Fig.198.—Regular dimerous flower ofCalanthe vestita.
Fig.198.—Regular dimerous flower ofCalanthe vestita.
Fig.199.—Regular dimerous flower ofOdontoglossum Alexandræ.
Fig.199.—Regular dimerous flower ofOdontoglossum Alexandræ.
Dr. Moore, of Glasnevin, kindly forwarded to the writer a flower ofCalanthe vestita(fig. 198), in which there were two sepals only, anterior and posterior, and two petals at right angles to the two sepals. The lip was entirely wanting, but the column and ovary werein their usual condition. InOdontoglossum Alexandræa similar reduction of parts has been observed by the author (fig. 199).
It is curious to observe in these flowers how precisely one sepal occupies the position of the labellum, and how the lateral petals are displaced from the position they usually occupy, so as to form a regular flower, the segments of which decussate, thus giving rise to a species of regular peloria.
The genusMæleniawas established on a malformed flower ofOrchisof similar character to those above mentioned.
Meiotaxy of the calyx.—As already mentioned, this term is here employed to denote those illustrations in which entire whorls are suppressed. Complete deficiency of the calyx in a dichlamydeous flower seems seldom or ever to occur; the nearest approach to it would be in those cases where the calyx is, as it is termed, "obsolete," but here it is chiefly the limb of the calyx which is atrophied, the lower portion being more or less adherent to the ovary. In what are termed monochlamydeous flowers both calyx and corolla are wanting, as inSalicineæand many other orders.
Meiotaxy of the corolla.—Deficiency of the entire corolla occurs in conjunction with similar reductions in other organs, or as an isolated phenomenon in the many apetalous varieties of plants recorded in books. Deficiency of the corolla was observed inCampanula perfoliataandRuellia clandestinaby Linné, who calls such bloomsflores mutilati.[480]Drs. Hooker and Thomson relate a similar occurrence inCampanula canescensandC. colorata. Some plants seem as a normal occurrence to produce flowers of different construction, and are hence termed dimorphic, as in manyMalpighiaceæ,Violaceæ,Oxalidaceæ, in some of the flowers of which the petals are altogether wanting, while in others thecorolla is developed as usual. This deficiency of the corolla is frequently, but not invariably, associated with an increased fertility. Thus, in some violets the flowers produced in summer, and in which the petals are either entirely suppressed or are more or less atrophied, are always fertile, while the blossoms developed in spring, and in which the petals are always present, are much less fertile. InOxalis Acetosellathere are two forms of flower, the one with, the other without, petals, but both seem equally fertile. Linné remarks that many plants which, in warm latitudes, produce a corolla, do not do so when grown in colder climates. Thus, certain species ofHelianthemumare apetalous in Lapland. In the Pyrenees, according to Bentham, the flowers ofAjuga ivaare constantly deprived of their corolla.[481]
Apetalous flowers have been noted most frequently in the following plants:
Aconitum, sp. pl.!Cardamine impatiens.Cheiranthus Cheiri!Viola odorata!Cerastium vulgatum!Alsine media.Stellaria.Lychnis dioica!Dianthus barbatus, and other Caryophylleæ.Helianthemum, sp.!Oxalis Acetosella.Balsamineæ.Malpighiaceæ.Rosa centifolia.arvensis!Cratægus!Medicago lupulina.Melilotus officinalis.Ononis minutissima.Saxifraga longifolia.Verbascum Thapsus.Ajuga iva.Teucrium Botrys.Lamium purpureum!amplexicaule.Polemonium cæruleum.Campanula, sp. pl.!Ruellia clandestina.Lonicera Periclymenum!Tradescantia, sp.!Hymenocallis.
