The Metamorphosis of Plants (6 page)

The opinion set forth in the preceding paragraph appears still more probable when we think of the near relationship of the petals with the stamens.
If the relationship between all the other organs were so obvious, so generally noticed and set beyond doubt, the present essay might seem superfluous.

Nature shows us this transition between petals and stamens taking place normally in several instances, in
Canna
, for example and in other plants of this family.
Here a true but slightly changed petal contracts at the upper edge and an anther appears, in relation to which the rest of the petal takes the place of the filament.

In those plants which often produce double blossoms we can observe this transition in all its stages.
In many kinds of roses, among the perfectly formed and coloured petals, other petals may appear which are contracted partly in the middle and partly at the sides.
This contraction is caused by a little weal or protuberance which more or less resembles a perfect anther, while in just the same proportion the petal begins to take on the simpler form of a stamen.
In some double poppies, fully developed anthers rest on petals of the thickly filled corolla which are very little changed; in others the petals are more or less drawn together by anther-like weals.

If all the stamens change into petals the flower will be
seedless, but if in a flower which appears double, stamens are still developed, then fertilisation will take place.

Thus a stamen is produced when the organs, which until now we have seen expanding into petals, reappear in an extremely contracted and at the same time refined state.
This once more confirms the truth of the observation put forward above, and we are made more and more aware of the alternating process of contraction and expansion whereby Nature at last reaches her goal.

Quick as the transition is in some plants from the corolla to the stamens, we perceive that Nature is not able to complete it in one step, but produces intermediate organs which resemble in form and effect sometimes one part of the plant and sometimes another.
Although they vary greatly in form these organs may mostly be united under one heading: they are slow transitions from the petals to the stamens.

In effect, most of those variedly formed organs, which Linnaeus called nectaries, may be thus defined, and here again we have occasion to admire the keen power of penetration of this extraordinary man, who, without coming to a perfectly clear understanding of the function of these parts, trusted to his intuitive feeling and ventured to give a single name to such seemingly different organs.

Various petals show us their relationship to stamens; without noticeably changing their form they have little cavities
or glands which secrete a kind of honey-juice.
That this juice is a yet unelaborated and not yet fully differentiated fertilizing fluid we can to some extent surmise from the above considerations, and we shall be supported in this by further reasons which will be brought forward later on.

The so-called nectaries may also appear as independent organs and then they are formed sometimes like petals, sometimes like stamens.
Thus, for example, the thirteen filaments, each with its little red ball, on the nectaries of
Parnassia
, very much resemble stamens.
Others look like stamens without anthers, as for example in
Valisneria
or
Feuillea
, while in
Pentapetes
we find them in a circle alternating regularly with the stamens and in leaf-like form.
In systematic descriptions too these organs are called
Filamenta castrata petaliformia.
Similar ambiguous forms are to be seen in
Kigellaria
and the Passion-flower.

In this sense the “secondary corollas” seem likewise to deserve the name of nectaries.
For if the forming of the petals comes about through a kind of expansion, the secondary corollas on the other hand are formed by contraction, that is to say, in just the same way as the stamens.
And so we see within perfectly expanded corollas smaller, contracted, secondary ones, as for example in the
Narcissus, in Nerium
and in
Agrostemma.

Furthermore, in various species we see alterations which are still more striking and remarkable.
In some flowers we notice a little hollow filled with honey-like juice at the inner base of the petals.
This little cavity becomes deeper in some species and types than in others and produces on the back of the petal a spur or horn-like protuberance, the shape of the rest of the petal being at the same time more or less modified.
This can be distinctly seen in many types and variations of
Aquilegia.

We find the nectary most transformed in
Aconitum
and in
Nigella
, but even here only a little attention will enable us to see its resemblance to a leaf.
In
Nigella
especially it tends to grow into a leaf or petal and through the transformation of the nectaries the flower becomes double.
In
Aconitum
it is easy to see the resemblance of the nectaries to the domed-shaped petals under which they are hidden.

Having already said that the nectaries are a transitional stage between petals and stamens we may at this point say a few words about irregular flowers.
The five outer petals of
Melianthus
, for example, could be described as true petals, but the five inner ones as a secondary' corolla consisting of six nectaries, of which the uppermost nearly resembles the leaf-form while the lower—which is indeed called the nectary—differs most from it.
In this same sense the
carina
or keel of the Papi-lionaceae might be called a nectary in so far as it, of all the petals of this flower, is nearest in form to the stamens and differs greatly from the leaf-like form of the so-called
vexilli.
In this way too we may easily explain the brush-like appendages which are attached to the end of the
carina
of some species of
Polygala
: so shall we form a distinct idea of the real meaning of these organs.

It is hardly necessary to avow that these remarks are not intended to bring into confusion all that has hitherto been separated and classified through the endeavours of observers and systematists.
We only wish to explain more clearly the variable formations and developments of the plant-kingdom.

