=Relative position of organs.=--When organs are considered, not separately, but in their relations to each other, the appearances presented are referable to similar causes. Thus, the separation of parts usually united has been shown to depend on an excess of development, the persistent union of parts, usually separate in the adult state, has been traced to an arrest of the process of development, by no means necessarily coexistent with diminished growth. The diminished or increased number of parts is, in like manner, attributable to a.n.a.logous causes, as also are the variations in arrangement and form, spoken of under the heads of Displacement, Peloria, Subst.i.tution, &c.

In the instance of displacements, it has been shown how slight a change is required to transform the so-called inferior ovary into a superior one. A defective development of the top of the flower-stalk in some cases, in others a lack of union between the tube of the receptacle or of the calyx (comprising in those terms not only the apex of the receptacle, but the base of the sepals) and the carpels, suffice to bring about this change in a character which for systematic purposes is of great value.

=Law of alternation.=--The circ.u.mstances that interfere with the law of alternation may be briefly alluded to. The deviations from the customary arrangement have been very generally attributed to suppression, or to chorisis. It is unquestionable that either of these affords an efficient explanation of the arrangement in question, as also does that modification of chorisis, as it may be considered, which has been treated of under the head of Enation. Spiral torsion of the axis would likewise bring about a.n.a.logous results. Still, it is quite conceivable that opposition or superposition of organs may occur without the intervention of any such operations. This will be the more readily conceded when it is remembered that the phyllotaxis of leaves not unfrequently varies on different branches of the same individual tree, and that a similar variation in the flower would at once disturb the customary alternate arrangement. Coalescence of the vascular bundles in an unusual manner, and an irregular disposition of these cords have also been considered to bring about deviations from the rule of alternation, but in general the formation of the cords is subsequent to that of the growing points or mamelons.

Adhesions, accompanied by displacements, occasionally produce similar deviations, the nature of which is usually easily detected.

=Co-relation.=--The importance of this subject first prominently brought into notice by Geoffroy St. Hilaire gains in force daily. Rarely is a malformation an isolated phenomenon, almost always it is a.s.sociated, from the operations of cause or effect, with some others. Instances of this co-relation have been cited in the preceding pages, and many more might have been mentioned, had the consideration of the relationship between form and function formed part of the plan of this volume. A change in itself slight, often acquires importance from its a.s.sociation with other alterations. This is particularly well seen in the case of the receptacle. Let an ordinarily concave thalamus remain, from defective development, flat, and how great the change in the appearance of the flower. Let the usually contracted receptacle be lengthened, and the whole aspect of the flowers so affected is altered to such an extent that, were their history not known, botanists would have no hesitation in a.s.signing them to widely separate groups in their schemes of cla.s.sification. Peloria, too, of either form, affords excellent ill.u.s.trations of the co-existence of one changed condition with another.

Not only is the form of one set of organs altered, but the number, the relative proportion, and the direction of the other organs of the flower are altered likewise.[562] Not only is the whole symmetry changed, but the physiological operations carried on in the flower undergo corresponding alterations.

There are certain co-relations which do not appear to have hitherto attracted the attention they merit; such, for instance, is that which exists between the particular period at which an organ is developed and its position and form. In normal morphology this has, to some extent, been worked out, as in the case of definite and indefinite, centrifugal and centripetal inflorescences, and in the definite or indefinite formation of shoots, &c.

Other instances may be cited in the frequent co-existence of regular flowers and definite inflorescence, the terminal position of many peloriated flowers, the relationship between indefinite inflorescence and prolongation of the axis, &c.