The following references apply some to apetalous and others to dimorphic flowers, but it must be remembered that the latter plants are not necessarily wanting in petals or stamens, &c., though the functional activity of the parts may be impaired:A. de Jussien, 'Monogr. Malpigh.,' pp. 82, 334. Torrey, 'Fl. New York,' i, p. 428. Hooker and Thomson, 'Journ. Linn. Soc.,' ii, p. 7, Guillemin, 'Archiv. de Botan.,' i, p. 412. Michalet, 'Bull. Soc. Bot. Fr.,' vii. p. 465. Müller, 'Bot. Zeit.,' 1857, p. 729. 'Natural History Review,' July, 1862, p. 235.
The following references apply some to apetalous and others to dimorphic flowers, but it must be remembered that the latter plants are not necessarily wanting in petals or stamens, &c., though the functional activity of the parts may be impaired:
A. de Jussien, 'Monogr. Malpigh.,' pp. 82, 334. Torrey, 'Fl. New York,' i, p. 428. Hooker and Thomson, 'Journ. Linn. Soc.,' ii, p. 7, Guillemin, 'Archiv. de Botan.,' i, p. 412. Michalet, 'Bull. Soc. Bot. Fr.,' vii. p. 465. Müller, 'Bot. Zeit.,' 1857, p. 729. 'Natural History Review,' July, 1862, p. 235.
Meiotaxy of the andrœcium.—Complete suppression of the stamens occurs normally in the female flowers of unisexual plants, and, as an accidental occurrence, is not very uncommon.Erica Tetralixis one of the plants in which this is said to happen. The varietyanandrais said to have been known in France since 1635. Cornuti speaks of it in his 'Enchiridion.' In 1860 M. du Parquet discovered it in peaty woods near Nangis (Seine et Marne).
ManyUmbelliferæ, such asTrinia vulgaris, present a like deficiency, while it is of common occurrence amongRosaceæandPomaceæ. In the latter group the St. Valery apple, so often referred to, is an illustration. To obtain fruits from this variety it is necessary to apply pollen from another flower, a proceeding made the occasion of festivity and rejoicing by the villagers in some parts of France. In some of theArtemisias, especially inArtemisia Tournefortiana, all the florets have been noticed to be female, owing to the suppression of the stamens, and this suppression is associated with a change in the form of florets.[482]Mr. Moggridge has communicated to the author flowers ofThymus Serpyllumfrom a plant in which all the stamens were deficient, the flower being otherwise normal.
M. Dupont has given a list of nineteen species ofChenopodiaceæin which female flowers are occasionally produced, owing to the entire suppression of the staminal whorl.[483]
Flowers the subjects either of regular or irregular peloria,q. v., are often destitute of some or all their stamens,e.g.Calceolaria,Linaria,Viola, &c., while in cases of synanthy suppression of some of the parts of the flower, and specially of the stamens, is of very common occurrence.
Suppression of the andrœcium as a teratological occurrence has been most frequently noticed in thefollowing plants, omitting members of those families whose floral construction is normally incomplete in the majority of instances, and exclusive also of cases of substitution. See also under Heterogamy.
Ranunculus Ficaria!auricomus!bulbosus!Cruciferæ, sp. pl.Violaceæ, sp. pl.Honckenya peploides.Stellaria.Caryophyllaceæ, sp. pl.Malpighiaceæ, sp. pl.Tropæolum majus!Fragaria vesca!Rubus, sp.Pyrus Malus.Agrimonia vulgaris.Rosaceæ, sp. pl.Trifolium hybridum.repens.Umbelliferæ, sp. pl.Onagraceæ, sp. pl.Hippuris vulgaris.Callitriche vernalis.autumnalis.Lonicera Periclymenum.Erica Tetralix.Thymus Serpyllum.Calceolaria.Compositæ, sp. pl.Chenopodiaceæ, sp. pl.Stratiotes aloides.
Meiotaxy of the gynœcium.—Complete suppression of the pistil is of more frequent occurrence than that of the stamens, hence more flowers become accidentally unisexual by suppression of the pistil than by deficiency of the stamens.
