Chapter 7

Fig.52.—Inflorescence ofPolyanthus, bearing a tuft of leaves at the top of the scape intermixed with the flowers.

Median floral prolification of the inflorescence, wherein a new inflorescence projects beyond the primary one, is not uncommon in plants having their flowers arranged in close heads or umbels, as in the commonwild celery and otherUmbelliferæ.[110]I have also met with it inTrifolium repens, in the umbellate variety of the common primrose, and in the scarlet geranium. Engelmann cites it inTriticum repens, Roëper inEuphorbia palustris.[111]

Lateral foliar prolification of the inflorescenceis of more common occurrence than the preceding. I have met with it, amongst other plants, frequently inBrassica oleracea,Pelargonium zonale,Scabiosa,Bellis, and many other composites, also inLeguminosæ, e.g.Lupinus,Trifolium,Coronilla, &c. Prof. Oliver forwarded me a specimen ofEuphorbia geniculatain which, in addition to other changes, there was a series of stalked buds bearing tufts of green scales, but without any trace of stamens or pistil; these adventitious buds occurred within the ordinary involucre of the plant, between it and the stamens. The pistil was unaffected in some cases, while in some others it was entirely wanting, the gynophore being surmounted by a cup-like involucre, divided into three acutely pointed lobes, each with a midrib; these encircled a series of stalked involucels, as before, and among which were scattered a few stamens, some perfect, others partially frondescent.

In a specimen ofScrophularia nodosaexamined by me one of the lateral buds on each of the cymes was represented, not by a flower, but by a tuft of leaves, the other buds being unchanged. As the inflorescence was much contracted in size, the appearance of the whole plant was greatly changed.

Many of the instances of so-called viviparous plants,e.g.,Polygonum viviparum, may be cited under this head.[112]Many species ofAllium,Lilium,Saxifraga,Begonia,Achimenes, normally produce leaf-buds or bulbs in the inflorescence; so, too, leafy shoots are sometimesfound inAlisma natans,Juncus uliginosus,Chlorophytum Sternbergianum, &c. As an accidental occurrence, a similar thing has been noticed inLychnis coronaria,Phaius grandifolius,Oncidium cebolleta,Epidendrum elongatum,[113]&c. &c.

Here, too, may be mentioned those cases wherein a leaf-bud is found upon the surface of the so-called inferior ovary; generally a leaf only is found, but a leaf-bud may also originate in this situation, and in either case the inference is that the ovary is, in part at least, made of the dilated and hollowed axis. Leaves may occasionally be found in this way on the so-called calyx-tube or on the inferior ovaries of roses, pears, apples,Pereskia,Cratægus tanacetifolia, &c.

The fruits ofOpuntia Salmaniaand ofO. fragilis('Bull. Soc. Bot. France,' vol. i, p. 306; vol. v, p. 115) have been observed to form small fruit-like branches around their summits. This circumstance is more fully treated of in the succeeding chapter relating to Heterotaxy.

Lateral floral prolification of the inflorescence.—This, which is termed by Engelmann Ecblastesis foliorum sub floralium,[114]is much the most common of all these deviations, and it is met with in every degree, from the presence of a single supernumerary flower in the axil of a bract to the existence of a small cluster or panicle of such flowers.

Fig.53.—Lateral prolification in inflorescence ofPelargonium.

It is common in theAnemone coronariaandhortensis, also in the common scarletPelargonium(fig. 53). It has been frequently recorded inPoterium sanguisorba, and inSanguisorba officinalis, and is especially common inUmbelliferæ,Dipsacaceæ, andCompositæ; a familiar illustration in the latter order is afforded by the hen-and-chicken daisy. In some species of Compositæ, indeed,it is a normal and constant occurrence, while in other cases, such asFilago germanica, usually described as proliferous, there is not, strictly speaking, any prolification, for the branching of the stalk takes place below the inflorescence, and the branches originate from the axils of ordinary leaves, not from the floral leaves or bracts.Convolvulus Sepiumis very commonly subject to the production of flower-buds from the axils of the floral leaves. The several species of Plantain (Plantago) seem very liable to this and similar changes. Schlechtendal[115]gives a summary of the various kinds of malformation affecting the inflorescence inPlantago, and divides them into five groups, as follows:—1st, bracteate, wherein the inferior bracts are quite leaf-like, as is frequently seen inPlantago major. 2nd, roseate; bracts leafy in tufts or rosettes, without flowers, as in the so-called rose plantain, common in old-fashioned gardens in this country. 3rd, polystachyate; spike-branched, bearing other spikes in the axils of the bracts, as inP. lanceolata,P. maritima, &c. 4th, proliferous, where the flower-stalk bears a rosette, a spike, or ahead with other rosettes. 5th, paniculate, in which the inflorescence has become a much-branched pyramidal panicle, covered with little bracts, and with very rudimentary flowers.[116]The first two groups belong rather to frondescence of the bracts; but with regard to the whole of them it will easily be surmised that intermediate forms occur, linking one group to the other, and defying exact allocation in either. Thus, in the borders of richly cultivated fields in the neighbourhood of London I have frequently gathered specimens ofPlantago majorwith a branched spike provided with large leafy bracts, the branches of the spike being but little less in diameter than the ordinary single spike. These specimens would therefore seem to be intermediate between Schlechtendal's bracteate and polystachyate divisions. Wigand[117]also describes an anomalous specimen ofPlantago majorsimilar to those just mentioned, but having small lateral spikes in place of large ones. The instance quoted from Professor Braun would fall under the roseate section, as would also that of Kirschleger, though we are expressly told that the tuft of leaves in this last case was not developed until after the ripening of the seed-vessel. One of the characters of the roseate group, according to Schlechtendal, is the absence of flowers, but most persons who have had the opportunity ofwatching the growth of the rose plantain must have observed the occasional production of flowers, sometimes stalked, in the axils of the leafy bracts, and at the same time have noticed that the internodes become elongated, so that an approach is made to the ordinary spike-like form of the inflorescence. The proliferous group would include such specimens as that ofP. lanceolatamentioned by Dr. Johnston,[118]wherein were several spikes, some sessile, others stalked and pendent, the whole intermixed with leaves and disposed in a rose-like manner. I have myself gathered specimens of this nature, occurring in the same plant, at Shanklin, Isle of Wight (fig. 56).

