Chapter 13

See Moquin-Tandon, 'El. Terat. Veg.,' p. 203. Engelmann, 'De Anthol.,' § 38et seq.; tab. ii, figs. 8–14,Gilia; tab. v, 23–26,Senecio; tab. v, f. 1–13,Torilis; tab. iv, f. 3,Erysimum. 'Bull. Soc. Bot. Fr.,' vol. ii, 1855, p. 479,Primula sinensis. Giraud, 'Edinb. Phil. Magazine,' 1839,Antirrhinum. Jaeger, 'Act. Acad. Cæs. Nat. Cur.,' vol. xiii, 2, p. 1, tab. xli,Tropæolum. Bischoff, 'Lehrbuch,' 11, 2, p. 27,note,Tropæolum. Fresenius, 'Mus. Senkenb.,' ii, 35, tab. 4, fig. 5,Actæa. See also succeeding paragraphs and sections in Chloranthy, Virescence, &c.

Phyllody of the stamenshappens less frequently than the corresponding condition in the neighbouring organs. The structure of the anther is so much removed from that of the leaf, that the change of the stamen from its ordinary condition to that of a leaf must be regarded as indicating a greater degree of perverted development than that which occurs in those cases where less highly differentiated organs, such as the sepals, petals, and pistils, are thus altered.[260]

In all cases it is desirable to ascertain, if possible, what parts of the stamen are thus transformed. In some Petunias the filaments are unchanged, but in place of the anther is a small lamina, representing precisely the blade of an ordinary leaf. Sometimes the connective only is replaced by a leaf. One of the most interesting cases of this kind that has fallen under the writer's observation was inEuphorbia geniculata, in which, in addition to other changes mentioned under prolification of the inflorescence, some of the stamens were partly frondescent,half the anther being perfect, the other half leaf-like. Another filament bore just above the usual joint three leaflets, two lateral ones, somewhat conduplicate, and a third central one, half anther, half leaflet.

Fig.134.—Flower of aPetunia, opened to show the stamens partially replaced by stalked leaves.

In the case of frondescent flowers ofTropæolum majusthe stamens are usually absent or atrophied, but in other instances the filament is present as usual, representing the stalk of the leaf, and surmounted by a small lamina, but this latter, in place of being nearly flat, is pinched up in the centre from back to front, and surmounted by a two-lobed anther, so that the general appearance of the whole structure is that of a central anther, supported at the base on each side by two concave leaf-lobes, or it might be compared with a three-lobed leaf, the terminal lobe represented by the anther.

InJatropha Pohliana, Müll. (Adenorophium luxurians, Pohl.), a singular condition has been observed by M. Müller (Argov.). In this flower the anther, in placeof being represented by the flat blade of a single leaf, had the appearance as if two such blades were present and coherent one with the other by their midribs, along their upper or inner surfaces, which were directed towards the centre of the flower (fig. 136), thus resembling the cases of adhesion of leaves by their surfaces already referred to (p. 33). In other cases, in the same plant, the anther appeared as if formed by two collateral leaves, the faces looking towards the circumference of the flower, and their margins so folded together as to represent an open anther lobe (fig. 135). These cases are apparently due, not to the formation and adhesion of two leaves, but rather to the exuberant development of one leaf into two blades.[261]The bearings of these and other similar malformations on the morphology of the anther are alluded to under the head of petalody of the anther.

Fig.135.—Phylloid anther ofJatropha, after Müller (Arg.).

Fig.136.—Leaf-like anther ofJatropha Pohliana, after Müller.

Phyllody of the stamens has been most often observed in the following plants:

Anemone nemorosa.coronaria.Delphinium crassicaule.Nymphæa dentata.Tropæolum majus!Dictamnus albus.*Trifolium repens!Torilis anthriscus.Heracleum Sphondylium.Daucus CarotaEpilobium hirsutum!*Rosa, var. cult.!Lonicera Periclymenum.Anagallis arvensis.Primula sinensis!Petunia, var. cult.Jatropha Pohliana.Euphorbia goniculata.

In addition to the foregoing there are very numerous instances of similar substitution in chloranthic flowers. In the above list only those cases are given wherein the leafy change is confined to the stamens, or, at least, to a few only of the other parts of the flower.

