FOOTNOTES:

[244] See Goethe, 'Versuch. der Metam. der Pflanzen,' 1790. English translation by Emily M. Cox, in Seemann's 'Journal of Botany,' vol. i, 1863, p. 327. For a brief sketch of the origin and progress of the theory of vegetable morphology, prior to the publications of Wolff, Linné, and Goethe, as well as for an attempt to show what share each of these authors had in the establishment of the doctrine, the reader is referred to an article in the 'Brit. and For. Medico-Chirurgical Review,' January, 1862, entitled "Vegetable Morphology: its History and Present Condition," by Maxwell T. Masters.

CHAPTER I.
PHYLLODY.

This condition, wherein true leaves are substituted for some other organs,[245] must be distinguished from Virescence, q. v., in which the parts affected have simply the green colour of leaves, without their form or structure. The appearance of perfect leaves, in place of other organs, is frequently looked on as due to retrograde metamorphosis, or to an arrest of development. But this is not strictly correct; for instance, suppose a petal, which is very generally merely the sheath of a leaf, with the addition of colouring matter, to be replaced by a perfect leaf, one in which all three constituent parts, sheath, stalk, and blade, are present, it surely can hardly be said that there has been any retrogression or arrest of development in the formation of a complete in place of an incomplete organ. The term retrograde here is used in a purely theoretical sense, and cannot be held to imply any actual degradation. Morphologically, as has been stated, the case is one of advance rather than the reverse, and hence the assignment of instances of this nature to a perversion of development, rather than to a diminution or to an exaltation of that process, seems most consistent with truth. The affected organs have really undergone no actual change, simply the direction of the organising force has been altered at a very early state, so that the usual differentiation of parts has not taken place.

Fig. 126.—'Rose plantain,' Plantago media var., spike contracted; bracts leafy.

Phyllody of the bracts.—As bracts are very generally imperfect organs, so their replacement by perfect leaves is not attributable to arrest of development or retrograde metamorphosis, but the reverse. The bracts of some species of Plantago[246] are very subject to this change. Thus, in the rose plantain of gardens, P. media (fig. 126), the bracts are leafy and the axis depressed or not elongated, so that it is surmounted by a rosette of small leafy organs. A similar condition of the bracts, unattended with arrest of growth in the axis, is common in P. major (fig. 127) and in P. lanceolata ([see p. 108]). It also occurs in the bracts of Corydalis solida, Amorpha fruticosa, Ajuga reptans, Parthenium inodorum, Centaurea Jacea, in the involucral bracts of the dandelion, the daisy, and many other composites. In the 'Gardeners Chronicle,' 1852, p. 579, is figured a dahlia in which the bracts of the involucre and the scales of the receptacle had all assumed the form, texture, and venation of leaves.[247]

Fig. 127.—Leaf-like bracts in Plantago major.

Fig. 128.—Dahlia. Scales of receptacle leafy.

In Umbelliferæ the substitution of leaves for involucral bracts is not infrequent. It has been observed among other plants in Angelica Razoulzii, Carum carui, Daucus Carota, &c. The scales of the hop (Humulus Lupulus) not infrequently manifest this change, as do also the bracts of many amentaceous plants, e.g. in the male catkins of the walnut, the female catkins of the alder,[248] of some willows,[249] &c. The bracts of some Euphorbiaceæ, as E. pusilla, E. Lathyris, E. Cyparissias, have been observed to undergo a similar alteration.[250]

Amongst monocotyledons an analogous change occurs not unfrequently, as in some commelynaceous plants, e.g. Tradescantia, in Musa, &c.

The spathe of Arum maculatum is sometimes represented by a stalked leaf similar to that which occurs, under ordinary circumstances, in Spathiphyllum, but in which genus the spadix is more or less adherent to the leaf-like spathe.[251] In Schœnus cephalotes a similar exaggerated development of the bracts is figured by Rottboell.[252]

Phyllody in inflorescence of Conifers.—This demands passing notice by reason of the interest attaching to the morphological construction of these plants. The elongation of the axis which occurs in the female cones has been already alluded to under the head of prolification of the inflorescence. This change is frequently associated with a more or less foliaceous condition of the bracts, which, indeed, may be seen to be serially continuous, both above and below, with the ordinary leaves. The scales, too, become notched and bipartite, and show, between the lobes, the rudiment of a bud, which in a further stage becomes developed into a shoot bearing leaves. Such a change has been described by Parlatore in Abies Brunoniana, and examples may frequently be met with in the larch (Larix europæa), and specially in Cryptomeria japonica.[253] The scales of the male catkins of conifers likewise occasionally assume the appearance of leaves; this may be seen in monstrous catkins of Araucaria, as also in Podocarpeæ and Cupressineæ (Eichler).