Fig.54.—Plantago major, with panicled inflorescence.

Fig.55.—Inflorescence ofPlantago major, with bracts partly replaced by leaves and spike branched.

Fig.56.—Inflorescence ofPlantago lanceolata, bearing a tuft of leaves and flowers at the end of the flower-scape.

It is rather singular that each species ofPlantagoseems to have its own perverse mode of growth; for instance, the bracteate, polystachyate and paniculate forms are almost exclusively confined toP. major, the roseate form toP. media, the proliferous form toP. lanceolata.

The instances wherein flower-buds originate from the surface of an inferior ovary, as in those cases where the top of the stem is dilated so as to form part of the fruit, would be properly classed under the head of prolificationof the inflorescence. As, however, there is still some difference of opinion as to the correct morphological interpretation to be put on some of these cases, it has been thought better to include them under the head of heterotaxy than of prolification.

Fig.57.—Branched inflorescence ofReseda luteola.

Some of the cases of prolification of the inflorescence resulting in a branching of an ordinarily simple inflorescence, as inReseda luteola(fig. 57), might equally well be placed with fission or multiplication of the axile organs. Branched spikes of this character are not so common among Orchids as might be expected.Professor Reichenbach enumerates a few instances in the Report of the International Botanical Congress of London, 1866, p. 121, and the same author gives an illustration in his 'Orchidographia Europœa,' tab. 150.

In Grasses, as indeed in other plants with a spicate inflorescence, this change occurs not unfrequently. The common Ray Grass (Lolium) is especially subject to the change in question, and among cultivated cereals, maize and wheat occasionally show this tendency to subdivision. One variety of the latter grain is cultivated in hot countries under the name of Egyptian wheat—Triticum vulgare, var.compositum.

Prolification of the inflorescence has been most frequently observed in the following genera:

Leafy.Floral.RanunculaceæRanunculus.Ranunculus!Anemone.Anemone.Cruciferæ.*Brassica!Caryophyllaceæ.Lychnis!Dianthus!Geraniaceæ.*Pelargonium!*Pelargonium!Leguminosæ.*Trifolium!Trifolium!Lotus!Lotus!Coronilla!Cytisus.Cytisus.Rosaceæ.Poterium.*Pyrus!*Pyrus!*Cratægus!Cratægus!*Rosa.Rosa!Sanguisorba.Philadelphaceæ.Philadelphus.Crassulaceæ.Sempervivum.Echeveria.Crassula.Ficoideæ.?Tetragonia.Cactaceæ.Opuntia.Opuntia.Pereskia.Saxifragaceæ.Saxifraga!Umbelliferæ.Seseli.*Apium!Cnidium.Chærophyllum.Eryngium.Eryngium.Silaus.Heracleum!Heracleum!Hydrocotyle.Hydrocotyle.Daucus.Carum.Selinum.Angelica!Conium.Astrantia.Œnanthe.Œnanthe.Begoniaceæ.Begonia!Valerianaceæ.Valeriana.Dipsacaceæ.*Scabiosa!*Scabiosa!Knautia!Knautia!Compositæ.*Bellis!Centaurea.Calendula.Calendula.Anthemis.Coreopsis.Apargia.Lampsana.Carlina.Arnoseris.Tragopogon!Tragopogon!Rudbeckia!Senecio!Carlina.Bidens!Pyrethrum.Filago.Hedypnois.Cirsium.Lactuca.Campanulaceæ.Prismatocarpus.Lobeliaceæ.Jasione.Ericaceæ.Azalea!Convolvulaceæ.Convolvulus!Convolvulus!Calystegia!Scrophulariaceæ.Scrophularia!Antirrhinum!Gesneraceæ.Achimenes!Primulaceæ.Primula!Primula!Cyclamen!Cyclamen!Plumbaginaceæ.Armeria.Plantaginaceæ.*Plantago!*Plantago!Polygonaceæ.Polygonum!Euphorbiaceæ.Euphorbia!Urticaceæ.Ficus.Amentaceæ.Corylus!Castanea!Castanea.Coniferæ.*Larix!*Cryptomeria!Taxodium!Pinus.Orchidaceæ.Phaius!Ophrys!Epidendrum!Oncidium!Liliaceæ.*Allium!*Ornithogalum!*Lilium!Amaryllidaceæ.FourcroyaAlismaceæ.Alisma!Palmaceæ.Cocos.Juncaceæ.*Juncus!Restiaceæ.Restio!Restio!Elegia!Elegia!Willdenovia!Willdenovia!Cyperaceæ.Carex.Graminaceæ.Dactylis.*Lolium!Festuca.*Zea!*Triticum!*Hordeum!Secale.Phleum.