Phyllody of the pistils.[262]—This is of more common occurrence than is the corresponding change in the case of the stamens. It is of interest, as it sometimes serves to illustrate the morphological nature of the pistil. Of this the double-flowering cherry is a well-known illustration, the pistil being here represented by two small foliar laminæ, whose midribs are prolonged with a short style, terminated by an imperfect stigma. It is usually the basal portion of the pistil, the ovary, which is thus specially affected, the margins being also often disunited so as to expose the ovules. These latter organs may be absent or they may themselves be the subjects of foliaceous development. Moquin[263]relates having found in the neighbourhood of Montpellier a flower of a tulip the ovary of which was represented by true leaves, which bore on their margins the ovules, and thus presented a striking analogy with the carpels of those Sterculias, likeS. platanifolia, which are foliaceous in texture and open very early in the course of their development. A similar occurrencehas also been frequently noticed in the Columbine and also inCruciferæandUmbelliferæ. M. Germain de St. Pierre mentions an instance wherein the carpels ofSalix Babylonicawere converted into two leaves, provided with stipules. All the flowers of the catkinswere similarly changed, so that it became permanent, and resembled a branch.

Fig.137.—Rose, in which the axial portion of the flower was elongated and the carpels were more or less replaced by leaves.

Substitutions of this kind form the green "eyes" or centres of certain varieties ofRanunculusandAnemone.

In proliferous roses, or in cases where the central axis of the flower is prolonged, it frequently happens that the pistils are more or less replaced by leaves. Fig. 137, from a specimen of Dr. Bell Salter's, given in the 'Gardeners' Chronicle,' shows the passage, from below upwards, of the ordinary carpels to perfect leaves; the so-called calyx-tube being completely deficient and the ovaries entirely superior. Like most similar specimens, this one bears out the notion that what is called the calyx-tube in roses is really an expansion and dilatation of the top of the flower-stalk.

Fig.138.—Cucumber with leaf attached.

Fig. 138, for which I am indebted to Mr. S. J. Salter, represents a very singular conformation in the cucumber, described by that gentleman in 'Henfrey's Botanical Gazette,' i, p. 208, and considered by him to be due to the foliaceous condition of one of the three carpels of which the fruit is composed. The portion near the peduncle was binary, while the distal extremity of the fruit was ternary. The main difficulties attending the acceptance of this explanation reside in the peculiar reversed position of the leaf, and in the fact that the fruit of theCucurbitaceæis probably of axial nature, the dilated and succulent end of the peduncle adhering to and usually concealing the carpels; in some cases, however, these latter project beyond the axial portion, leaving no doubt as to the true nature of the structure in these particular instances.

Admitting the axial nature of the fruit, it might be supposed that in Mr. Salter's cucumber an adventitious leaf had been given off from the axis, but even on that supposition the reversed position offers a difficulty, and there still remains to be explained the fact that the proximal part of the fruit was binary in its constitution, the distal end ternary.

M. Norman[264]mentions a case wherein the carpels ofAnchusa ochroleucawere replaced by two leaves; from this he draws the inference that the pistil of borages and labiates is really composed of two leaves, placed fore and aft, the margins of the leaves being congenitally fused. This tallies well with the account given of the development of these plants by Payer, Germain de St. Pierre, and others.

In an Indian species ofTriumfetta, not only were the petals virescent, but the ovary also was much enlarged, and in some flowers it was divided half way down into five lanceolate leaves (fig. 139), the sepals and stamens being in their normal condition.

In the preceding instances the foliaceous condition has pervaded the entire pistil, or at any rate the basal portion or ovary, and it may be noticed that the ovary is thus shown to consist in some cases of the sheath of the leaf, as inAquilegia; in other cases of the blade, as inCerasus,Daucus, &c.

Fig.139.—Flower ofTriumfetta, sp., carpels represented by five leaves.

There are cases, however, in which a part only of the pistillary structure thus becomes foliaceous. Linnæus, 'Prolepsis,' § 9, mentions some flowers ofCarduus heterophyllusandC. tataricusin which the style had grown into two green leaflets, and in which the calyx and corolla were also leaf-like. A very singular instance is recorded by Baillon,[265]wherein the pistil ofTrifolium repensconsisted of three carpels, either separate, or combined so as to form a one-celled ovary with three parietal, pluri-ovulate placentæ; the ovary in these flowers was formed of the basal vaginiform part of the leaf; the three styles were formed by the petioles, while the stigmas were represented by trifoliolate leaves. The back of the leaf in these cases is usually directed away from the centre of theflower. When this change occurs it is commonly attended by an increased number of parts, as in the trefoil just mentioned, or in the double cherry, where usually two foliaceous carpels may be met with, and sometimes more.

The change is also of interest when it affects such orders as theUmbelliferæ, which have their ovaries inferior under ordinary circumstances; but when these organs assume a leafy condition they become superior also,i.e.they are detached from the calyx.