Again, the simultaneous evolution of the parts of the flower and their consequent verticillate arrangement, are often a.s.sociated with the production of different forms from those characteristic of organs developed in succession, and, in consequence, arranged spirally. In the case of simultaneous development we meet with a repet.i.tion of whorls, as in what are termed hose-in-hose flowers (flores duplicati, triplicati, &c.), and also with cases of peloria. In instances where the organs are formed successively in spiral order, we meet with such changes as median prolification, petalody, and phyllody. All these are alterations which we might antic.i.p.ate from the activity of the growing point being checked at a certain stage in the one case, while it is continuous in the other. This relationship between the definite and indefinite modes of growth and the form of the several organs of the flower, is more constant in reality than it may appear to be from a perusal of the lists of genera in the foregoing pages, in which it was not possible to show sufficiently well the comparative frequency of any given changes in individual plants. Had it been possible to give statistics setting forth the frequency of certain deviations in plants or groups having a particular organisation, as compared with the rarity of their occurrence in other plants of a different conformation, these co-relationships would have been rendered much more evident. A hundred different plants, for instance, may be named in any particular list, of which fifty shall be of one type of structure, and the remainder of another. And the co-relative changes in each fifty may appear to be evenly balanced, but so far is this from being the case, that the frequency of the occurrence of a particular change, in one species in the list, may be so great as far to exceed the instances of its manifestation in all the rest put together. This difficulty is only very partially obviated by the addition of the * to signify especial frequency of occurrence of any given malformation in the plants to whose names it is affixed.

=Compensation.=--But little further need be said on this head. An atrophied condition of one part is generally a.s.sociated with an hypertrophied condition of another, and scarcely a change takes place in one direction, but it is a.s.sociated with an inverse alteration in some other. This principle is not universal, and its application must not be unduly strained. It requires specially to be considered in reference to differences in the degree or kind of functional activity exercised by the organs implicated--points beyond the scope of the present volume.

=Teratology and cla.s.sification.=--Lastly, there remain to be mentioned the bearings of teratology on systematic botany. There are those who would entirely exclude teratology from such matters. It may be expedient to do so when the object sought is one of convenience and facility of determination only, but when broader considerations are concerned, teratology must no more be banished than variation. In most instances the one differs but in degree from the other. If variation affords aid in our speculations as to the affinities and genealogical descent of species and other groups, so does teratology, and in a far higher degree.

Take the characters of exogens as distinct from endogens; even under ordinary circ.u.mstances, no absolute distinction can be drawn between them. There are plants normally of an intermediate character, while, to take exceptional instances, there are exogens with the leaves and flowers of endogens, and endogens whose outward organisation, at any rate, a.s.similates them to exogens. Diclinous or monochlamydeous plants owe their imperfect conformation to suppression, and may become structurally complete by a species of peloria. Structurally hermaphrodite flowers become unis.e.xual by suppression, or are rendered incomplete by the non-development of one or more of their floral whorls.

Hypogynous flowers become perigynous by adhesion, or by lack of separation; perigynous ones become hypogynous by an early detachment from the receptacle that bears them, or by the arrested development of an ordinarily cup-like receptacle.

How the relative position of the carpels and the calyx may be altered has already been alluded to, as has also the circ.u.mstance that while it is common to find an habitually inferior or adherent ovary becoming superior or free, it is much more rare to find the superior ovary adherent to the receptacle or to the calyx.[563] Regular and irregular peloria, too, serve to show how slight are the boundaries, not only between different genera, but also between different families.

While, therefore, teratology may be an unsafe guide in strictly artificial schemes, it is obvious that its teachings should have great weight in all philosophical systems of cla.s.sification.

The questions will constantly arise, does such and such a form represent the ancestral condition of certain plants? Is it a reversion to that form? or is it, on the other hand, the starting point of new forms?

Such questions cannot receive at present any satisfactory answer, but the evidence we have seems to indicate that pre-existing forms were simpler, and less specialised in structure than those now existing, and hence if we meet with malformations of a simple kind, we may consider them as possible reversions; while, if they present features of increased complexity, and more sharply defined differentiation, we may a.s.sume them to be evidences of a progressive rather than of a retrogressive tendency.

That monstrosities so called may become the starting points of new forms is proved by circ.u.mstance that, in many cases, the peculiarities are inherited so that a new "race" is produced and perpetuated: and if a new race, why not a new species? The difference is one of degree only.

FOOTNOTES:

[553] See Clos., 'Bull. Soc. Bot. Fr.,' 1856, vol. iii, p. 679.

