Vegetable Teratology Part 24

In Bromfield's 'Flora Vectensis,' p. 35, the following account is given of an abnormal development in _Cardamine pratensis_: "On the lower part of the corymb were several seed vessels on pedicels changed from their usual linear to an ovate elliptical figure, so as to resemble a silicula. These, on being opened, were found to contain petals of the usual colour, which in the pods above had burst from their confinement and appeared as semi-double flowers; the valves of the pod answering to the true calyx. * * * From their verticillate arrangement it is evident that these petaloid expansions were not transformed seeds, but simply a development of the common axis within the ovary into an abortive whorl of floral organs, besides which there were evident rudiments both of stamens and germens in the centre of the bundle." Baillon[182] also records a case of the same nature in _Sinapis arvensis_.

[Ill.u.s.tration: FIG. 94*.--Portion of the interior of the silicle in _Cheiranthus Cheiri_, showing advent.i.tious pod in the place of an ovule.]

[Ill.u.s.tration: FIG. 95.--Advent.i.tious pod from fig. 94, enlarged.]

Here, too, may also be mentioned the presence of an advent.i.tious siliqua within the ordinary one attached along the same line as the ovules, and partially divided by a replum into two cavities. In this case there was nothing to indicate the presence of floral envelopes (figs. 94, 95). A similar occurrence has been brought under my notice in some grapes which were observed to be cracking before they were perfectly ripe, and in which advent.i.tious fruits were found within the parent grape, occupying the position of seeds (figs. 96, 97).

Similar anomalous growths are noticed under the heads of Subst.i.tution and Prolification.

=Formation of stamens within the cavity of the ovary.=--The only instance of this that has come under the author's observation occurred in some flowers of _Baeckea diosmaefolia_, Rudge, for an examination of which he is indebted to Mr. Bentham.

[Ill.u.s.tration: FIG. 96.--Section of Barbarossa grape showing advent.i.tious grape in the position of a seed.]

[Ill.u.s.tration: FIG. 97.--Grape with supplementary fruit in the interior]

In the normal flower there is a turbinate hollow calyx, whose limb is divided into five serrated lobes; alternating with these latter, and springing from the throat of the calyx, are the petals. Originating from the same annular disk as the petals are the stamens, seven or eight in number. The ovary is partially adherent, is surmounted by a style, and has two or three loculi with an axile placenta, to which several small curved ovules are attached. The malformed flowers did not present anything peculiar in their outer parts, nor did the ovary, partially immersed within the expanded top of the flower-stalk and the calyx-tube, which is continuous with that organ, show externally any indication of the change within. On cutting it across, however, in any direction, numerous perfect stamens (filaments and anthers) were seen projecting from the walls of the cavity (fig. 98). In most of the flowers the ovary was one-celled; but in a few there was the usual axile placenta; yet even in these latter cases the stamens originated from the walls of the cavity, and not from the placenta. The stamens presented different degrees of development; in some cases they were fully formed, the anther-lobes open, and the pollen exposed; while in other instances the filaments were involute or circinate, just as the ordinary stamens are in the unexpanded flower-bud. In some cases imperfect stamens were found, mere barren filaments, with or without rudimentary anthers at the top. In no instance was there a perfect ovule, or, indeed, any trace of ovules. The stamens appeared to be arranged irregularly on the walls of the ovarian cavity; and while they were certainly more numerous at the lower portion (that now generally considered to be formed by the cup-like end of the pedicel), they were not wanting in the upper half of the ovary (or that which is probably formed from the carpellary leaves).

[Ill.u.s.tration: FIG. 98.--1. Vertical section of flower of _Baeckea diosmaefolia_, showing stamens within the ovary; magnified ten times. 2.

Transverse section of ovary. 3. Stamen. 4. Imperfect stamen.]

This case differs from most that have been recorded, and in which there has been a more or less complete subst.i.tution of anther for carpel, or where the tissues of the carpel have produced pollen, and so taken upon themselves the appearance and functions of anthers. Instances of this latter kind are not uncommon; but in the _Baeckea_ there were perfect stamens proceeding from perfect and completely closed ovaries.

Moquin-Tandon[183] cites from Agardh an instance which seems more closely to resemble the state of things in the _Baeckea_, and which occurred in a double hyacinth, wherein both anthers and ovules were borne on the same placenta. Probably, though the fact is not stated, the ovary of the hyacinth was open; and we are told that the flower was double--that it was, in fact, modified and changed in more organs than one; while in the _Baeckea_ nothing at all unusual was observed till the ovary was cut open. The style was present even in those flowers where there was no axile placenta; hence in these cases it could not be, as Lindley stated it to be in the closely allied _Babingtonia_, a prolongation of the placenta.[184]

=Formation of pollen within the ovules.=--This has now been recorded in two instances by Mr. S. J. A. Salter in _Pa.s.siflora caerulea_ and in _P.

palmata_,[185] and by the author in _Rosa arvensis_.[186]

[Ill.u.s.tration: FIG. 99.--Pollen within the ovule of _Pa.s.siflora_ (after Salter).]