In manyUmbelliferæ, e.g.Torilis Anthriscus,Cicuta virosa, the central flowers are often male, owing to the suppression of the pistil. In many double flowers, owing to the excessive multiplication of petaloid stamens, the pistil is suppressed, in which cases it often happens that the flower is depressed in the centre, as in some garden varieties ofRanunculus. Schlechtendal, in describing a flower ofColchicum autumnale, in which the perianth was virescent, says that, although the stamens were present, the pistil was absent.
In proliferous flowers the pistil is often completely defective, its place being occupied by the adventitious bud or axis.
As in other cases of like nature, suppression of the pistil is very frequently consequent on fusion of flowers or other changes. Thus Morren relates an instance of synanthy in the flowers ofTorenia scabra, accompanied by resorption or disappearance of some partsand spiral torsion of others. The pistil was entirely absent in this instance.[484]
M. Gaetano Licopoli places on record an instance where the petals and carpels ofMelianthus majorwere suppressed.[485]
On the whole, the pistil seems less subject to changes of this character than the andrœcium.
Suppression of the pistil has been most frequently recorded in flowers (normally bisexual) of—
Ranunculus!Aconitium!Delphinium!Pæonia.Caryophylleæ!Umbelliferæ.Trifolium repens.hybridum.Compositæ, sp. pl.Datura.Torenia asiatica.Colchicum autumnale.
Suppression of ovules,—abortion of seeds.—The two cases are taken together, as the effects are similar, though it must be remembered that in the one case the ovules at any rate have been formed, but their development has been arrested, while in the other they have never existed. The precise cause that has determined the absence of seed cannot in all cases be ascertained in the adult condition, hence it is convenient to treat the two phenomena under one head.
Many plants in other than their native climates either produce no fruit at all, or the fruits that are produced are destitute of seed,e.g.Musa,Artocarpus, &c. Some of the cultivated varieties of the grape and of the berberry produce no seeds.
Suppression or abortion of the seed is frequently associated with the excessive development either in size or number of other portions of the plant, or with an altered condition, as when carpels become foliaceous and their margins detached. Hybridisation and cross fertilisation are also well-known agents in diminishing the number and size of seeds.
Meiotaxy of the parts of the flower in general.—In the preceding sections suppression has been considered as it affected individual members of a whorl or separate whorls. It rarely happens, however, that the suppression is limited in this way. More generally several of the parts of the flower are simultaneously affected in the same manner.
A few illustrations are all that is necessary to give as to this point.
One of the most familiar instances is that of the cauliflower or broccoli, where the common flower-stalk is inordinately thickened and fleshy, while the corolla and inner parts of the flower are usually entirely suppressed; the four sepals can, however, generally be detected.
Maximowicz describes aStellaria(Kraschenikovia) in which the upper flowers are male only, while the lower ones, which ultimately become buried in the soil, have neither petals, stamens, nor styles, but the walls of the capsule are fleshy, and enclose numerous seeds.[486]
Kirschleger[487]mentions a variety ofLonicera Caprifolium, which was not only destitute of petals but of stamens also.
In some species ofMuscariandBellevaliathe uppermost flowers of the raceme show more or less complete suppression of almost all the part of which the flower normally consists. In those cases where an imperfect perianth exists, but in which the stamens and pistils are entirely suppressed, Morren applies the term Cenanthy,κενος, empty.
Complete suppression of the flower.—It is not necessary in this place to allude to that deficient production of flowers characteristic of what is termed by gardeners a "sky bloomer." In such plants often the requisite conditions are not complied with, and the skill of thegardener is shown in his attempt to discover and allow the plant to avail itself of the necessary requirements. We need here only allude to those instances in which provision is made for the production of flowers, and yet they are not produced. A good illustration of this is afforded by the feather-hyacinth,Hyacinthus comosus, in which the flowers are almost entirely suppressed, while the pedicels are inordinately increased in number, and their colour heightened. Something similar occurs in several allied species, and inBowiea volubilis. The wig plant (Rhus Cotinus) affords another illustration of the same thing. Some tendrils also owe their appearance to the absence of flowers, being modified peduncles; proofs of this may frequently be met with in the case of the vine.