[554] 'Theorie de la Feuille,' p. 26.

[555] An additional ill.u.s.tration of this may be cited, which has been brought under the notice of the writer by Dr. Welwitsch recently, and in which some of the leaflets of the pinnate leaf of a species of _Macrolobium_ were absent, and their place supplied by flowers arranged in cymes.

[556] The presence of a bud at the extremity once considered to be an absolute distinction between branch and leaf, which latter never forms a bud exactly at the apex--is invalidated by the case of the Nepaul barley, p. 174.

[557] 'Journ. Linn. Soc.,' vol. x, p. 103 _et seq._

[558] See also the receptacular tube (ovary?) of _Baeckea_ bearing stamens, see p. 183. It would be natural to see stamens springing from the receptacle but not from the ovary.

[559] In _Pa.s.siflora_ the organogeny of the flower clearly shows the truth of this a.s.sertion, as was indeed shown by Payer and Schleiden.

[560] See Payer, 'Organ. Veget.'

[561] It must, however, be borne in mind that no true leaf-organ has yet been seen with a bud at its exact apex (unless it be the nepaul barley), while in the case of an axial organ such a position of the bud is constant. The nearest approach is in the case of impari-pinnate leaves in which the terminal leaflet is jointed to the common rachis, and in the leaves of some _Meliaceae_ which continue to push forth new leaflets even after the leaf has attained maturity.

[562] A singular instance of co-relation was shown by Mr. Saunders at the Scientific Committee of the Royal Horticultural Society, February 16th, 1868, in a hyacinth with perfectly green, long, tubular, erect, not horizontally spreading flowers.

[563] An ill.u.s.tration of this latter nature in the case of a cherry, which was surmounted by the calyx lobes, precisely as in the case of a pomaceous fruit, has been given at p. 424, _adnot._

APPENDIX

DOUBLE FLOWERS.[564]

In ordinary language, the epithet double flowers is applied to flowers of very varied structural conformation. The most common conditions rendering a flower double, in the popular acceptation of the term, are subst.i.tutions of petals or petal-like bodies for stamens and pistils, one or both. (See Petalody, p. 283.) Another very common mode of doubling is brought about by a real or apparent augmentation in the number of petals, as by multiplication, fission, or chorisis. (See pp.

66, 343, 371, 376.) Sometimes even the receptacle of the flower within the outer corolla, divides, each subdivision becoming the centre of a new series of petals, as in some very luxuriant camellias and anemones.

The isolation of organs which, under ordinary circ.u.mstances, are united together, is another circ.u.mstance, giving rise, in popular parlance, to the use of the term double flower. (See Adesmy, Solution, pp. 58, 76, 82.) Prolification is another very frequent occurrence in the case of these flowers, while still other forms arise from laciniation of the petals, or from the formation of excrescences from the petals or stamens, in the form of supplementary petal-like lobes. (See Enation, p.

443.)

As these matters are all treated of under their respective headings, it is not necessary to allude to them again in detail. It may be well, however, to allude, in general terms, to the causes which have been a.s.signed by various writers for their formation, and to the means which have been adopted by practical experimenters to secure the production of the flowers often so much esteemed by the florist. It must be admitted that, in spite of all that has been written on the subject, but very little is known about these matters. In the case of the stock the following means have been adopted by cultivators in order to obtain plants bearing double instead of single flowers. There is first the crossing of single flowers with double ones, effected by planting a double-flowered plant in proximity to a single-flowered one; but this, it is obvious, could lead to no important results, since the double flowers, having no pollen, could not possibly influence the seed, which is borne only by the single-flowered plants. Another plan is the degustation of the buds, that is to say, the chewing of the well-formed buds; it is held that the single plants can be recognised by their sweeter taste and greater consistence, and may thus be weeded out; but there is at least the disadvantage attending this method, that the plants, single as well as double, must all be grown up to the period when these buds are tolerably well advanced. A third method which has been adopted is, that of sowing the seeds at a particular lunar epoch, great confidence being placed in the plan of planting them during the last quarter of the moon, but such confidence is found to be misplaced.

