[291] 'Flora,' 1856, p. 712.

[292] 'Trans. Linn. Soc.,' vol. xxvi, p. 37.

[293] 'Bull. Soc. Bot. France,' 1862, vol. ix, p. 36, tab. i, and also p. 291.

[294] Ibid., 1857, vol. iv, p. 761.

CHAPTER II.

METAMORPHY OF THE FLORAL ORGANS.

One of the main arguments adduced by Goethe and others in support of the now generally received doctrine of the essential morphological ident.i.ty of the various whorls of the flower is derived from the frequent appearance of one organ in the guise of another. The several parts of the flower become, as it is said, metamorphosed; sometimes the change is complete, while at other times there may be every conceivable intermediate condition between one form and another. The sense in which the terms metamorphosis, subst.i.tution, transformation, and the like, are herein used has already been explained. For the convenience of arrangement, metamorphosis of the parts of the flower may be divided into several subdivisions, according to the particular organ affected, and according to the special kind or degree of change manifested, the main subdivisions being here cla.s.sed as Sepalody, Petalody, Staminody, and Pistillody.

=Sepalody of the petals.=--This change, spoken of by most authors as retrograde metamorphosis of the petals into sepals, or as a subst.i.tution of sepals for petals, is obviously a condition that is in most cases hardly distinguishable from virescence of the corolla, or from multiplication of the sepals. Nor is this of much consequence unless there are some special structural features which render the discrimination a matter of importance, in which case the difficulty is generally easily surmounted. The flower of the Saint-Valery Apple may perhaps be cited under this head. In the flower in question there are neither stamens nor petals, unless the second or inner of sepals be considered as sepaloid petals (fig. 152).

[Ill.u.s.tration: FIG. 152.--Flower of St. Valery apple, with sepaloid petals.]

M. Alph. de Candolle[295] describes an instance in _Primula Auricula_ in which the corolla had a.s.sumed the appearance of the calyx, but neither calyx nor corolla in this case possessed perfect stomata.

This malformation is much less common than the converse one of calycanthemy. Many of the recorded instances of so-called metamorphosis of the parts of the flower to sepals have occurred in monocotyledonous plants, or others in which the calyx and corolla are of the same colour, and const.i.tute what is frequently termed the perianth; and as this is usually brightly coloured (not green) it is more convenient to group the metamorphoses in question under the general term Petalody, which thus includes all those cases in which the organs of the flower appear in the form of coloured petal-like organs, whether they be true petals or segments of a coloured perianth. As the morphological difference between the organs is one of position merely, there is little objection to be raised to this course, the less so as the term petalody merely conveys an idea of resemblance and not of absolute ident.i.ty.

Petaloid coloration of the ordinary leaves, or of the bracts, is mentioned under the chapter relating to colour.

=Petalody of the calyx--Calycanthemy.=--As with the bracts, so the calyx in certain instances is naturally coloured, as in _Delphinium_, _Tropaeolum_, and others. In _Mussaenda_, _Calycophyllum_, _Usteria_, &c., one or more of the calyx lobes become enlarged normally. Considered teratologically, petaloid coloration of the sepals is either general or partial; in the latter case the nerves retain their green colour longest. There is in cultivation a variety of the primrose called _Primula calycanthema_, in which the upper part of the calyx becomes coloured, so that the flower seems to have two corollas placed one within the other; a similar thing happens in _Mimulus_, in which plant, as the calyx is permanent while the corolla is deciduous, the coloured calyx is a great advantage in a horticultural point of view. Morren[296]

says that in order to produce the fine colour of the calyx of _Primula officinalis_ (var. _smaragdina_) the Belgian gardeners cut away the corolla in a very early stage, and that in consequence the colouring matter proper to the corolla is developed in the tube of the calyx, the edges of the limb remaining green, the middle of the limb being purple (_Primula tricolor_).

[Ill.u.s.tration: FIG. 153.--Flower of _Mimulus_, with petaloid calyx.]

Under this head may be mentioned the occurrence of tubular sepals in place of the ordinary flat ones in _h.e.l.leborus olympicus_; only two of the sepals were thus affected in a specimen recently observed--a third exhibited an intermediate condition.