Microscopic observations have placed it beyond doubt that
the generative organs of the plants as well as other organs are produced by spiral vessels.
We take this as a basis for the argument that the different parts of the plant, which have so far manifested themselves to us in such varied forms, are none the less intrinsically the same.

Now as the spiral vessels are situated in the middle of the bundles (vascular bundles) and are enclosed by them, we can to some extent come to a better understanding of the above-mentioned strong contracting force if we imagine the spiral vessels, which really look like elastic springs, exerting their utmost power so that they overcome the expansive tendency of the sap-vessels.

The shortened vascular bundles can then no longer expand; they are not able to unite so as to form a network by anastomosis, and the cellular tissue, which otherwise fills up the spaces of the network, can no longer develop.
Here, all the causes for the expansion of stem-leaves, calix and petals are at an end, and there appears a frail, extremely simple thread or filament.

Hardly are the fine little membranes of the anther formed, than the extremely delicate vessels terminate in them.
Now if we admit that here the very same vessels, which otherwise become lengthened and expanded and united with one another, are at this stage in an extremely contracted condition; if, moreover, we see coming from them the highly developed pollen which through its active energy compensates for what the vessels that have brought it forth have lost in their power of expansion; if when set free it seeks the feminine parts which through the same working of Nature have grown up near the stamens; if it attaches itself fast to the pistils and imparts its influence to them—then at long last we are not disinclined to call the union of the male and female organs a
spiritual anastomosis
, and we believe we have brought the concepts of
growth and reproduction, at least for a moment, a little nearer to one another.

The fine substance, which is developed in the anthers, looks like a kind of dust; but these little balls of pollen are in fact vessels or cells for the preservation of an extremely refined juice.
We agree with the opinion of those who maintain that this juice is absorbed by the pistils to which the pollen-balls attach themselves, fructification being in this way effected.
This becomes even more credible when we think that some plants do not give off pollen grains, but only a kind of fluid.

We are here reminded of the honey-like juice of the nectaries and its probable relation to the more elaborated fluid of the pollen grains.
Perhaps the nectaries are organs for preparation and maybe their honey-like moisture is drawn in by the anthers and then more fully perfected and elaborated—quite a plausible opinion, for this sap is no longer to be seen after fructification.

We will not omit to mention here in passing that the filaments as well as the anthers, grow together in many different ways, showing what we have so often described, namely the anastomosis and union of organs which in their beginnings were quite apart and distinct.

If until now I have tried to show as far as has been possible that the different parts of the plant as they develop one
after the other, even though they may greatly differ in outward form, are intrinsically the same, it will easily be surmised that my aim will now be to explain in this way too the structure of the feminine parts.

At first we will consider the style and stigma of the pistil apart from the actual ovary, as indeed, we often find it in Nature.
This we may the more easily do, as it reveals a characteristic and distinct form.

We observe then, that the pistil is at the same stage of growth as the stamens.
We noticed that the stamens were produced through a contraction; this is also often the case with the styles, and we see that, though not always just the same length as the stamens, yet they are only a little longer or shorter.
In many cases the style looks almost like a filament without an anther, and the two are more nearly allied in exterior form than any of the remaining parts.
As they are both produced by spiral cells, we see all the more clearly that the feminine part is no more a distinct organ than the masculine part, and when through this observation the close relationship of these feminine parts with the masculine becomes evident to us, we find it all the more appropriate and illuminating to think of their union as a kind of anastomosis.

We very often find the pistil formed by the growing together of several single ones, the component parts being hardly distinguishable at the tip, where they are not even separated.
This growing together, the effect of which we have often remarked upon, takes place in this instance most easily of all.
Indeed, it must happen, for the delicate organs, before they are perfectly developed, are pressed together in the blossom and thus enabled intimately to unite with one another.

In various normal cases Nature shows us more or less
clearly the near relationship of the pistil with the preceding parts of the blossom.
For example, the pistil of the iris appears with its stigma in the perfected form of a petal.
The umbrella-shaped stigma of
Sarracenia
shows that it is composed of several leaves set together.
True, this is not so marked and yet even the green colour is retained.
With the help of the microscope we find more stigmas formed like perfect one- or many-leaved calyces in the crocus, for example, or
Zannichellia.

By a retrogressive development Nature often shows us instances where the style and stigma have changed back again into petals; the
Ranunculus asiaticus
, for example, becomes double in this way, the stigmas and styles having transformed themselves into true petals, while the anthers, immediately underneath, may often be found unchanged.
One or two other remarkable instances will come to our attention later on.

We will here repeat the observations already made: that pistil and the stamens are at the same stage of growth and illustrate once again the fundamental principle of alternate expansion and contraction.
From the seed to the most perfect development of the stem-leaf we first observe expansion; then we saw the calyx being formed through a contraction; the petals by expansion; the reproductive organs again by contraction; and now we shall soon become aware of the greatest expansion and contraction of all, namely the expansion in the fruit and the contraction again in the seed.
In these six steps Nature continually completes her endless work of the propagation of plants by the two sexes.