Phyllody of the calyx.—Sepals under ordinary circumstances are so like leaves, that it is not wonderful that they are often replaced by those organs.[254] A singular instance of this has been mentioned as occurring in Cakile maritima, wherein the sepals were found by M. Fournier to be pinnatifid like the ordinary leaves of the plant.[255] The sepals of Ranunculaceæ and Rosaceæ, for example, Rosa, Geum, are particularly liable to this change.

Fig. 129.—Flower of rose, sepals replaced by five perfect leaves; axis prolonged through the flower in the form of a leafy branch.

In a species of Geranium recently examined the sepals presented themselves in the form of three-lobed leaflets; so in fuchsias and in Epilobium hirsutum the sepals occasionally are not distinguishable from ordinary leaves (fig. 130). In roses, the change in question is a very frequent accompaniment of prolification (fig. 129). In the peach also this replacement of the sepals is sometimes carried to such an extent, that five perfect, bistipulate leaves occur in the place of the calyx, but when this is the case it usually happens that the pistil is abortive.

Fig. 130.—Fuchsia, with one of the sepals leaf-like.

De Candolle[256] figures a curious instance wherein the pappus of Podospermum laciniatum was replaced by five linear, foliaceous lobes. A similar change has been noticed in other composites, as in Tragopogon pratense. Engelmann mentions as subject to this hypertrophy of the pappus, as it may be termed, Scorzonera octangularis and Senecio vulgaris. Wigand has observed a similar transformation in a species of Centranthus (Valerianaceæ).

In some cases the phyllody of the sepals has a special interest, as bearing on the question whether what is termed calyx-tube is or is not a portion of the calyx, and whether the sepals are modifications of the blade or of the sheath of the leaf. Thus in the primrose the phyllodic sepals seem to show clearly that the sepals are in that plant of a laminar nature (fig. 131). The so-called calyx-tube of roses is elsewhere alluded to. The leaf-like organs sometimes seen at the apex of a cucumber would seem to support the view that there was really a calyx-tube in Cucurbitaceæ adherent to the carpels. It is also shown in the cut, fig. 132, borrowed from the 'Gardeners' Chronicle,' 1859, p. 654.

Fig. 131.—Primrose. Calyx of foliaceous segments.

Fig. 132.—Leafy calyx of melon.

Under ordinary circumstances, the sepals may be considered as the representatives of the sheath of the leaf (cataphyllary) or of the blade (euphyllary), the arrangement of the veins being different in the two cases; thus, in the vagina or sheath, there are generally several large veins of about equal size, either convergent towards the apex, or divergent; on the other hand, in the blade, there is usually but one central vein, the midrib, larger than the rest, and the smaller veins come off at a less acute angle, and are more reticulated.[257]

Now, when phyllomorphy occurs in sepals which ordinarily are vaginal, it is obvious that the case is one, not merely of increased relative growth, but also of the appearance or development of an organ habitually suppressed; on the other hand, when phyllomorphy occurs in sepals which usually are laminar in form and nervation, the case is one of unusual growth or hypertrophy, and not of the development of an organ habitually suppressed, so that the amount of change is greater in the former than in the latter instance.

Under normal circumstances it will be found that laminar venation is most common in gamosepalous and vaginal venation in polysepalous calyces. And the same holds good in cases where the calyx is abnormally leafy. The complete leaf development shows itself more frequently among the monosepalous plants than in the polysepalous ones, as shown even in the subjoined list of species. This statement would be more fully verified were it possible to state the frequency with which the condition occurred in individual plants, when it would be found that phyllody of the calyx occurs much more often in individual gamosepalous plants than in polysepalous ones.

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

Consult also Turpin, 'Atlas de Goethe,' t. iv, f. 12, Lycium. Engelmann, 'De Anthol.,' § 35, p. 31. This author figures phyllodic sepals in Senecio vulgaris, tab. v, figs. 24–26; Campanula, tab. iii, f. 15, 16; Athamanta cervaria, tab. v, f. 14. Lindley, 'Elements of Botany,' 1847, pp. 64, 73, &c. 'Gard. Chron.,' 1858, p. 685; 1859, p. 654, Cucurbita. Petunnikoff, 'Bull. Soc. Imp. Moscow,' 1862, Cirsium. Braun, 'Rejuvenescence,' Ray Society's Transl. See succeeding paragraphs.