In the case of the pa.s.sion-flower there were various malformations in the ovaries, which were all more or less split open at the distal end, indicating a tendency towards dialysis. The pollen-bearing ovules were borne on the edges of these ovaries, and presented various intermediate conditions between anthers and ovules, commencing at the distal extremity of the carpel with a bi-lobed anther, and pa.s.sing in series to the base of the ovary, an antheroid body of ovule-like form, a modified ovule containing pollen, an ovule departing from a perfectly natural condition only in the development of a few grains of pollen in its nucleus, and, finally, a perfect, normal ovule.

In the flowers of the Rose the stamens exhibited almost every conceivable gradation between their ordinary form and that of the carpels, while some of the ovules contained pollen in greater or less abundance. Speaking generally, the most common state of things in these flowers was the occurrence on the throat of the calyx, in the position ordinarily occupied by the stamens, and sometimes mingled with those organs, of twisted, ribbon-like filaments, which bore about the centre one or more pendulous, anatropous ovules on their margins. Immediately above the latter organs were the anther-lobes, more or less perfectly developed, and surmounting these a long style, terminating in a fringed, funnel-shaped stigma. Sometimes the ovules were perfect, at other times the nucleus protruded through the foramen, while in a third set the nucleus was included within the tegument, the ovules having in all respects their natural external conformation, containing, however, not only pollen-grains, but also a layer of those peculiar spheroidal cells, including a fibrous deposit, which are among the normal const.i.tuents of the anther. In one case, where the coat of the ovule was imperfect, and allowed the nucleus to protrude, the pollen was evidently contained within the central ma.s.s of the structure. In this instance the fibrous cells were not detected, these being only found in cases where the investment of the ovule was perfect; and hence it seems likely that the fibrous cells were part of the coat of the ovule, while the pollen was formed within the nucleus. In no case was any trace of embryo sac to be seen.

The main interest, as Mr. Salter remarks, in these cases is physiological; so far as structure alone is concerned, there does not appear any reason why pollen-grains should not be developed in any portion of the plant; the mother cells in which the pollen is formed not differing, to all outward appearance, from any other cells, unless it be in size.

The fundamental unity of construction in all the organs of plants could hardly be better ill.u.s.trated than by these cases; while, in spite of their exceptional nature, they must be of great interest physiologically, as showing the wide limits of possible variation which thus may even involve the s.e.x, "for an ovule to develop pollen within its interior," says Mr. Salter, "is equivalent to an ovum in an animal being converted into a capsule of spermatozoa. It is a conversion of germ into sperm, the most complete violation of individuality and unity of s.e.x. * * * * The occurrence of an antheroid ovule and a normal ovule on the same carpellary leaf realises the simplest and the most absolute form of hermaphroditism."

It must, however, be remarked that the term subst.i.tution would be preferable to conversion. There is, at present, no evidence to show that the germinal vesicles were present in these cases; on the other hand, it seems most probable that they were not, so that the presence of the pollen-cells must be considered as simply advent.i.tious. It can hardly be that they were, in the first instance, germinal vesicles, which, in course of time, became so modified as to a.s.sume the appearance of pollen-grains. Between the nucleus of the ovule and the tubercle of cellular tissue const.i.tuting the primordial anther, there is little or no difference, so that it may be said that, for a time, there is no distinction of s.e.x in the nascent flower, but as development goes on, the difference becomes perceptible. It cannot at present be stated what precise circ.u.mstances induce the one ma.s.s to form mother-cells and pollen-grains, and the other to develop an embryo sac and germinal vesicles. Position and external circ.u.mstances may have some indirect effect, and it may, perhaps, be significant that in all the instances of polliniferous ovules, the ovular structures have been exposed on an open carpel or otherwise, in place of being confined within the cavity of a closed ovary, as under ordinary circ.u.mstances. Even among Conifers the ovuligerous scales are so closely packed that there is little or no exposure of the ovules. But, apart from all speculative notions as to the relation between the structure and functions of the anther and of the ovule respectively, and of the possibility or the reverse of parthenogenesis, it will clearly be necessary in any future alleged occurrence of the latter phenomenon to ascertain whether any or all of the apparent ovules are, or are not, anthers in disguise.

=h.o.m.omorphic flowers of "Compositae."=--In a large section of the _Compositae_ there is, as is well known, a distinction between the florets of the "disc" and those of the "ray," the latter being ligulate, the former tubular.

In what are erroneously called double flowers in this order, _e.g._ in the Chrysanthemum, Dahlia, &c. &c., the florets are all ligulate. This change is sometimes cla.s.sed with peloria, but there is no abnormal regularity in these cases. On the other hand, were the ligulate florets to be all replaced by tubular ones, the term peloria would be more strictly applicable. It will be remembered that in the sub-order _Liguliflorae_, the florets are naturally all ligulate, so that the change above mentioned is not in itself a very grave one.

=Heterotaxy affecting the inflorescence.=--Under the head of Prolification, Heterogamy, &c., various deviations from the normal inflorescence are alluded to. In this place, therefore, it is only necessary to mention certain rare deviations from the customary arrangement of the inflorescence, such as the change from a definite centrifugal form of inflorescence to an indefinite centripetal one. This occurs occasionally in roses, where the shoot, instead of terminating in a flower-bud, lengthens and bears the flower-bud on its sides as in a raceme.