In addition to the papers already cited the following works may be consulted with reference to prolification of the inflorescence:

Moquin-Tandon. 'El. Ter. Veg.,' p. 376. Engelmann, 'De Antholysi,' §§ 85–87. Fleischer, 'Missbild. Versch. Cultur. Pflanz.' For figures of Hen and Chicken Daisy (Bellis prolifera). see Lobel, 'Ic.,' 477. Sweert, 'Florileg.,' pl. 98, f. 5. 'Hort. Eystett. Plant. Vern.,' fol. iv, f. i. &c. For similar malformations in marigold (Calendula), see Lobel, 'Ic.,' 553. 'Act. Acad. Nat. Cur.,' vol. x, p. 208. Jaeger, 'Missbilld.,' 192–195. 'Hort. Eystett.,' pl. æstiv. fol. iii, f. i. Klinsmann, 'Linnæa,' t. x, p. 607.For monstrous plantains, in addition to previous citations, see Camerarius, 'Epist.,' p. 261,P. rosea. Matthioli, 'Krauterb,' 245. Lobel, 'Stirp. Advers. Nov.,' p. 128,P. major paniculata.J. Bauhin, 'Hist. Plant.,' i, p. 503b. Ibid., p. 503,a,c,P. major rosea,bracteata paniculata,prolifera, &c. 'Hort. Eystett.,' pl. æstiv., t. vii, f. 2,P. roseaetP. bracteata. Lobel, 'Stirp. Hist.,' p. 162. Dodonæus, 'Pempt.,' 1–4, cap. xxiii, P. major spica multiplex,i.e.paniculata. Gerard, 'Herbal.' Clusius, 'Plant. Rar. Hist.,' lib. v, p. 109–10,Plantago augustifolia Gareti prolifera. Marchand, 'Adansonia,' iv, p. 156.Coniferæ.—Richard, 'Mem. Conif.,' tab. xiii, f. 9. A. Braun, 'Das Individ.,' 1853, p. 65. De Cand., 'Organogr.,' tab. xxxvi. Wigand, 'Bot. Untersuch.,' 154. Schlechtendal, 'Bot. Zeit.,' 1859, p. 239. Caspary, 'De Abiet. flor. fem. struct. morphol.' Parlatore, 'Ann. Sc. Nat.,' 1862, vol. xvi, p. 215. Cramer, 'Bildungsabweich.,' p. 4, &c., &c.Gramineæ.—Bauhin, 'Pinax.,' 21. Morison, 'Hist. Plant.,' t. i. Winckler, 'Ephem. Nat. Cur.,' dec. i, ann. 7, 8, p. 151. Irmisch, 'Flora,' 1858, p. 40, &c.See also under Chloranthy, Viviparous plants, &c.

For monstrous plantains, in addition to previous citations, see Camerarius, 'Epist.,' p. 261,P. rosea. Matthioli, 'Krauterb,' 245. Lobel, 'Stirp. Advers. Nov.,' p. 128,P. major paniculata.J. Bauhin, 'Hist. Plant.,' i, p. 503b. Ibid., p. 503,a,c,P. major rosea,bracteata paniculata,prolifera, &c. 'Hort. Eystett.,' pl. æstiv., t. vii, f. 2,P. roseaetP. bracteata. Lobel, 'Stirp. Hist.,' p. 162. Dodonæus, 'Pempt.,' 1–4, cap. xxiii, P. major spica multiplex,i.e.paniculata. Gerard, 'Herbal.' Clusius, 'Plant. Rar. Hist.,' lib. v, p. 109–10,Plantago augustifolia Gareti prolifera. Marchand, 'Adansonia,' iv, p. 156.

Coniferæ.—Richard, 'Mem. Conif.,' tab. xiii, f. 9. A. Braun, 'Das Individ.,' 1853, p. 65. De Cand., 'Organogr.,' tab. xxxvi. Wigand, 'Bot. Untersuch.,' 154. Schlechtendal, 'Bot. Zeit.,' 1859, p. 239. Caspary, 'De Abiet. flor. fem. struct. morphol.' Parlatore, 'Ann. Sc. Nat.,' 1862, vol. xvi, p. 215. Cramer, 'Bildungsabweich.,' p. 4, &c., &c.

Gramineæ.—Bauhin, 'Pinax.,' 21. Morison, 'Hist. Plant.,' t. i. Winckler, 'Ephem. Nat. Cur.,' dec. i, ann. 7, 8, p. 151. Irmisch, 'Flora,' 1858, p. 40, &c.

See also under Chloranthy, Viviparous plants, &c.