InLamium albumI have seen one of the verticillasters on one side of the stem completely wanting, the adjacent leaf being, however, as fully formed as usual.
General remarks on suppression.—On comparing together the various whorls of the flower in reference to suppression, and, it may be added, to atrophy, we find that these phenomena occur most rarely in the calyx, more frequently in the corolla, and very often in the sexual organs and seeds; hence it would seem as if the uppermost and most central organs, those most subject to pressure and latest in date of development—formed, that is, when the formative energies of the plant are most liable to be exhausted—are the most prone to be suppressed or arrested in their development. When the plants in which these occurrences happen most frequently are compared together, it may be seen that partial or entire suppression of the floral envelopes, calyx, and corolla, is far more commonly met with in the polypetalous and hypogynous groups than in the gamopetalous or epigynous series.
The orders in which suppression (speaking generally) occurs most often as a teratological occurrence are thefollowing:—Ranunculaceæ,Cruciferæ,Caryophyllaceæ,Violaceæ,Leguminosæ,Onagraceæ,Jasminaceæ,Orchidaceæ. It will be observed that these are all orders wherein suppression of the whole or part of the outer floral whorls takes place in certain genera as a constant occurrence.
Again, it may be remarked that many of these orders show a tendency towards a regular diminution of the assumed normal number of their parts; thus, amongOnagraceæ,CirceiaandLopeziamay be referred to, the former normally dimerous, the latter having only one perfect petal. So in fuchsias, a very common deviation consists in a trimerous and rarely a dimerous symmetry of the flower.
Although, if the absolute number of genera or orders be counted, there appears to be little difference in the frequency of the occurrence of suppression in irregular flowers as contrasted with regular flowers, yet if the individual instances could be counted in the two groups respectively it would be found that suppression is more common among irregular than in regular flowers. Thus, the number of individual instances of flowers in which the perianth is defective is comparatively large amongViolaceæ,Leguminosæ, andOrchidaceæ. This statement hardly admits of precise statistical proof; still, it is believed that any observer who pays attention to the subject must come to the same conclusion. This is but another illustration of the fact that conditions which are abnormal in one plant constitute the natural arrangement in others.
As to the suppressions that occur in the case of the sexual organs, and the relations they bear to dimorphism, diclinism, &c., but little stress has been laid on them in this place, because their chief interest is in a physiological point of view, and is treated of in the writings of Mohl, Sprengel, Darwin, Hildebrand, and others. All that need be said here is, that teratology affords very numerous illustrations of those intermediate conditions which are also found, undernatural circumstances, between the absolutely unisexual flowers, male or female, and the structurally hermaphrodite ones. Rudimentary stamens or pistils are of very common occurrence in monstrous flowers. See Chapter on Heterogamy, &c.
FOOTNOTES:[465]'Rev. Hortic.,' 1866, p. 467.[466]De Rochebrune, 'Bull. Soc. Bot. Fr.,' ix, p. 281. The author points out seven grades between complete absence of petals and their presence in the normal number in this plant. See also Gaudin, in 'Koch. Fl. Helv.;' Koch. 'Synops. Fl. Germ.;' Cramer, 'Bildungsabweich,' p. 85.[467]'Bull. Acad. Belg.,' t. xix, part 1, p. 255.[468]'Bull. Bot.,' i, p. 7, tab. i, f. 7.[469]See Gay, 'Ann. Sc. Nat.,' iii, p. 27.[470]'Ann. Sc. Nat.,' 4 ser., v, p. 305.[471]Cramer, 'Bildungsabweich,' p. 90.[472]See also Clos, 'Bull. Soc. Bot. Fr.,' xiii, p. 96, adnot.[473]See Cramer, 'Bildungsabweich,' p. 7. Hildebrand, 'Bot. Zeit.,' xx, 1862, p. 209.[474]See Hildebrand, 'Bot. Zeit.,' xx, 1862, p. 209.[475]'Bull. Soc. Bot. Fr.,' viii, p. 287.[476]'Bull. Soc. Bot. Fr.,' vol. viii, 1861, p. 152.[477]Ibid., ix, p. 275.[478]Ibid., 1861, vol. viii, p. 149.[479]'Lobelia,' p. 55.[480]'Phil. Bot.,' p. 119.[481]'Cat. Plant. Pyr,' p. 58.[482]Moquin-Tandon, loc. cit., p. 328.[483]For other instances see Chatin in 'Ann. Sc. Nat.,' 4 ser., vol. v, p. 305.[484]See also Morren. 'Bull. Acad. Belg.,' xv, Fuchsia, p. 67.[485]Cited in 'Bull. Soc. Bot., France,' t. xiv ("Rev. Bibl."), p. 253.[486]'Primit. Flor. Amurens.' p. 57.[487]'Flora.' 1848. p. 484.