Phyllody of the corolla.—The petals also are frequently replaced by leaves, though in many of the recorded instances the change has been one of colour only; these latter are strictly cases of virescence. M. Seringe[259] speaks of a flower of Peltaria alliacea in which the calyx was petal-like, while the corolla was leafy as if there had been transposition of the two organs, a very rare, if not unparalleled, instance. In a flower of Campanula Medium, provided, as is often the case, with a double corolla, the outer corolla was slit down on one side, the edges of the cleft being leafy.

Fig. 133.—Sepals and petals to leaves. Geranium.

The frondescent petals are very often completely disjoined, as in Verbascum nigrum, and Lonicera Periclymenum, in which, moreover, median prolification generally coexists. In the case of Tropæolum majus, the ordinary leaves of which are peltate and orbicular, the petals when frondescent have not the peltate arrangement, but are spathulate, and provided with very long, narrow stalks, so that, in some cases, they are, more properly speaking, enlarged virescent petals than true leaves; in other instances, however, the arrangement of the veins is more like that of the true leaves than that of the petals.

As might be expected, frondescence of the petals is frequently accompanied by other changes of a similar nature in other parts of the flower, and sometimes by the abortion of the sexual organs. Thus, in Actæa spicata, as observed by Fresenius, the petals were replaced by true petiolate, palminerved, lobed leaves, the stamens and pistils being abortive. In Ranunculus the leaves that appear in the place of the petals have no scale at their base, and in Tropæolum the calyx (or receptacle) is free from the usual spur.

The absolute frequency of this occurrence seems to be greatest in those flowers which are normally polypetalous. The petals of these flowers, as a general rule, are more like the leaf-sheaths than the leaf-blades as to their venation, hence it would seem that the phyllomorphic condition in these petals is a manifestation of a greater degree of organizing force than that which occurs in those cases where the petals are normally present in the form of contracted blades or laminæ. (See the remarks in the preceding section.)

Frondescence of the petals has been observed most frequently in the following cases; some, perhaps, were cases merely of virescence, q. v.; see also under Chloranthy, Prolification.

See Moquin-Tandon, 'El. Terat. Veg.,' p. 203. Engelmann, 'De Anthol.,' § 38 et 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 stamens happens 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 in Euphorbia 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 a Petunia, opened to show the stamens partially replaced by stalked leaves.

In the case of frondescent flowers of Tropæolum majus the 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.

In Jatropha Pohliana, Müll. (Adenorophium luxurians, Pohl.), a singular condition has been observed by M. Müller (Argov.). In this flower the anther, in place of 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 of Jatropha, after Müller (Arg.).

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

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

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, like S. platanifolia, which are foliaceous in texture and open very early in the course of their development. A similar occurrence has also been frequently noticed in the Columbine and also in Cruciferæ and Umbelliferæ. M. Germain de St. Pierre mentions an instance wherein the carpels of Salix Babylonica were converted into two leaves, provided with stipules. All the flowers of the catkins were 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 of Ranunculus and Anemone.

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 the Cucurbitaceæ is 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 of Anchusa ochroleuca were 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 of Triumfetta, 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 in Aquilegia; in other cases of the blade, as in Cerasus, Daucus, &c.

Fig. 139.—Flower of Triumfetta, 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 of Carduus heterophyllus and C. tataricus in 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 of Trifolium repens consisted 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 the flower. 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 the Umbelliferæ, 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 in Aquilegia, Delphinium, &c., on the edges of the carpel or on the surface, as in some flowers of Ranunculus repens and R. 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:

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 of Nigella and Adonis, 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. In Primulaceæ, 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 the ovules of Primula 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 in Primula 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 in Cortusa Mathioli, in which the funiculi bore little rounded leaves. Brongniart has described some malformations of Primula sinensis in which the ovules were transformed wholly or partially into small leaves with three to five lobes.[269] Dr. Marchand[270] mentions similar changes in Anagallis arvensis and Lonicera Periclymenum.