Prolification of the flower.—In the preceding sections the formation of adventitious buds of a leafy or floral nature on the inflorescence has been considered. A similar production of buds may take place in the flower itself,either from its centre or from the axil of some of its constituent parts. Prolification of the flower is therefore median or axillary, and the adventitious bud itself may be of a leafy or a floral nature.

Median leafy prolification.—In this malformation the centre of the flower is occupied by a bud or a branch; the growing point or termination of the axis which ordinarily ceases to grow after the formation of the carpels, takes on new growth. This is well shown in the accompanying illustration (fig. 58), representing the thalamus of a strawberry prolonged beyond the fruits into a small leaf-bearing branch.

Fig.58.—Receptacle of strawberry prolonged into a leafy branch. From the 'American Agriculturist.'

Fig.59.—Flower ofVerbascumwith five disunited sepals, five similar green petals, and a prolonged branch in the centre of the flower.

In other cases the carpels are entirely absent and their place is supplied by a leafy shoot as in a species ofVerbascum, which came under my own observation. In this case the petals were virescent, and the stamens and pistils were entirely absent, hence in truth, the so-calledflower more nearly resembled a branch. In a flower of a May Duke cherry, for which I am indebted to Mr. Salter, there was a gradual change from the floral to the foliar condition; thus there were five distinct lanceolate sepals, the arrangement of whose veins betokened that they were leaf-sheaths rather than perfect leaves, ten petals partly foliaceous and sheath-like as to their venation, one of them funnel-shaped, but whether from dilatation or cohesion of the margins could not be determined. The stamens were eight or ten in number, their connectives prolonged into foliaceous or petaloid appendages, so that the filament represented the stalk of the leaf. The pistil was entirely absent and its place was supplied by a branch with numerous perfectly formed stipulate leaves.

Some flowers ofAnagallis arvensisdescribed by Dr. Marchand[119]are so interesting and show so well the gradual stages by which this malformation is arrived at, that it is desirable to cite the summary of Dr. Marchand's researches as given in the 'Gardeners' Chronicle' by Mr. Berkeley, taking that instance first in which the parts of the flower departed least from the normal condition, and then the others in their proper order. In all the parts there was a greater or less tendency to assume a green tint; in some they were entirely green, in others the brighter colours were confined to the more recently developed parts.

"1. In the first case then, the sepals and petals were in their normal position, though rather more dilated than usual; the anthers were fertile, the principal change existing in the ovary, the upper part of which was wanting, so that the ovules were exposed seated on the central placenta.

2. In the next step the calyx, more developed than usual, was separated from the corolla by a long peduncle, and the ovary, which was ovate, contained instead of a placenta a sort of plumule or young shoot.

3. In this case the corolla and calyx were distant from each other; there was no trace of stamens, but the axis was continued from the centre of the corolla, and ended in a leaf-bud.

4. The calyx and corolla nearly as before, but instead of stamens a whorl of little leaves was developed, in the centre of which the axis was continued, bearing at its tip two whorls of leaflets, alternately three and three.

5. In this case two out of the five stamens were normal, the other three changed into leaves, showing clearly the origin of the leaflets, in the last case, which took the place of the stamens.

6. The ovary varied in different flowers. In some the placenta was crowned with ovules; in others the ovules were replaced by a single whorl of leaflets; in others there was every shade of change from ordinary ovules to perfect leaflets; while in others, again, every ovule was converted into a leaf with a long petiole.

7. In these flowers shoots were developed in the axils of the sepals, or on the face of the petals between the point of their insertion and that of the stamens, and, what is most curious, in the interior of the ovaries round the foot of the placenta.

8. Here, again, a very singular condition presented itself: the calyx and corolla separated from each other, the stamens partly developed, the axis continued beyond the corolla, branched and bearing normal leaves so as exactly to resemble an ordinary stem, while in consequence of the calyx and corolla being bent down to the ground, adventitious roots were developed from the axis on the under side above each of them. In another case, where the calyx and corolla were approximated, the ovary was open above, and sent out six shoots from within, perfectly developed, clearly representing the central placenta and five axile buds, and each giving out a number of adventitious roots at its base."

In other genera of the same order (Primulaceæ) anextension of the placenta into a leafy branch has been observed, as inLysimachia, where in one case the prolonged placenta was removed and struck as a cutting.[120]

InEricaceætoo, the axile placenta has been seen ovuliferous at the base and prolonged above into a leafy branch.[121]

Median floral prolification.—This is of more frequent occurrence than the preceding. The prolonged axis is more frequently terminated by a flower-bud than by a leaf-bud, though it must be remarked, that the lengthened and protruded stem frequently bears leaves upon its sides, even if it terminate in a flower, and thus the new growth partakes of a mixed leafy and floral nature. Instances of this kind have long been familiar to observers, and have always excited attention from the singularity of their appearance. In one of the old stained-glass windows, apparently of Dutch manufacture, in the Bodleian Picture Gallery at Oxford, is a representation of aRanunculusaffected with median floral prolification.[122]In pinks the affection is not unfrequently met with. Fig. 60 shows an instance of the kind copied from Schotterbec.