The normal coloration of the calyx occurs most frequently in polysepalous calyces; teratological coloration, on the other hand, occurs especially in gamosepalous flowers. This a.s.sertion is borne out by the frequency of the change in the plants already mentioned, and also in the following:--_Campanula persicifolia_, _Anagallis arvensis_, _Gloxinia_, _Syringa persica_,[297] _Calceolaria_, _&c. &c_. In the last-named plant one or more of the lobes of the calyx may frequently be seen replaced by a slipper-like petal.

Among polysepalous plants petaloid sepals have been observed in _Ranunculus auricomus_, _Rubus caesius_, _&c._ Fleischer also describes a case of this kind in _Carum carui_.[298]

It will be seen from the above that in the majority of cases there is no real metamorphosis or subst.i.tution of petal for calyx, but simply an alteration in colour; nevertheless, a change in form may accompany a change of colour: this happens especially if there has been any displacement of organs. Thus, if, in an orchidaceous plant, a sepal be displaced from any cause, or a petal be twisted out of its natural position to occupy the place of an absent sepal, that petal will be sepal-like in form, and _vice versa_.

=Petalody of the stamens.=--A petaloid condition of the stamens is one of the commonest of all malformations. A large number of so-called double flowers (flores pleni)[299] owe their peculiar appearance to this circ.u.mstance.

It is necessary to distinguish carefully this petaloid development of the stamens from the corresponding condition of the pistils, and from that kind of doubling which is a result of multiplication of the corolla, as in _Datura_, _Campanula_, _Primula_, &c. (flores duplices, triplices, &c.), or from that produced by true median prolification (flores geminati, &c.).

In cases of true petaloid development of the stamens there are usually numerous intermediate forms between that of the true petals and that of the perfect stamens; indeed, in _Nymphaea_, _Canna_, and in some other plants, such a transition occurs normally. Petalody of the stamens may occur either without material change in the flower or it may exist in combination or in conjunction with an increased development of parts (Multiplication), or with a similar change in the carpels, and it is either partial or complete.

Among the flowers in which petaloid development of the stamens happens most frequently may be mentioned those in which the calyx is normally coloured, as in _Nigella damascena_, _Aguilegia_, and _Delphinium_.

M. Alph. de Candolle, in the 'Neue Denkschriften,' 1841, described and figured a singular form of _Viola odorata_, known under the name of "Bruneau," in Switzerland, in which the stamens are absent, and their place supplied by a second row of petals, within which is a third series of petals, representing, says M. de Candolle, the inner row of stamens that theory suggests should exist in the natural condition. Moreover, the carpels in this variety are five in number instead of three. In _Erica Tetralix_ the corolla may not unfrequently be found divided to the base into its const.i.tuent petals, and the place of the stamens occupied by a series of petal-like structures entirely dest.i.tute of anther.

In monocotyledonous flowers, especially those with a coloured perianth, the subst.i.tution of segments of the perianth for stamens occurs not unfrequently. M. Seringe has observed this in the stamens of _Lilium Martagon_, and there is in cultivation a variety of the white lily, _Lilium candidum_, sometimes called the double white lily, in which the segments of the perianth, in place of being arranged in two rows, are greatly increased in number, and disposed in a spiral manner. In these flowers, not only are the stamens and pistils thus modified, but also the upper leaves of the stem. In so-called double tulips there is likewise a replacement of stamens by coloured segments of the perianth, but this happens generally in connection with an increase in the number of organs. Moquin-Tandon remarks having seen in a garden in the environs of Montpelier a tulip, the stamens of which showed all possible stages of transition between the form proper to them and that of the perianth.

The pistil in this case was transformed into several small leaves.

Similar appearances have been observed in Iris, Hyacinths, Narcissus, Colchic.u.m, and Crocus. M. Fournier[300] describes a flower of _Narcissus Tazetta_ from within the normal perianth of which sprang a second one, equally provided with a cup and occupying the s.p.a.ce usually filled by the stamens. Flowers of _Narcissus poeticus_ may also be met with in which the stamens are replaced by six distinct segments exactly resembling those of the perianth in miniature.[301]

[Ill.u.s.tration: FIG. 154.--Double columbine, _Aquilegia_--petalody of the filament.]