As regards the position of the ovules in these foliaceous pistils, they may be placed, as inAquilegia,Delphinium, &c., on the edges of the carpel or on the surface, as in some flowers ofRanunculus repensandR. Ficaria. A similar position of the ovules is recorded in the case of the vine (Vitis), where the pistil consisted of leaves bearing the ovules on their inner surface.[266]The supposed causes of this and other similar malformations are alluded to under the head of chloranthy, but it may be here remarked that semi-double flowers, fertilised by the pollen of similar flowers, are said to produce flowers with a centre of small green leaves, this central tuft resulting from the expansion and frondescence of the pistils.

As this condition rarely occurs without corresponding changes in other parts of the flower, further remarks on this subject will be found in the chapter relating to Chloranthy.

Phyllody of the pistil has been most frequently recorded in the following plants:

Pæonia officinalis.Ranunculus repens!*Aquilegia vulgaris!Delphinium elatum.crassicaule.Ajacis.amænum.Nymphæa dentata.Sinapis arvensis!Diplotaxis tenuifolia.*Brassica oleracea!*Sisymbrium officinale!Dianthus. spReseda Phyteuma.Triumfetta, sp.!Lychnis dioica.Cerastium, sp.!*Dictamnus Fraxinella!Cerasus avium.vulgaris!*Rosa, var. cult.!*Daucus Carota!Heracleum, sp.Epilobium hirsutum!Lathyrus latifolius.*Trifolium repens!hybridum.Melilotus, sp.Medicago, sp.Lonicera Periclymenum.Carduus heterophyllus.tataricus.Scrophularia aquatica.Symphytum officinale.Anchusa ochroleuca.paniculata.*Primula sinensis!Salix babylonica.Hyacinthus, sp.Tulipa, sp.

Some of the above are probably cases of mere virescence rather than of phyllody. For further illustrations, references to authorities, &c., see under Chloranthy, Virescence, Prolification, &c.

Phyllody of the ovules.—Pending the settlement of the existing differences of opinion with reference to the morphological nature of the ovule and its component parts, much interest attaches to the malformations to which they are occasionally subject. Considered purely in a teratological point of view, it seems clear that the ovular coats are usually, if not always, of foliar nature, while the central nucleus is an axial organ; but if this be so there still remains the question whether the leafy coats of the ovule are processes of the carpel itself, or distinct independent formations, like the scales of a leaf-bud; as to this latter point, the evidence is at present very conflicting. Prof. Al. Braun, who has devoted much attention to the subject, describes and figures ovules ofNigellaandAdonis, wherein the outer coat of the ovule was converted into a leafy, lobed mass, like the ordinary leaves, and these he considers to be a portion, not of the carpel, but of the ovular bud; he, however, hesitates to pronounce an opinion on the nature of the pedicel of the ovule. InPrimulaceæ, wherein ovular changes are very common, the leafy coat of the ovule would seem, from the nature of the placenta, to be independent of the carpel. Morren, who studied the changes in theovules ofPrimula sinensis, applied the term lepyrophylly (λεπυρον, a scale) to the foliaceous condition of the testa in this plant. Unger[267]describes a series of malformations inPrimula sinensis, consisting chiefly of reversions of the part of the flower to leaves. The carpels were entirely absent in this case, and the place of the free central placenta was occupied by a circle of leaves, sometimes bearing imperfect ovules on their edges. An instance of a similar kind has been described by A. de Candolle.[268]

In these flowers the placenta seemed to be composed of several funiculi soldered together, and bearing imperfect ovules. In other cases no traces of ovules are visible, but the funiculi are in a foliaceous condition. Moquin also alludes to a case of the same nature inCortusa Mathioli, in which the funiculi bore little rounded leaves. Brongniart has described some malformations ofPrimula sinensisin which the ovules were transformed wholly or partially into small leaves with three to five lobes.[269]Dr. Marchand[270]mentions similar changes inAnagallis arvensisandLonicera Periclymenum.

Cramer[271]figures ovules ofPrimula sinensisin the form of stalked leaves, often becoming infolded at the margins, and giving origin to a small nucleus on their inner surface.

M. Tassi[272]records an instance inSymphytum officinalewherein the ovules were replaced by two small linear leaves arising entirely from the axis, and not from the carpels.

In most of the foregoing illustrations the foliar portion of the ovule must have been independent of the carpel; this independence is less manifest, though probably asreal in the cases now to be mentioned. InSinapisand inBrassica oleraceafoliaceous ovules may occasionally be seen, attached to the placenta by long stalks. No trace of the nucleus is visible in these specimens.

Fig.140.—Sinapis, replum and ovules; the dotted line shows the position of the carpels.