A singular instance of prolification in the central flower of one of the verticillasters ofPhlomis fruticosafell under my own notice; it was a case wherein the calyx was torn on one side, and one of its lobes had become petaloid. Between the calyx and the corolla were three or four spathulate, hairy, bract-like organs; the corolla and stamens were unchanged; but in place of the usual four-lobed ovary there was a single carpel with a basilar style, terminated by a forked stigma. Occupying the place of the other lobes of the pistil was an oblong woolly flower-bud, consisting of calyx, corolla, and stamens, but with no trace of pistil. Ihave been unable to find recorded any instance of malformation among Labiates or Borages at all similar to this. It differed from most other examples of prolification in that the axis was not prolonged, the adventitious bud occupying precisely the position of the three lobes of the ovary that were absent. The sole remaining carpel had a style and a stigma as perfect in appearance as though the pistil had been complete.

Fig.60.—Flower ofDianthusaffected with median floral prolification.

In a flower ofConostephium(Epacridaceæ) forwarded to me by Mr. Bentham, there was a similar adventitious bud placed by the side of the pistil, but as the latter contained the usual number of cells it is probable that the supernumerary bud in this case originated rather from the side than the end of the axis.

Certain families of plants present this deviation from their ordinary structure with greater frequency than others: the following orders seem to be the most frequently affected by it:Ranunculaceæ,Caryophyllaceæ,Rosaceæ; while it is commonly met with inScrophulariaceæ,PrimulaceæandUmbelliferæ. Of genera which seem peculiarly liable to it may be mentioned the following:Anemone,Ranunculus,Cheiranthus,Dianthus,Dictamnus,Daucus,Rosa,Geum,Pyrus,Trifolium,Antirrhinum,Digitalis,Primula.

A reference to the subjoined list of genera affected by this malformation, and the knowledge of its comparatively greater frequency in some than in others of them, will show that it is more often met with in plants having an indefinite form of inflorescence than in those having a definite one. The change may affect some only, or the whole of the flowers constituting an inflorescence; and though it is by no means a constant occurrence, it very frequently happens that the central or terminal flower in a definite inflorescence is alone affected, the others remaining in their ordinary condition, as in pinks (Dianthus); and in the indefinite forms of inflorescence, it is equally common that the uppermost flower or flowers are the most liable to be thus affected.

In those plants which present this deviation from the ordinary condition with the greatest frequency, it often happens that the axis is normally more or less prolonged, either between the various whorls of the flower, as in the case of the gynophore, &c., or into the cavity of the carpels, as in the instances of free central placentation. To bear out this assertion, the following instances taken from those genera having definite inflorescence, and which are very commonly affected with prolification, may be cited; thus, inAnemoneandRanunculusthe thalamus is prolonged to bear the numerous carpels; inDianthusthere is a marked internode separating the carpels from the other parts of the flower; inPrimulaceæcentral prolification is very common, and this is one of the orders where the placenta seems from the researches of Duchartre and others, to be truly a production of the axis within the carpels;[123]inThesiumalso, another genus withfree central placenta, this malformation has been found.

So also among plants with indefinite inflorescence, prolification seems very frequently to affect those wherein the axis is normally prolonged; thus it is common inDictamnus, which plant has an internode supporting the pistil; it is frequent amongUmbelliferæ, where the carpophore may be truly considered an axile production; it is common amongRosaceæandRanunculaceæ, in many of which the axis or thalamus is well-marked, and it is by no means infrequent in the flowers of the Orange, where the floral internodes are also slightly elongated; on the other hand, there is no case on record inMagnoliaceæ, and some other orders where the floral part of the axis is at some point or other elongated; still, on the whole, there can be but little doubt that there is a real relation between prolification and the normal extension of the floral internodes.

Under these circumstances, those instances wherein the parts of the flower become separated one from the other by the elongation of the internodes (apostatis), constitute a lesser degree of the same change, which operates most completely in the formation of a new bud at the extremity of the prolonged axis. Some specimens ofGeum rivale(a plant very liable to become prolified) in my possession show this very clearly. In the wild plant the thalamus is elevated on a short stalk; in the abnormal ones the thalamus is simply upon a longer stalk than usual, or in a more advanced stage of the deviation the lengthened thalamus takes the form of a branch provided with leaves and terminated by a flower; it is noticeable, also, in these specimens, that the sepals of the lower flower have assumed entirely the dimensions and appearance of leaves.

Median prolification has occasionally been recorded in flowers that have, in their ordinary condition, but one carpel, as inLeguminosæand inSantalaceæ. InLeguminosæ, as also inAmygdalus, it would seem as ifthe adventitious bud were strictly a lateral and axillary production, and moreover that the carpel itself is not strictly terminal but lateral in position, though apparently terminal from the abortion of other carpels. In the only recorded instance that I am aware of, of this malformation affecting the genusThesium, the pistil was altogether absent, and occupying its place was the new bud or branch.[124]

Fig.61.—Daucus Carota, showing leafly carpels, prolification, &c.

As the carpels are not unfrequently absent in cases of median prolification, it has been thought that the pistil in such cases was metamorphosed into a stem bearing leaves or flowers. Setting aside the physiological difficulties in the way of accepting such an opinion, an examination of any number of cases is sufficient to refute it; for, as Moquin well remarks, the carpels may frequently be found either in an unaltered condition or more or less modified.