[465]'Rev. Hortic.,' 1866, p. 467.
[465]'Rev. Hortic.,' 1866, p. 467.
[466]De Rochebrune, 'Bull. Soc. Bot. Fr.,' ix, p. 281. The author points out seven grades between complete absence of petals and their presence in the normal number in this plant. See also Gaudin, in 'Koch. Fl. Helv.;' Koch. 'Synops. Fl. Germ.;' Cramer, 'Bildungsabweich,' p. 85.
[466]De Rochebrune, 'Bull. Soc. Bot. Fr.,' ix, p. 281. The author points out seven grades between complete absence of petals and their presence in the normal number in this plant. See also Gaudin, in 'Koch. Fl. Helv.;' Koch. 'Synops. Fl. Germ.;' Cramer, 'Bildungsabweich,' p. 85.
[467]'Bull. Acad. Belg.,' t. xix, part 1, p. 255.
[467]'Bull. Acad. Belg.,' t. xix, part 1, p. 255.
[468]'Bull. Bot.,' i, p. 7, tab. i, f. 7.
[468]'Bull. Bot.,' i, p. 7, tab. i, f. 7.
[469]See Gay, 'Ann. Sc. Nat.,' iii, p. 27.
[469]See Gay, 'Ann. Sc. Nat.,' iii, p. 27.
[470]'Ann. Sc. Nat.,' 4 ser., v, p. 305.
[470]'Ann. Sc. Nat.,' 4 ser., v, p. 305.
[471]Cramer, 'Bildungsabweich,' p. 90.
[471]Cramer, 'Bildungsabweich,' p. 90.
[472]See also Clos, 'Bull. Soc. Bot. Fr.,' xiii, p. 96, adnot.
[472]See also Clos, 'Bull. Soc. Bot. Fr.,' xiii, p. 96, adnot.
[473]See Cramer, 'Bildungsabweich,' p. 7. Hildebrand, 'Bot. Zeit.,' xx, 1862, p. 209.
[473]See Cramer, 'Bildungsabweich,' p. 7. Hildebrand, 'Bot. Zeit.,' xx, 1862, p. 209.
[474]See Hildebrand, 'Bot. Zeit.,' xx, 1862, p. 209.
[474]See Hildebrand, 'Bot. Zeit.,' xx, 1862, p. 209.
[475]'Bull. Soc. Bot. Fr.,' viii, p. 287.
[475]'Bull. Soc. Bot. Fr.,' viii, p. 287.
[476]'Bull. Soc. Bot. Fr.,' vol. viii, 1861, p. 152.
[476]'Bull. Soc. Bot. Fr.,' vol. viii, 1861, p. 152.
[477]Ibid., ix, p. 275.
[477]Ibid., ix, p. 275.
[478]Ibid., 1861, vol. viii, p. 149.
[478]Ibid., 1861, vol. viii, p. 149.
[479]'Lobelia,' p. 55.
[479]'Lobelia,' p. 55.
[480]'Phil. Bot.,' p. 119.
[480]'Phil. Bot.,' p. 119.