Griffith, in alluding to a similar case inSinapis,[273]describes the ovules as foliaceous, and having their backs turned away from the axis, the raphe being next to the axis and representing the midrib the funicle corresponding to the petiole. The outer tegument of the ovule, according to Griffith, is a leaf united along its margins, but always more or less open at its apex. No inversion can, therefore, really take place in anatropous ovules, but the blade of the leaf is bent back on the funicle, with which its margins also cohere.

Caspary, in an elaborate paper on phyllomorphy occurring inTrifolium repens, figures foliaceous ovules springing from the edge of an open, leafy carpel. The nucleus of the ovule, in these cases, appears to originate as a little bud from the surface of the leafy ovule (figs. 141, 142).

Fig.141.—Leafy ovules, &c.,Trifolium repens.

In a species ofTriumfetta(see p. 260), of which I examined dried specimens, the ovary was open and partly foliaceous; it bore on its infolded margins ten erect leaflets, representing so many ovules; each leaflet was conduplicate, the back being turned towards the placenta.

Fig.142.—Leafy ovules ofTrifolium repens, showing formation of nucleus, &c. After Caspary.

On the other hand, there are cases in which the leafy coat of the ovule, in place of being a distinct organ, seems to originate from the margin of the carpellary leaf itself—to be, as it were, a lobule or small process of the carpel, and not an absolutely new growth. Thus, Planchon[274], from an examination of some monstrous flowers ofDrosera intermedia, was led to the inference that the ovules are analogous to hairs on the margins of the leaves. This acute botanist was enabled to trace all the gradations between the simplecup formed by the confluence of four glanduliferous hairs and the concave leaf and the perfect ovule.

Brongniart[275]records ovules ofDelphinium elatumexisting in the form of marginal lobes of the carpellary leaf itself; so that each ovule corresponds to a lobe or large tooth of this leaf, the funiculus, as well as the raphe, being formed by the median nerve of the lateral lobe. M. Clos[276]mentions a similar instance inAquilegia Skinneri; and another is figured in Lindley's 'Elements of Botany,' p. 88, f. 180.

Fig.143.—Portion of an open foliaceous carpel ofDelphinium, with ovules on the lobules.

Cramer[277], from an examination of several ovular malformations, as well as from the investigation of the mode of evolution of the ovules, is led to a similar conclusion with reference to the production of ovulesfrom the modified lobes of the carpellary leaf. Figs. 143–145, copied from Cramer, show how the nucleus of the ovule is formed as a new growth from the surface of the lobes of the leaf inDelphinium elatum.

Fig.144.—Section through marginal lobe of carpel (Delphinium), showing the nucleus (n).

Fig.145.—Section through marginal lobe of carpel, showing nucleus and tegument (Delphinium).

Fig.146.—1. Placenta ofDianthus, bearing ovules and carpels. 2. One of the ovaries separated.

Fig.147.—Ovules ofDianthuspassing into carpels.

One of the most singular instances of ovular malformation in record is that cited by the Rev. M. J. Berkeley, in the 'Gardener's Chronicle,' September 28th, 1850, p. 612. The plant was a carnation, and its placenta bore, not only ovules, but also carpels (fig. 146), the latter originating in a perverted developmentof the former, so that many intermediate stages could be traced between the ordinary ovule and the ovary (fig. 147, 1,a, 2,b). Some of these carpels, thus derived from the ovules, themselves bore secondary ovules on a marginal placenta, as shown in the sections atc,d,e. Could such a change occur in the animal kingdom, there would be the unfertilised ovumconverted into an ovary, and this again bearing Graafian vesicles! In Mr. Berkeley's carnation the change was not so great, seeing that the nucleus of the ovule was not developed, and sufficient evidence has been above given as to the foliar nature of the primine, while for a leaf to be folded up so as to form a carpel is an ordinary occurrence.

It is worthy of remark that in these foliaceous ovules there is never more than one coat, the secondine and other integuments do not make their appearance in these cases, and that very generally the change in question accompanies a similar foliaceous condition in the carpel, the margins of which are more or less disunited.

Prof. A. Braun remarks that up to this date no such change has been observed in the ovules of Monocotyledons.

Changes in the nucleus of the ovule.—The preceding remarks have had reference especially to the ovular coats, but it is desirable also to allude to certain points connected with the nucleus. Very frequently, when the coat of the ovule is phylloid, as before described, the nucleus is altogether wanting, though sometimes it is present as a small cellular papilla; very rarely is it to be found in its perfect state. Occasionally the nucleus is present in the guise of a small elongated branch. Wigand cites ovular buds in every stage of progress into a branch, sometimes even bearing indications of anthers. Wydler has observed a similar occurrence in ovules ofAlliaria officinalis, and Schimper has described and figured specimens ofNigella damascenain which the outer coats of the ovule were but little changed, while the nucleus was replaced by a leafy shoot. On one of the leaves of this latter was found an imperfect ovule—an ovule on an ovule!