If the pistil be normally syncarpous, its constituent carpels, if present at all in the prolified flower, become disjoined one from the other to allow of the passage between them of the prolonged axis; thus in some malformed flowers ofDaucus Carotagathered in Switzerland (fig. 61), not only was the calyx partially detached from the pistil, but the carpels themselves were leaf-like, disjoined, and unprovided with ovules; between them rose a central prolongation of the axis, which almost immediately divided into two branches, each terminated by a small umbel of perfect flowers, surrounded by minute bracts.[125]

Not only are the carpels thus frequently separated one from the other by the prolonged axis, but they undergo commonly a still further change in becoming more or less completely foliaceous, as in theDaucusjust mentioned, where the carpels were prolonged into two lance-shaped leaves, whose margins in some cases were slightly incurved at the apex, forcibly calling to mind the long "beaks" that some Umbelliferous genera have terminating their fruits—for instance,Scandix. Dr. Norman, in the fourth series of the 'Annales des Sciences,' vol. ix, has described a prolification of the flower ofAnchusa ochroleuca, in which the pistil consisted of two leaves, situated antero-posteriorly on a long internode, with a small terminal flower-bud between them; and numerous similar instances might be cited.

In this place may also be noticed those instances wherein the placenta elongates so much that the pericarp becomes ruptured to allow of the protrusion of the placenta, although this prolongation is not attended by the formation of new buds. Cases of this kind occurring inMelastomaandSolanumhave been put on record by M. Alph. de Candolle.[126]This is a change analogous with that which occurs in some species ofLeonticeorCaulophyllum, as commented on by Robert Brown. See 'Miscellaneous Botanical Works' of this author, Ray Society, vol. i, p. 359.

If the pistil be apocarpous, and the carpels arranged spirally on an elevated thalamus, it then frequently happens that the carpels, especially the upper ones,become carried up with the prolonged axis, more widely separated one from the other than below, and particularly liable to undergo various petalloid or foliaceous changes as in proliferousRoses,Potentilla, &c.

Fig. 62.—Median floral prolification, &c., in flower ofDelphinium.

Fig. 62, copied from Cramer, shows an instance of this kind inDelphinium elatum, where not only is the thalamus prolonged, and the carpels separated, but from the axils of some of the latter which haveassumed from the disunion of their margins somewhat of the appearance of leaves, other flowering branches proceed—axillary prolification. If, on the other hand, the carpels be few in number, and placed in a verticillate manner, the axis then generally passes upwards without any change in the form or position of the carpels being apparent, as in a proliferous columbine, figured in the 'Linnean Transactions,' vol. xxiii, tab. 34, fig. 5.

When a flower with the ovary naturally inferior or adherent to the calyx becomes prolified, a change in the relative position of the calyx and ovary almost necessarily takes place, the latter becoming superior or detached from the calyx; this has been already alluded to inUmbelliferæ. In a species ofCampanulaexamined by me, the calyx was free, the corolla double, the stamens with petaloid filaments, and in the place of the pistil there was a bud consisting of several series of green bracts, arranged in threes, and enclosing quite in the centre three carpellary leaves detached from one another and the other parts of the flower, and open along their margins, where the ovules were placed. In other similar instances in the same species ofCampanula, the styles were present, forming below an imperfect tube which surrounded the adventitious bud; in another, contrary to what occurs usually in such cases, the ovary was present in its usual position, but surmounted by a bud of leafy scales, enclosed within the base of a tube formed by the union of the styles. A similar relative change in the position of the calyx and the ovary takes place when theCompositæare affected with central prolification, or even in that lesser degree of change which merely consists in the separation and disunion of the parts of the flower, but which in these flowers appear to be, as it were, the first stage towards prolification. I owe to the kindness of Professor Oliver a sketch of a species ofRudbeckia? showing this detachment of the calyx from the ovary. In a monstrousFuchsiathat I have had the opportunity of recently examining, the calyx wassimilarly detached from the ovary simultaneously with the extension of the axis. Here the petals were increased in number and variously modified, the stamens also; while in the centre and at the top of the flower, conjoined at the base with some imperfect stamens, was a carpel open along its ovuliferous margins. Such instances as these seem to be the first stages of a change which, carried out more perfectly, would result in the formation of a new bud on the extremity of the prolonged axis.

InOrchidaceæ, among which family I have now met with several instances of prolification, the ovary seems usually to be absent. Fig. 63 shows a prolified flower ofOrchis pyramidalisin which the perianth was nearly regular, the central portions of the flower absent, and their place supplied by a new miniature raceme. This specimen was forwarded to me by Dr. Moore, of Glasnevin.

Fig.63.—Median prolification inOrchis pyramidalis, the outer segments of the perianth regular and reflexed.