Cramer[271] figures ovules of Primula sinensis in 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 in Symphytum officinale wherein 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 as real in the cases now to be mentioned. In Sinapis and in Brassica oleracea foliaceous 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 in Sinapis,[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 in Trifolium 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 of Triumfetta ([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 of Trifolium 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 of Drosera 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 simple cup formed by the confluence of four glanduliferous hairs and the concave leaf and the perfect ovule.

Brongniart[275] records ovules of Delphinium elatum existing 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 in Aquilegia Skinneri; and another is figured in Lindley's 'Elements of Botany,' p. 88, f. 180.

Fig. 143.—Portion of an open foliaceous carpel of Delphinium, 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 ovules from 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 in Delphinium 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 of Dianthus, bearing ovules and carpels. 2. One of the ovaries separated.

Fig. 147.—Ovules of Dianthus passing 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 development of 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 at c, d, e. Could such a change occur in the animal kingdom, there would be the unfertilised ovum converted 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 of Alliaria officinalis, and Schimper has described and figured specimens of Nigella damascena in 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 of Gaillardia, in which the ovule was replaced by a leafy shoot which had made its way through a chink in the ovary. In this 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 of Gaillardia, 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 of Sinapis and Lonicera, while Caspary's conclusions from the foliaceous ovules of Trifolum repens are 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 of Tropæolum 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 in Primulaceæ, 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:

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 by that 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. 5 B, 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 in Berberis; a similar thing occurs in the stipules of some Leguminosæ; the scales of some begonias; the tendrils of Bignonia, Cobæa, &c.

The presence of two small green laminæ on the outer side of the two posterior stamens in Antirrhinum majus has 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 of Epilobium.

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 of the 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 in Diplotaxis tenuifolia in which all the floral organs were replaced by sixteen distinct leaflets which had preserved their proper relative position. The Cruciferæ, of which family the last-named plant is a member, are particularly liable to this malformation, as also are the Rosaceæ, 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 one becomes in process of time suppressed.[283] Geum coccineum has been found by Wigand with its flowers in this condition.[284]

Lindley[285] figures a very interesting illustration in Potentilla 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]

Among Leguminosæ a partial leafy condition (frondescence), or a more complete degree of the same change, (chloranthy) is not infrequent, particularly in Trifolium 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.

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 of Nymphæa Lotus have 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 of Drosera intermedia that 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 of Anagallis arvensis were all foliaceous. Similar changes have not unfrequently been met with in Dictamnus Fraxinella.

M. Germain de Saint Pierre has also recorded the following deviations in the flowers of Rumex arifolius and R. 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 in Glyceria 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 the Bambusaceæ,[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.—Moquin remarks 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 in Rubus there 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 in Stellaria media where the condition appeared to be due to the attacks of an insect Thrips 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 with Trifolium 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.

In addition to the publications before cited the following may be named as containing valuable information on the subject of this chapter.

Jæger, 'Missbild. Gewächs.,' 1814, p. 83, Trifolium repens. For other accounts of similar malformations in the same plant, see Schmitz, 'Linnæa,' xv, p. 268. Unger, 'Flora' (B. Z.) xxv, p. 369. Caspary, 'Schrift. der. Physik. ökon. Gesellsch. zu Königsberg,' 2, 1861, p. 51, tabs. ii, iii. Fleischer, 'Missbilld. verschied. Cult. Pflanz.,' 1862, p. 55, &c., t. v, vii, &c. For Primula see Brongniart, 'Ann. Sc. Nat.,' ser. 2, t. i, p. 308. A. P. and Alph. De Candolle in 'Neue Denkschrift.' Morren, C., 'Bull. Acad. Roy. Belg.,' xix, part 2, p. 539. Molkenboer, 'Tijdschr. voor Natuurl. Geschied.,' 1843, p. 355, tabs. vi, vii. Marchand, 'Adansonia,' iv, p. 167 and p. 159. Anagallis, p. 171, Lonicera, p. 83, Juncus. For other plants see Fresenius, 'Mus. Senk.,' 2, p. 35, &c. Norman, 'Ann. Sc. Nat.,' ser. 4, 1858, vol. ix, p. 220. Christ, 'Flora' (B. Z.) 1867, p. 376, tabs. v, vi, Stachys. Cramer, 'Bildungsabweich.,' p. 26, &c. Baillon, 'Adansonia,' ii, p. 300. Moquin-Tandon, 'El. Ter. Veg.,' p. 230. Schauer's translation, p. 220. Hallier, 'Phytopathologie,' p. 160.