Fig. 148 shows a floret of a species ofGaillardia, in which the ovule was replaced by a leafy shoot which had made its way through a chink in the ovary. Inthis specimen, however, there was no evidence to show whether the shoot in question was a perverted development of the nucleus, or whether it was wholly independent of the ovule.

Fig.148.—Floret ofGaillardia, showing leafy shoot occupying the place of the ovule.

From this occasional elongation of the nucleus, as well as from the foliar nature of the ovular coats, Prof. Alex. Braun arrives at the conclusion that the ovule is to be looked on as a bud, the ovular coatings, so often variable in number, representing the scales of the bud, the nucleus corresponding to the end of the axis or growing point. Griffith had previously expressed the same opinion from his observations on malformed ovules ofSinapisandLonicera, while Caspary's conclusions from the foliaceous ovules ofTrifolum repensare somewhat similar. The latter observer considers that the funiculus, with the integuments, is the equivalent of a leaflet, the petiolule or midrib of which answers to the funiculus, and its hollow expansion to the integument. The nucleus itself is considered to be a new formation analogous to a shoot.

M. van Tieghem's conclusion[278]from the examination, of flowers ofTropæolum majus, in which the ovules were replaced by perfect peltate leaves, is that the ovules are foliar productions springing, not directly from a prolonged floral axis, as inPrimulaceæ, but from branches of the axis arising from the axils of the carpellary leaves.

Phyllody of the ovules has been met with most often in the following species:

*Aquilegia vulgaris!Skinneri.Delphinium crassicaule.elatum.dictyocarpum.Ajacis.Nigella damascena.Adonis autumnalis.Cheiranthus Cheiri!Nasturtium, sp.Sisymbrium officinale!Brassica napus!*olcracea!*Alliaria officinalis!Sinapis arvensis!Turritis, sp.Thlaspi arvense.Erucastrum Pollichii.Stellaria media.*Reseda lutea.Drosera intermedia.Agrostemma Githago.Stellaria media.Triumfetta, sp.!Tropæolum majus!Dictamnus albus.Fraxinella!Caram caruiPastinaca sativa.Torilis anthriscus.Thysselinum palustre.Epilobium palustre.Rosa, sp.Fragaria alpina.*Trifolium repens!Medicago maculata.Desmodium canadense.Melilotus macrorhiza.Lonicera, sp.Gaillardia!Crepis, sp.Phyteuma odorata.Symphytum Zeyheri.*officinale.Stachys sylvatica.Anagallia arvensis.phœnicea.Lysimachia ephemerum.*Primula sinensis!Auricula.prænitens.Gilia glomeruliflora.Rumex arifolius.scutatus.Salix capræa.

The following list of publications relating to ovular malformations is copied from A. Braun, 'Ueber Polyembryonie und Keimung von Cælobogyne' (Appendix),[279]to which are also added some others not alluded to bythat author and not specially referred to in the preceding pages:

Jaeger, 'Missbilld. d. Gewächse,' p. 78, 79, f. 47. Rœper, 'Enum. Euphorb.,' 1824. p. 45,Delphinium.—Schimper, 'Flora,' 1829, pp. 437–8, et 'Mag. fur Pharmacie de Geiger,' 1829–30, pl. iv-vi, text wanting,Primula,Reseda,Cheiranthus.—Engelmann, 'De Antholysi,' 1832.—Valentin, 'Act. Acad. Nat. Cur.,' 1839, p. 225,Lysimachia.—Unger, 'Act. Acad. Nat. Cur.,' xxii, 11, 1850, p. 543, t. 5B,Primula.—'Flora (B. Z.)', 1842, p. 369, t. ii,Trifolium.—Brongniart, 'Ann. Sc. Nat.,' 1834, ii, p. 308; also 'Archives Mus. d'Hist. Nat.,' 1844, t. iv, p. 43, pl. iv, v,Primula.—Reissek, 'Linnæa,' xvii, 1843,Alliaria.—Wydler, 'Denkshrift. d. Regensb. Bot. Gesell.,' 1855, iv, s. 77, t. vii,Alliaria.—Wigand. 'Grundlegung der Pflanzen Teratol.,' 1850, p. 39,Turritis.—Wigand, 'Bot. Untersuchungen,' 1853, p. 23,Rosa,Turritis,Crepis.—Germain de St. Pierre, 'L'lnstitut,' 1853, n. 1051, p. 351.—Rossmann, "Entwicklung der Eiknospen aus dem Fruchtblatte," &c., 'Flora,' 1855, pp. 647 and 705.—Dareste, 'Ann. Sc. Nat.,' 1842, p. 220,Delphinium.—Fresenius, 'Mus. Senkenb.,' ii, p. 39, t. iv, f. 9,Primula.—Schultz, 'Flora o. d. Bot. Zeit.,' 1834, xvii, p. 121,Nasturtium.—Seringe and Heyland, 'Bull. Bot.,' 1–7,Diplotaxis.—Clos, 'Mem. Acad. Toulouse,' vi, 1862,Delphinium.—Morren, C., 'Bull. Acad. Belg.,' xix, part ii, p. 519,Primula.—Caspary, 'Schrift. d. Physik. Œk. Gesell. zu Königsberg,' band ii, p. 51, tabs. ii, iii. Fleischer, 'Ueber Missbildungen Verschiedener Cultur Pflanzen.,' &c., Esslingen, 1862. Cramer, 'Bildungsabweich,' p. 68, &c. &c.,Trifolium.—Moquin-Tandon, 'El. Terat. Veg.,' p. 206,Cortusa.—Guillard, 'Bull. Soc. Bot. Fr.,' 1857, vol. iv, p. 761,Stellaria.—Moelkenboer, 'Tijdschrift v. Natuurl. Geschied.,' 1843, p. 355, t. vi, vii,Primula.—Van Tieghem, 'Bull. Soc. Bot. Fr.,' 1865, p, 411,Tropæolum.

Phyllody in accessory organs.—In addition to the ordinary organs of the plant, what are termed the accessory organs, such as hairs, spines, &c., sometimes become foliaceous. It is not to be wondered at that spines, when they represent the framework of a leaf, become sometimes clothed with cellular tissue, and thus become indeed true leaves. This happens occasionally inBerberis;a similar thing occurs in the stipules of someLeguminosæ; the scales of some begonias; the tendrils ofBignonia,Cobæa, &c.

The presence of two small green laminæ on the outer side of the two posterior stamens inAntirrhinum majushas also been met with. The adventitious organs appeared as if they were developments from the thalamus—a kind of foliaceous disc, in fact.

Fig.149.—Leafy petal ofEpilobium.

Fig.150.—Chloranthy, &c.Epilobium hirsutum.

Chloranthy.—The term phyllomorphy is applied to the individual parts of the flower which assume the form and appearance of leaves. By chloranthy it is to be understood that all, or the great majority of the organs of the flower assume these conditions.[280]In chloranthy, as here defined, there is no unusual number of buds, as there is in prolification, but the appearance of the flower-bud is so changed as to make it resemble more closely a leaf-bud than a flower-bud. There is not necessarily any increase in the number, or any alteration in the position of the buds, but the form and appearance of the latter differ from what is usual. Chloranthy, then, is a more complete form of frondescence. Owing to the vagueness with which the word has been applied by various authors, it becomes very difficult to ascertain whether the recorded instances of chloranthy were really illustrations of what is here meant by that term, or whether they were cases of mere virescence (green colour, without other perceptible change), or of prolification (formation of adventitious buds). It is, therefore, quite possible that some ofthe instances to be now mentioned were not strictly cases of chloranthy.

Fig.151.—a.Open leafy carpel of "green rose," with two deformed ovules.b.Ovule separate.c.Primine removed.d.Secondine and nucleus, with the bulbous end that projects through the micropyle.

Seringe[281]has described a malformation inDiplotaxis tenuifoliain which all the floral organs were replaced by sixteen distinct leaflets which had preserved their proper relative position. TheCruciferæ, of which family the last-named plant is a member, are particularly liable to this malformation, as also are theRosaceæ, as will be seen from the following illustrations. Roses indeed often exhibit alterations of this kind as the commencement of prolification. There is also in cultivation a rose[282]called the green rose, "Rose bengale à fleurs vertes," in which all the parts of the flower are represented by leaves. One of the most remarkable features in this plant is, that the carpels have often two ovules on their margins. Now, Payer, in his "Organogénie," has shown that at a certain period of the development of the ordinary rose flower the ovary contains two collateral ovules, of which onebecomes in process of time suppressed.[283]Geum coccineumhas been found by Wigand with its flowers in this condition.[284]

Lindley[285]figures a very interesting illustration inPotentilla nepalensis, in which some of the flowers have their component parts leafy, in others the receptacle lengthens, till in extreme cases the whole of the floral apparatus is represented by a branch bearing a rosette of leaves.