As might be expected, it very rarely happens that median prolification occurs without some other deviation in one or more parts of the flower being simultaneously manifested. Some of these changes have been already mentioned, but others are commonly met with, as, for instance, the multiplication or doubling, as it is termed, of the petals; others, though less frequent, are of moreinterest. Fusion of two or more flowers in association with prolification is especially common in cultivated specimens ofDigitalis purpurea; the uppermost flowers of the raceme become fused together so as to form one large, regular, erect, cup-shaped corolla, to the tube of which the stamens are attached, in greater number than ordinary, and all of equal length; the bracts and sepals are confusedly arranged on the exterior of the flower; while in the centre, in the place usually occupied by the pistil, there rises a conical prolongation of the axis, bearing at its outer or lower portion a number of open carpels, provided, it may be, with styles and ovules; these enclose an inner series of scale-like bracts, from whose axils proceed more or less perfect florets; so that in the most highly developed stage a perfect raceme of flowers may be seen to spring from the centre of a cup-shaped regular flower, whose lobes show its compound character. All intermediate stages of this malformation may be found from cases where there is a simple fusion of two flowers with a second verticil of carpels within the outer, up to such cases as those which have been just mentioned. It is worthy of special remark, that in all these cases the flowers at the uppermost part of the raceme are alone affected, and that, in addition to the prolification, there is fusion of two or more flowers, and regularity in the form of the compound corolla and stamens.

The calyx of a prolified flower is either unchanged, or it is modified in harmony with the changes in the central part of the flower. If the ovary be normally superior or free from the calyx, then the latter is comparatively rarely altered; for instance, in proliferous pinks (Dianthus) the calyx is seldom affected, except, indeed, in those instances where the floral axis is prolonged, and produces from its side a successive series of sepals, as in what is called the wheat-ear carnation; but though these instances may be, as I believe, an imperfect degree of prolification, they do not affect the general truth of the above opinion, that the calyx, if it be freefrom the ovary, is but rarely changed in a prolified flower; but that this is not a universal rule is shown by proliferous flowers ofGeum rivale, where the sepals are usually large and leaf-like, as they likewise are frequently in proliferous roses and pears.

Fig.64.—Proliferous rose. Hip absent, sepals leafy, stamens wanting, axis prolonged bearing supplementary flower, &c. (Bell Salter).

Proliferous roses have a special interest, inasmuch as they show very conclusively that the so-called calyx-tube of these plants is merely a concave and inverted thalamus, which, in prolified specimens, becomes elongated(fig. 64) after the fashion ofGeum rivale, &c.[127]Occasionally from the middle of the outer surface of the urn-shaped thalamus proceeds a perfect leaf, which could hardly be produced from the united sepals or calyx-tube; a similar occurrence in a pear is figured in Keith's 'Physiological Botany,' plate ix, fig. 12.

The change which the calyx undergoes when flowers with an habitually adherent ovary become prolified, and wherein the calyx is disjoined from the ovary, has been before mentioned, but it may also be stated that, under such circumstances, the constituent sepals are frequently separated one from the other, and not rarely assume more or less of the appearance of leaves, as in proliferous flowers ofUmbelliferæ,Campanulaceæ,Compositæ, &c.

As to the corolla, it was long since noticed that prolification was especially liable to occur in double flowers; indeed, Dr. Hill, who published a treatise on this subject, setting forth the method of artificially producing prolified flowers, deemed the doubling to be an almost necessary precursor of prolification;[128]but, though frequently so, it is not invariably the case that the flower so affected is double—e.g.Geum. If double, the doubling may arise from actual multiplication of the petals, or from the substitution of petals for stamens and pistils, according to the particular plant affected. Occasionally in prolified flowers the parts of the corolla, like those of the calyx, become foliaceous, and in the case of proliferous pears fleshy and succulent. There is in cultivation a kind ofCheiranthus? in which there is a constant repetition of the calyx and corolla, conjoined with an entire absence of the stamens and pistils; a short internode separates each flower from the one above it, and thus frequentlyten or a dozen of these imperfect flowers may be seen on the end of a flower-stalk, giving an appearance as if they were strung like beads, at regular intervals, on a common stalk. I have seen a similar instance in a less degree in a species ofHelianthemum.

The stamens are subject to various changes in prolified flowers; they assume, for instance, a leaf-like or petal-like condition, or take on them more or less of a carpellary form, or they may be entirely absent; but none of these changes seem to be at all necessarily connected with the proliferous state of the flower. Of more interest is the alteration in the position of these organs which sometimes necessarily accrues from the elongation of the axis and the disjunction of the calyx; thus, in proliferous roses the stamens become strictly hypogynous, instead of remaining perigynous. InUmbelliferæthe epigynous condition is changed for the perigynous, &c.

The condition of the pistillary organs in prolified flowers has already been alluded to. Hitherto those instances have been considered in which either the carpels were absent, or the new bud proceeded from between the carpels. There is also an interesting class of cases where the prolification is strictly intra-carpellary; the axis is so slightly prolonged that it does not protrude beyond the carpels, does not separate them in any way, but is wholly enclosed within their cavity. Doubtless, in many cases, this is merely a less perfect development of that change in which the axis protrudes beyond the carpels. This intra-carpellary prolification occurs most frequently in plants having a free central placenta, though it is not confined to them, as it is recorded amongBoragineæ. A remarkable instance of this is described by Mr. H. C. Watson in the first volume of Henfrey's 'Botanical Gazette,' p. 88. In this specimen a raceme of small flowers was included within the enlarged pericarp of a species ofAnchusa. But the most curious instances ofthis form of prolification are, no doubt, those which are met with amongPrimulaceæand other orders with free central placentation.