The plan of removing the stamens has had its supporters, but as this must be done at an early stage of development, and could only influence the result by diverting the vital force which would be expended in the maturation of the pollen, to the perfecting of the seeds, it is obvious that the plan is impracticable for all ordinary purposes, even if in any degree efficient, which from the plasticity of vegetable development, and the faculty of doubling which is inherent in the stock family, is not at all improbable. Still another mark, the presence of a fifth petal in the single or seed-bearing flower, has been held to indicate the a.s.surance of obtaining a crop of double-flowered plants from seeds saved from flowers possessing this peculiarity. To a certain extent, doubtless, this expectation would be realised, owing to the plasticity and inherent quality just alluded to, but the proportion would be too small for any useful practical purpose.

"The gardeners of Erfurt," observes M. Chate, who has written a book[565] on the subject, in which he makes known a means of obtaining double-flowered stocks founded on more than fifty years' practice in his family, "have, for a long time, to a certain extent monopolised the sale of seeds of these plants. To obtain these seeds, the Erfurt gardeners cultivate the flowers in pots, and place them on shelves in large greenhouses, giving them only sufficient water to prevent them from dying. So cultivated the plants become weakened, the pods shortened, and the seeds less numerous, and better ripened; and these seeds give from 60 to 70 per cent. of double flowers.

"The seeds from these plants are said to be mostly of an abnormal shape, which is so striking that experienced cultivators are able to separate those which would furnish double flowers from those which would produce single ones."

M. Chate's method, which he calls the French one, gives still greater results, viz.: 80 per cent. of double flowers, and these produced by very simple means. "When my seeds," he observes, "have been chosen with care, I plant them, in the month of April, in good dry mould, in a position exposed to the morning sun, this position being the most favourable. At the time of flowering I nip off some of the flowering branches, and leave only ten or twelve pods on the secondary branches, taking care to remove all the small weak branches which shoot at this time. I leave none but the princ.i.p.al and the secondary branches to bear the pods. All the sap is employed in nourishing the seeds thus borne, which give a result of 80 per cent. of double flowers. The pods under this management are thicker, and their maturation is more perfect. At the time of extracting the seeds the upper portion of the pod is separated and placed aside, because it has been ascertained that the plants coming from the seeds situated in this portion of the pod, give 80 per cent. of single flowers. They yield, however, greater variety than the others. This plan of suppressing that part of the pod which yields single flowers in the largest proportion, greatly facilitates the recognition of the single-flowered plants, because there remains to be eliminated from among the seedlings only from 10 to 15 per cent.

This separation of the single from the double-flowered plants, M. Chate tells us is not so difficult as might be supposed. The single stocks, he explains, have deep green leaves (glabrous in certain species), rounded at the top, the heart being in the form of a shuttlec.o.c.k, and the plant stout and thickset in its general aspect, while the plants yielding double flowers have very long leaves of a light green colour, hairy, and curled at the edges, the heart consisting of whitish leaves, curved so that they enclose it completely. Such is the substance of M. Chate's method of securing so large a proportion of double-flowered plants, and then of separating them from the remaining single ones--a method which commends itself to the good sense of the intelligent cultivator."[566]

Signor Rigamonti, a great cultivator of pinks, a.s.serted that he was able to distinguish double from single-flowered pinks, in the seedling state.

According to this gentleman, those seedlings which produce three cotyledons in a whorl in place of two, form double flowers. In the case of _Primula sinensis_ the same results occurred. Some had three leaves in a ring, others two; most had the leaves standing one over the other as usual. These were divided into three sets, and when they flowered, the first lot were all double, the second semi-double, the third single.

But these statements have not been confirmed by other observers; and the writer can safely a.s.sert that seedling pinks occasionally produce three cotyledons, and subsequently single flowers. He has never observed a double flower under these circ.u.mstances, though it is true his experience in this matter has been but small.