A particular variety of the Alpine strawberry is also described as occasionally subject to this transformation. In these flowers the calyx remains normal, while all the other parts of the flower, even to the coating of the ovule, assume a leaf-like condition.[286]

AmongLeguminosæa partial leafy condition (frondescence), or a more complete degree of the same change, (chloranthy) is not infrequent, particularly inTrifolium repens. In this species the changes are so common, so various and important, that they may be alluded to in some little detail. M. Germain de Saint Pierre,[287]in commenting on the frequency with which the flowers of this plant are more or less frondescent, remarks that although all the flowers on one plant may be affected, they are all changed in the same manner, but on different specimens different degrees of transformation are found. In all the corolla and stamens are comparatively little removed from the ordinary form, the calyx and pistil, however, have a particular tendency to assume a foliar condition. The author just cited arranges the malformations of this plant under three heads, as follows:

1. Calyx-teeth larger than usual, sometimes dentate at the margin; petals more or less regular and disposed to run away from the papilionaceous form; filaments free; anthers normal; carpel transformed into a true leaf with a long stalk provided at the base, with two stipules, terminal leaflet, solitary, green, with no trace of ovules. Sometimes a second carpellary leaf, similar to the first, is formed; in other cases the central axis of the flower is occasionally prolonged into a head of young flowers—median prolification. In some few instances the calyx is not at all altered, but the carpellary leaf is trifoliolate, or even quinquefoliolate,the corolla being then absent. The heads of flowers in this first form have the aspect of little tufts of leaves.2. Each of the teeth of the calyx is represented by a long stalk, terminated by a single articulated leaflet, the bi-labiate form of the calyx is still recognisable; the two upper petals are united, the three lower separate; the tube of the calyx is not deformed and seems to be formed of the petioles of the sepals united by their stipules. In this second class of cases the corolla is papilionaceous, the filaments free, the carpellary leaf on a long stalk provided with stipules, its blade more or less like the usual carpel, with its margins disunited or more commonly united with the ovules in the interior, sometimes represented by a foliaceous, dentate primine only. In one case the carpel was closed above, gaping below, where it gave origin to several leaflets, the lower ones oval, dentate, like ordinary leaflets, the upper ones merely lanceolate, leafy lobes, representing the primine reduced to a foliaceous condition. Inflorescence—a head with leafy flowers on long stalks, which are longer at the circumference than in the centre.3. Calyx-teeth lance-shaped, acuminate; corolla more or less regular, arrested in its development and scarcely exceeding the tube of the calyx within which it is crumpled up; stamens but little changed; carpellary leaf on a short stalk, not exceeding the calyx tube, but the ovarian portion very long, and provided with abortive ovules.These three groups will be found to include most of the forms under which frondescence of the clover blossoms occurs, but there are, of course, intermediate forms not readily to be grouped under either of the above heads. Such are the cases brought under the notice of the British Association at Birmingham in 1849 by Mr. R. Austen, in some of which the petals and stamens even were represented by leaves.

2. Each of the teeth of the calyx is represented by a long stalk, terminated by a single articulated leaflet, the bi-labiate form of the calyx is still recognisable; the two upper petals are united, the three lower separate; the tube of the calyx is not deformed and seems to be formed of the petioles of the sepals united by their stipules. In this second class of cases the corolla is papilionaceous, the filaments free, the carpellary leaf on a long stalk provided with stipules, its blade more or less like the usual carpel, with its margins disunited or more commonly united with the ovules in the interior, sometimes represented by a foliaceous, dentate primine only. In one case the carpel was closed above, gaping below, where it gave origin to several leaflets, the lower ones oval, dentate, like ordinary leaflets, the upper ones merely lanceolate, leafy lobes, representing the primine reduced to a foliaceous condition. Inflorescence—a head with leafy flowers on long stalks, which are longer at the circumference than in the centre.

3. Calyx-teeth lance-shaped, acuminate; corolla more or less regular, arrested in its development and scarcely exceeding the tube of the calyx within which it is crumpled up; stamens but little changed; carpellary leaf on a short stalk, not exceeding the calyx tube, but the ovarian portion very long, and provided with abortive ovules.

These three groups will be found to include most of the forms under which frondescence of the clover blossoms occurs, but there are, of course, intermediate forms not readily to be grouped under either of the above heads. Such are the cases brought under the notice of the British Association at Birmingham in 1849 by Mr. R. Austen, in some of which the petals and stamens even were represented by leaves.