In the hyacinth, the inflorescence of which is properly indefinite, the terminal flower may frequently be found to expand first, though in order of development it may have been the last formed.

It occasionally happens that certain plants will, contrary to their usual custom, bloom twice in the same season; this usually arises from the premature development of buds which, under ordinary circ.u.mstances, would not unfold till the following spring. In these instances of what the French term "fleuraison anticipee," the position of inflorescence is not changed, but there are other cases where the position of the inflorescence is altered, as in the laburnum, where, in some seasons, racemes may be seen springing from short lateral "spurs" along the sides of the branches, as well as from the extremities of long shoots.

Of a similar nature are those cases wherein stems or branches usually sterile become fertile; this happens in _Equisetaceae_,[187] in _Restiaceae_, and other orders. In the equisetums, the condition in question has been specially noticed to occur after prolonged drought.

_Equisetaceae_ are likewise subject to an anomaly called by Duval Jouve interruption of the spike, and wherein the scales bearing the spore cases are separated by whorls of branches instead of forming one compact unbroken spike as usual.

This alternation of the organs of vegetation and reproduction may also be seen occasionally in _Typha_, and other plants.

Kirschleger describes a case in which the male catkins of _Salix cinerea_ were placed at the ends of the branches instead of being lateral productions; moreover the usual articulation was not formed, so that the catkin was persistent instead of deciduous.[188]

=Supra-soriferous ferns.=--In the great majority of ferns the sori or cl.u.s.ters of spore cases are placed on the under surface of the fronds; nevertheless, a few cases are on record where the fructification is produced on the upper as well as on the lower surface, and sometimes abundantly so. This occasionally happens from the elongation of the normally placed sorus, which thus extends to the margin, and returns on the upper side, when the sori chance to be placed opposite to the marginal crenatures. But it is also frequently the case that the sori are produced on the upper side, distinctly within the margin, and where there are no corresponding sori beneath. Those varieties which have the margin crenated or lobed seem most liable to a.s.sume this abnormal supra-soriferous condition. Among the ferns in which this condition has been observed are the following: _Scolopendrium vulgare_, _Polypodium anomalum_, Hook., _Asplenium Trichomanes_, _Cionidium Moorei_.[189]

FOOTNOTES:

[147] 'Gard. Chron.' 1852, p. 51.

[148] 'Flora.' 1858, pp. 32-42.

[149] 'Journ. Linn. Soc.,' vol. vi; "Botany," 1862, p. 24.

[150] 'Tijdschrift voor Natuur. Geschied,' 1836, vol. iii, tab. vii, p.

171.

[151] Roeper, 'Enum. Euphorb.,' p. 19. Bernhardi, 'Linnaea,' vii, p.

561, tab. xiv, f. 1. Wydler, "Subcotyled. sprossbildung," 'Flora,' 1850, p. 337. Hooker, 'Trans. Linn. Soc.,' vol. xxiv, p. 20 (_Welwitschia_).

[152] 'Misc. Austriac. ad Bot.,' vol. i, p. 133, t. 5.

[153] See also Carriere, 'Revue Horticole,' 1866, p. 442; and as to pears, Radlkofer in 'Bericht uber die Thatigkert der Baierischen Gartenbau Gesellschaft,' 1862, p. 74, t. i.

[154] 'Flora Indica,' p. 23.

[155] 'Bull. Soc. Bot. Fr.,' 1856, p. 53.

[156] 'Trans. Linn. Soc.' xxvi, p. 142, tab. iv, B.

[157] "Si arbusculam, quae in olla antea posita, quotannis floruit et fructus protulit, deinde deponamus in uberiori terra calidi caldarii, proferet illa per plures annos multos ac frondosos ramos, sine ullo fructu. Id quod argumento est, folia inde crescere, unde prius enati sunt flores; quemadmodum vicissim, quod in folia nunc succrescit, id, natura ita moderante, in flores mutatur, si eadem arbor iterum in olla seritur."--Linnaeus, 'Prolepsis,' -- iii.

[158] 'Rev. Hortic.' May, 1868, 'Gardeners' Chronicle,' 1868, pp. 572, 737.

[159] Cited in 'Annals Nat. Hist.,' 1845, vol. xv, p. 177.

[160] 'Ann. Scienc. Nat.,' vol. xiv, 1860, p. 13.

[161] Naudin, 'Ann. Sc. Nat.,' 2nd ser., 1840, vol. xiv, p. 14, fig. 6, pl. i (_Drosera_). St. Hilaire, 'Comptes Rendus,' ix, p. 437.

[162] Hance, 'Hook. Journ. Botany,' 1849, vol. i, p. 141, pl. v.

[163] Booth, 'Gard. Chron.,' Jan. 1st, 1853, p. 4.

[164] Lindley, 'Theory of Horticulture,' ed. 2, p. 273.

[165] 'Hook. Journ. of Botany,' 1852, iv, p. 206. See also the curious _Begonia gemmipara_, 'Hook. fil. Ill.u.s.t. Himal. Plant.,' t. xiv.