A writer in Otto's 'Gartenzeitung,' considers that double flowers are a consequence of dryness of soil and atmosphere, and not of a luxurious soil, rich in nutritious matter, having arrived at this conclusion from an observation of the following circ.u.mstances:

"Fifty years ago we saw _Kerria j.a.ponica_ in a hothouse with single flowers. Twenty years later we met with it in several gardens, in the open air, but always with double flowers. At this time we were a.s.sured that single-flowered plants were no more to be found in the whole of Europe, and botanists forming herbaria offered considerable sums for a branch of _K. j.a.ponica_ with single flowers. We were requested to take the plant in hand for the purpose of inducing it to produce single flowers. We were advised to plant it out in a rich soil, which was done, but, by chance, the situation was sloping, consequently it did not retain moisture, and all the flowers produced for several years in succession were double. Shortly after, the captain of an English ship again brought plants bearing normal flowers from j.a.pan, which were soon spread over the continent, and of which we received one plant. After three years all the young plants raised from cuttings were double-flowered.

"In the year 1820 we several times visited a garden in the neighbourhood of Vienna, well known on account of its plant culture. The gardener there possessed an immense plant of _Camellia j.a.ponica_ with single flowers, and some small plants raised from this by cuttings, but no other variety of camellia. He fertilised the flowers with their own pollen, harvested seeds, which he sowed, and the plants raised from them were placed in an extremely dry, lofty conservatory, where, after some years, instead of producing single flowers, they all produced double ones. The seedlings and mother plant were planted in one and the same kind of earth, and some of the flowers on the old plant also showed an inclination to become double.

"This, at that time, to us, enigmatical phenomenon, was kept in mind until we had an opportunity of inst.i.tuting comparisons between the climate of j.a.pan and China and our own, and we then concluded that in the case of a plant imported from thence, and exposed to such different climatical influences, the origin of the greater or less imperfection of its s.e.xual organs was probably owing to this change, as we had experienced in _Kerria_ and _Camellia_; and that the sterility of many other exotic plants might be attributed to the same cause. The difference in the climatical relations of j.a.pan and Europe is very considerable. In j.a.pan, previous to the new growth of _Kerria_ and _Camellia_, a rainy season of three months' duration prevails; in Europe, on the contrary, dry winds prevail especially in the eastern part, where our plains are often transformed into deserts. Is it, therefore, remarkable that a plant introduced from j.a.pan into Europe, exposed to the influences of this great diversity of climate, should produce imperfect s.e.xual organs incapable of further propagating the plant from seeds? A rich soil, with the necessary amount of moisture, will never engender double flowers."[567]

Mr. Darwin[568] describes a peculiar form of _Gentiana Amarella_, in which the parts of the flower were more or less replaced by compact aggregations of purple scales in great numbers. A similar condition is, indeed, not uncommon in this plant, and, as Mr. Darwin also remarked, on hard, dry, bare, chalky banks, thus bearing out the views expressed by the writer in the 'Gartenzeitung' just cited. Some double flowers of _Potentilla reptans_ found growing wild near York, and transmitted to the writer by a correspondent, were observed growing along a high wall, in a dry border, close to a beaten path, bordering on a gravel pit, others were found on a raised bank, which, from its elevation and exposure to the sun, was particularly dry.

On the other hand, the double-flowered _Cardamine pratensis_, which is occasionally found in a wild state, always grows in very wet places.

Of late years a remarkable double-flowered race of _Primula sinensis_ has been obtained. In particular, Messrs. Windebank and Kingsbury, of Southampton, have succeeded in raising a set of plants in which the flowers are very double and very attractive in a florist's point of view. The corollas in these flowers are not merely duplicated, but from their inner surface spring, in some cases, funnel-shaped or tubular petals (p. 315), so regular in form as quite to resemble a perfect corolla. These tubes are attached to the inner side of the tube of the corolla, in the same way as are the stamens, these latter organs being, it appears, absent. The carpels are present, but open at the top, and bear numerous ovules, hence it was at first surmised that these plants were obtained and perpetuated, by the application of pollen from single flowers to these double-flowered varieties.