Although, on the whole, chloranthy is most frequent in the families already alluded to, yet it is by no means confined to them, as the examples now to be given amply show. Specimens ofNymphæa Lotushave been seen in which all the parts of the flower, even to the stigmas, were leafy, while the ovules were entirely wanting.

Planchon[288]figures and describes a flower ofDrosera intermediathat had passed into a chloranthic condition, excepting the calyx, which was unchanged; the petals, like the valves of the ovary, were provided with stipules, and were circinate in vernation.

M. A. Viaud-Grand-Marais[289]records an interesting example of chloranthy, in which the sepals, petals, pistils, and ovules ofAnagallis arvensiswere all foliaceous. Similar changes have not unfrequently been met with inDictamnus Fraxinella.

M. Germain de Saint Pierre has also recorded the following deviations in the flowers ofRumex arifoliusandR. scutatus; in these specimens the calyx was normal, the petals large, foliaceous, shaped like the stem-leaves, the stamens were absent, the three carpels fused into a triangular leafy pod, as long again as the perianth, the stigmas normal or wanting, the ovule represented by a thick funicle, terminated by a foliaceous appendage analogous to the primine.[290]

In grasses it frequently happens that the flowers are replaced by leaf-buds; this condition is alluded to elsewhere under the head of viviparous grasses, but in this place may be mentioned a less degree of change, and which seems to have been a genuine case of chloranthy inGlyceria fluitans, the spikelet of which, as observed by Wigand,[291]consisted below of the ordinary unchanged glumes, but the remaining paleæ as well as the lodicles and stamens were represented by ligulate leaves. The plant, it is stated, was affected by a parasitic fungus. On the other hand, General Munro, in his valuable monograph of theBambusaceæ,[292]refers to an illustration in which "the lowest glumes generally, and the lowest paleæ occasionally, had the appearance of miniature leaves, with vaginæ, ligules and cilia, enveloping, however, perfect fertile spiculæ; as progress is made towards the top of the spike, the ligule first, then the cilia, and finally, the leaf-like extension disappears, and the uppermost glumes assume the ordinary shape and form of those organs."

General remarks on chloranthy and frondescence.—Moquinremarks with justice that the position of the flowers on the axis is of importance with reference to the existence of chloranthy. Terminal flowers are more subject to it than lateral ones, and if the latter, by accident, become terminal, they seem peculiarly liable to assume a foliaceous condition. Kirschleger says, that inRubusthere are two sorts of chloranthy, according as the anomaly affects the ordinary flowering branches, or the leafy shoots of the year, the summits of which, instead of developing in the customary manner, terminate each in one vast and long inflorescence, very loose and indeterminate, and with axillary flowers.[293]

On the whole, taking in consideration cases of partial frondescence, as well as those in which most of the parts of the flower are affected, phyllody would seem to be most common in the petals and carpels, least so in the case of the stamens and sepals. It is more common among polysepalous and polypetalous plants than in those in which the sepals or petals are united together.

The causes assigned for these phenomena are chiefly those of a nature to debilitate or injure the plant; thus it has been frequently observed to follow the puncture of an insect. M. Guillard[294]gives an instance inStellaria mediawhere the condition appeared to be due to the attacks of an insectThrips fasciata. Still more commonly it arises from the attacks of parasitic fungi,e.g.Uredo candida, in Crucifers, &c.

In other cases it has been observed when the plants have been growing in very damp places, or in very wet seasons, or in the shade, or where the plant has been much trampled on. This happens frequently withTrifolium repens. The frequency with which the change is encountered in this particular species is very remarkable; it is difficult to see why one species should be so much more subject to the kind of change than another of nearly identical conformation.

It might at first be supposed that the same causes that bring about the complete substitution of leaf-buds for flower-buds (see Heterotaxy) would operate also in the partial substitution of leaves for other parts of the flower, but it will be seen that the inducing cause, whether similar or not in the two cases respectively, acts at different times; in the one case, it is not brought into play until the rudiments of the flower are already formed, whereas in the other the influence is exerted prior to the formation of the flower. So that while the formation of leaf-buds in place of flower-buds may be and generally is due to an excess of nutrition, inducing over activity of the vegetative organs, the production of phyllomorphic or chloranthic flowers may be owing rather to a perversion of development arising from injury or from some debilitating agency. The discrepancies in the assigned causes for the conditions above mentioned may, therefore, in great measure, be attributed to the different periods at which the causes in question operate.

The following list may serve as a guide to the plants most frequently the subjects of chloranthy, but reference should also be made to preceding and subsequent sections, and to that relating to prolification of the inflorescence.

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