonstration
like that of botany, it is impossible to judge, without a true knowledge
of structure.
Vide Lindley's Introd. ed. 2, 407, for the protest of Greville and
Arnott.
What is the most comprehensive definition of a pistil. A case in which
the future organs of reproduction are developed; and here is a most
curious circumstance, namely, that though the calyptra, which is a
genuine pistillum containing an _ovulum_, becomes torn up from its base,
yet it remains in contact with that part of the seta in which the
sporules are developed until these make their appearance, or even later!!
so that one might as well deny a pistillum to a Reseda, or Leontice, as
deny it to these plants on the strength of its being torn from its
attachments. Sprengel's objections are worthy only of being noticed from
their having been quoted by Lindley. The vagueness of his statement
destroys all weight.
His objections in all cases amount to the fact, that the _stellulae_ or
_buds_ containing the anthers are capable of growth. So is the
prolongation of an axis of Ananassa.
A Gemma has a general character in its formation as well as an anther, or
as pollen; one is a congeries of cellular tissue, with or without
vessels, the other a sac consisting of a single cell containing active
molecular matter. As an anther producing a single grain of pollen is not
inconsistent with our notions of structure, so neither is an anther
consisting of a single grain of pollen.
Will any one show me an instance of a proved gemma taking upon itself the
form of one of these anthers? Will any show an instance of a sac
containing fluid matter capable of growth _after dehiscence_. The real
gemmae of the Hepaticae puts the question of gemmae out of doubt. Is
there any plant existing with two sorts of gemmae, so differently
constituted? Many phaenogams have gemma in addition to sexes, so have
Hepaticae. Which is the most probable? That they should have no sexes,
reproductive organs, and two sorts of gemmae, or sexes, reproductive
organs, or gemmae of one evident kind?
I cannot adopt the belief of any one having seen the germination of the
powder in the axillary bodies, that is, if applicable to the organs I
take for anthers.
(_Memorandum_.--To draw up a parallel between the two sets of organs, and
the steps followed in the development of each.)