Duchartre, in his memoir on the organogeny of plants with a free central placenta, in the 'Ann. des Sc. Nat.,' 3 sér., 1844, p. 290, among other similar instances, mentions two flowers ofCortusa Matthioli, wherein the placenta was ovuliferous at the base; but the upper portion, instead of simply elongating itself into a sterile cone, had produced a little flower with its parts slightly different from those of the normal flowers. M. Alph. de Candolle has likewise described somewhat similar deviations, and one in particular inPrimula Auricula, where the elongated placenta gave off long and dilated funiculi bearing ovules, while other funiculi were destitute of these bodies, but were much dilated and foliaceous in appearance.[129]In some flowers ofRhododendronI have observed a similar condition of the ovules, which, moreover, in the primary flowers, were attached to the walls of the carpels—parietal placentation.

In speaking of these as cases of intra-carpellary prolification, it is, of course, impossible to overlook the fact that they differ in degree only from those cases where the lengthened axis projects beyond the cavity of the carpels; nevertheless they seem to demand special notice, because in these particular plants the placenta or its prolongation appears never to protrude beyond the carpels, or at least very rarely. There are, however, numerous instances of such an extension of the placenta and of prolification occurring amongPrimulaceæin conjunction with the more or less complete arrest of growth of the carpels.[130]An instance of this kind has come under my own notice in a monstrosity of the chinese primrose, in which the carpels were reduced to a hardly discernible rimsurrounding an umbel of five rays, each terminated by a small normally constituted flower-bud.

The ovules of a prolified flower are either unaffected, or they occur in a rudimentary form, or, lastly, they may be present in the guise of small leaves.

Under the term prolification of the fruit two or three distinct kinds of malformation appear to have been included. The term seems usually to be applied to those cases where from the centre of one fruit a branch bearing leaves, flowers, or another fruit, is seen to project, as happens occasionally in pears. Now, in many instances, not only the fruit, is repeated, but also the outer portions of the flower, which wither and fall away as the adventitious fruit ripens; so that at length the phenomenon of one fruit projecting from another is produced. It is obvious that this form of prolification in no wise differs from ordinary central prolification. Sometimes some of the whorls of the adventitious flower are suppressed; thus, M. Duchartre describes some orange blossoms as presenting alternating series of stamens and pistils one above another, while the calyces and corollas belonging to each series of stamens and pistils were entirely suppressed.[131]In other cases, doubtless, the carpellary whorl is alone repeated, the other whorls of the adventitious flower being completely absent.

Another condition, apparently sometimes mistaken for prolification of the fruit, is that in which the carpellary whorl becomes multiplied; so that there is a second or even a third series within the outer whorl of carpels. If the axis be at all prolonged, then these whorls are separated one from the other, and produce in this way an appearance of prolification. This happens frequently in oranges, as in the variety called Mellarose.[132]

Moquin has given an explanation of the St. Valery Apples, wherein the petals are sepaloid, the stamens absent, and where there is a double row of carpels, by supposing these peculiarities to be due to "a prolification combined with penetration and fusion of two or more flowers," but it is surely more reasonable to conceive a second row of carpels placed above the first by the prolongation of the central part of the axis. Supposing this view to be correct, the inner calyx-like whorl might be considered either as a repetition of the calycine whorl, or it might be inferred that the corolla was present in the guise of a second calyx.

Moquin-Tandon suggests another explanation—namely, that though the stamens are absent in these curious flowers, at least in their ordinary shape, they are represented by the lower row of carpels, which become, in process of development, fused with the upper or true carpels. If this were so, surely some intermediate conditions between stamen and carpel would occasionally be present; but such does not appear to be the case.[133]

In some of the instances of so-called proliferous pears the carpels would seem to be entirely absent, and the dilated portion of the axis to be alone repeated. Thus, the axis dilates to form the lower fruit without any true carpels being produced, but at its summit a whorl of leaves (sepals) is formed; above these another swelling of the axis takes place also without the formation of carpels, and this, it may be, is terminated in its turn by a branch producing leaves. In these cases there is no true prolification, but simply an extension of the axis. That the outer portion (so-called calyx-tube) of these fruits is really an axile product there can now be little doubt; and, as if to show their axile nature, they occasionally produce leaves from their sides, asbefore mentioned. Moquin, in the tenth volume of the 'Bulletin of the Botanical Society of France,' p. 73, says that when the case is one of prolification the lower fruit is larger and is formed of a fleshy mass; moreover, the line of demarcation between the fruits is more distinct, and there are traces of the seed-bearing cavity in the interior, and of calycine lobes at the top. On the other hand, if the case be one of hypertrophy merely, the lowermost fruit is the smallest, and there is no trace of seed-bearing cavity nor of sepals. See also under Hypertrophy.

Some other malformations usually referred to prolification of the fruit seem due to branching of the inflorescence, as inPlantago, wheat, maize; or to a simple extension of the axis beyond its ordinary limit, as in some cones of firs, &c. It is obvious that the true fruits in these cases are in no wise affected.

From these considerations it would appear better to abandon the use of the expression prolification of the fruit, as unnecessary where it is really applicable, and as delusive in the numerous other cases where it is employed.

Median prolification of one or other kind has been met with in the following genera:

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