From an examination of these flowers it becomes evident that petalification is brought about in different flowers in different ways; sometimes it is the filament which becomes petaloid, sometimes the anther-lobes, while at other times it is the connective which a.s.sumes the appearance of petals.[302] For instance, in _Solanum tuberosum_, _S. Dulcamara_, in _Anagallis_, in _Fuchsia_, and some other plants, the anther-lobes themselves become petaloid, while the filament remains unchanged.

In gardens two distinct varieties of Columbine are cultivated, the one in which the filaments are dilated into the form of flat petals almost entirely or quite dest.i.tute of anthers, while in the other the filament is present in its usual form, but the anther is developed in the shape of a tubular hood or spur.

De Candolle[303] observes that in the _Ranunculaceae_ the species of _Clematis_ become double by the expansion of the filament, those of _Ranunculus_ by the dilatation of the anther, and those of _h.e.l.leborus_ by the petal-like development of both filament and anther. In some cases even on the same plant all three modifications may be seen, as in Camellias, some of which may be found with petaloid filaments with anthers on the top, others with the filaments unchanged, but supporting petaloid anthers, while in others it is the connective alone which is petal-like. Where the flower naturally contains a large number of stamens, as in Mallows, Roses, Magnolias, &c., petaloid expansion of the filament is most common, though it is by no means confined to such flowers, the change occurring in _Allamanda cathartica_, _Jasminum grandiflorum_, and many other flowers with few stamens. A similar change in the anther and connective takes place more frequently in flowers where the number of stamens is smaller, but there are of course numerous exceptions to this rule.

In those cases where there is more than one row of stamens, the outermost are most liable to this change: thus in _Saxifraga decipiens_, as shown by Ch. Morren,[304] the outer series of stamens--those opposite to the sepals--become first affected, and, at a more advanced stage, the inner row also; and this is the case in most flowers that have their stamens in two rows. Occasionally it happens that an outer series of stamens is abortive, or wholly suppressed, while the inner row becomes petalodic; this was the case in some flowers of _Lilium auratum_ lately exhibited by Messrs. Veitch.

Those flowers in which only a portion of the stamens undergo this change are called semi-double, while in other cases that will be hereafter mentioned, not only are the stamens thus rendered petaloid, but their number is also augmented, as in most double roses, pinks, anemones, poppies, &c.

In some double flowers, in which the stamens a.s.sume more or less completely the appearance of petals, a singular appearance is afforded by the presence of four wing-like processes emanating from the central filaments, two on each side, so that the arrangement may be compared to two sheets of paper folded in the centre and adherent in that situation, though perfectly separate elsewhere, except sometimes at the top, where they form a sort of hood. This change results from an imperfect petalody of the anther; the two wings on each side of the central vascular cord represent the front and back walls of an anther lobe, or rather of that portion of the anther which, under ordinary circ.u.mstances, produces pollen. In the malformed flowers no pollen is formed, at least in the more complete states of the malformation, but the walls of the anther lobe become preternaturally enlarged, and petaloid in texture and appearance. This change occurs in some semi-double rhododendrons and azaleas, in crocuses, and in a species of violet found at Mentone by Mr.

J. T. Moggridge.

There are numerous intermediate forms wherein the wing-like processes may be traced all the way along the filament till they ultimately lose themselves in the anther-lobes, with which they become continuous. In some cases, as in _Crocus_ and _Rhododendron_, this is shown even more clearly by the existence of two perfect pollen-sacs or quarter-anthers, the remaining portions being petaloid and continuous with the dilated filament. Not unfrequently these semi-petaloid stamens adhere to the fronts of the petals, and then it appears, at a first glance, as if three organs were stuck together, one in front of another, while in reality there are but two.[305] (See _ante_, p. 35, fig. 12.)

[Ill.u.s.tration: FIG. 155.--Four-winged filaments of _Rhododendron_.]

The change in the anther, above alluded to, must not be mistaken for that far more common one in which only a small portion of the anther becomes petaloid, forming a sort of lateral wing or appendage to the polliniferous portion, as happens normally in _Pterandra_, and is common in some double fuchsias. In this latter instance there is but a single wing, and the nature of the case is obvious.

Double flowers of _Orchidaceae_ generally arise from petalification of the filaments, with or without other coincident changes. What makes double flowers in this order the more interesting is the development, in a petaloid condition, of some or all of those stamens which under ordinary circ.u.mstances are wholly suppressed, so that the morphological structure of the flower, at first a matter of theory, becomes actually realised. Fig. 156 is a diagram showing the presence of two additional labella within the ordinary one in a species of _Catasetum_, and representing two petaloid stamens, thus evidently completing the outer staminal whorl, of which there is usually but a single representative (see Peloria, Multiplication, Prolification). In some of these double orchids it is, however, necessary not to confound a petaloid condition of the existing column with the development of usually suppressed stamens in a petaloid form. Thus, in _Lycaste Skinneri_ the column is frequently provided with two petal-like wings, which might readily be supposed to be two stamens of the inner whorl adherent to the column; a little attention, however, to the relative position of these advent.i.tious wings is generally sufficient to enable the observer to ascertain the true nature of the appearance.[306]

[Ill.u.s.tration: FIG. 156.--Diagram of flower of _Catasetum_, with two labella.]

Some forms of duplicate or hose in hose corollas are apparently due, not so much to the formation of a second corolla within the first, as to the presence of an inner series of petal-like stamens, which, by their cohesion, form a second pseudo-corolla within the first. The staminal nature of this pseudo-corolla is inferred from the occasional presence of anthers on it.[307] In _Datura fastuosa_, as well as in _Gloxinia_, a pseudo-corolla of this kind sometimes occurs with the addition of a series of petaloid stamens attached to its outer surface.[308]

When the petalody specially affects the anther-lobes, as in _Arbutus_, _Petunia_, _Fuchsia_, _&c._, the venation of the petal-like portion is very frequently laminar, thus tending to show that the anther is in such cases really a modification of the blade of the leaf; but as, on the other hand, we often find petal-like filaments bearing pollen-sacs on their sides, it is clear that we must not attribute the formation of pollen to the blade of the leaf only, but we must admit that it may be formed in the filament as well.[309]

[Ill.u.s.tration: FIG. 158.--Portion of a double columbine (_Aquilegia_), showing petalody of the connective.]

[Ill.u.s.tration: FIG. 159.--Petaloid stamens, _Hibiscus_.]

Petalody of the connective is of less frequent occurrence than the corresponding change in the other portions of the stamen. It may be seen in some forms of double columbine,[310] in which the connective forms a tubular petal or nectary, and in double petunias and fuchsias. When it occurs, the true anther-lobes are usually atrophied, and little or no pollen is formed.

An occurrence of this nature in _Tacsonia pinnatistipula_, in conjunction with the partial detachment of the stamens from the gynoph.o.r.e, led Karsten to establish a genus which he called _Poggendorffia_.[311]

From the subjoined list of genera in which petalody of the stamens, in some form or other, has been observed, it will be seen that it happens more often in plants with numerous distinct organs (Polypetalae, Polyandria, Polygynia, &c.) than in other plants with a smaller number of parts, and which are more or less adherent one to the other. The tendency to petalification is, moreover, greater among those plants which have their floral elements arranged in spiral series, than among those where the verticillate arrangement exists; and in any given flower, if the stamens are spirally arranged while the carpels are grouped in whorls, the former will be more liable to petalody than the latter, and _vice versa_. It has been before remarked, that this condition is far more common in plants whose petals, &c., have straight veins, like those in the sheath of a leaf, than in those the venation of which is reticulate, as in the blade of the leaf. It must also be remembered that in the same genus, even in the same species, different kinds of doubling occur. Familiar ill.u.s.trations of this are afforded in the case of anemones, columbines, fuchsias, and other plants.

The existence of "compound stamens" in some flowers, as pointed out by Payer, and others, and the researches of Dr. Alexander d.i.c.kson, confer additional importance on the subject of petalody, and necessitate the examination of double flowers with special reference to these compound stamens, and to the order of their development.[312] The presence of these compound stamens affords a satisfactory explanation of the appearance in some double _Malvaceae_, wherein the tufts of advent.i.tious petals are very liable to be mistaken for buds, produced by axillary prolification in the axils of the petals, but which are in reality compound and petaloid stamens. At other times, however, true axillary prolification exists in these flowers; but then the supplemental florets have always a calyx, which is wanting in the other instances.

Petalody of the stamens has been met with most frequently in the following genera:

*Ranunculus!

*Anemone!