[481]'Cat. Plant. Pyr,' p. 58.
[481]'Cat. Plant. Pyr,' p. 58.
[482]Moquin-Tandon, loc. cit., p. 328.
[482]Moquin-Tandon, loc. cit., p. 328.
[483]For other instances see Chatin in 'Ann. Sc. Nat.,' 4 ser., vol. v, p. 305.
[483]For other instances see Chatin in 'Ann. Sc. Nat.,' 4 ser., vol. v, p. 305.
[484]See also Morren. 'Bull. Acad. Belg.,' xv, Fuchsia, p. 67.
[484]See also Morren. 'Bull. Acad. Belg.,' xv, Fuchsia, p. 67.
[485]Cited in 'Bull. Soc. Bot., France,' t. xiv ("Rev. Bibl."), p. 253.
[485]Cited in 'Bull. Soc. Bot., France,' t. xiv ("Rev. Bibl."), p. 253.
[486]'Primit. Flor. Amurens.' p. 57.
[486]'Primit. Flor. Amurens.' p. 57.
[487]'Flora.' 1848. p. 484.
[487]'Flora.' 1848. p. 484.
In the animal kingdom the entire adult organism, as well as each of its separate parts, has certain dimensions, beyond which, under ordinary circumstances, it does not pass, either in the one direction or the other. It may not be easy or possible to state what the limits are, but, practically, this inability to frame a precise limitation is productive of no inconvenience. It is universally admitted that a certain animal attains such and such dimensions, and that one organ has a certain proportionate size as contrasted with another. The same rules hold good in the case of plants, though in them it is vastly more difficult to ascertain what may be called the normal dimensions or proportions. Nevertheless observation and experience soon show what may be termed the average size of each plant, and any disproportion between the several organs is speedily detected.
When there is a general reduction in size throughout all the organs of a plant, or throughout all the nutritive organs, stem, leaves, &c., and the several portions participate in this diminished size, we have what are generally termed "dwarf varieties," dwarf in comparison, that is, with the ordinary condition of the plants; on the other hand, if the entire plant, or, at least, if thewhole of one set of organs be increased in size beyond the recognised average, we have large varieties, often qualified by such terms asmacrophylla,longifolia,macrantha, &c. &c. In all these cases either the entire plant or whole series of organs are alike increased or diminished beyond average limits; and such variations are often very constant, and are transmitted by hereditary transmission. It may be supposed that such deviations may have originated, in the first instance, either from excessive use, or from disuse, or from the agency of certain conditions promoting or checking growth, as the case may be; but whether or no, it is certain that these variations often persist under different conditions, and that they often retain their distinctive characters side by side with plants presenting the normal average dimensions. In other cases the variations in size are of a less general character, and affect certain organs of a whorl in a relative manner, as, for instance, in the case of didynamous or tetradynamous stamens, where two or four stamens are longer than their fellows, the long or short stamens and styles of di- and tri-morphic flowers, &c. These differences are sometimes connected with the development of parts in succession, and not simultaneously.
Teratological deviations of size differ from those of which mention has just been made chiefly in this, that they are more limited in their manifestations. It is not, as a rule, the whole plant, or the whole series of nutritive or of reproductive organs, that are affected, but it is certain parts only; the alteration in size is more a relative change than an absolute one.
For convenience sake the teratological alterations of size may be divided into those which are the result ofincreased growth and those which arise from diminished action. It will be seen, therefore, that in these instances it is the bulk of the organs that is increased, not their number; moreover, their development or metamorphosis is not necessarily altered. In connection with increased size an alteration of consistence is so frequent that the two phenomena are here taken together. It will be borne in mind that the changes of consistence from membranous to succulent or woody are very frequent in the ordinary course of development. They may also occur as accidental phenomena, or the normal conditions of any particular flower or fruit may be exactly reversed, the usually succulent fruit becoming dry and capsular, and so forth.
The term hypertrophy may serve as a general one to comprise all the instances of excessive growth and increased size of organs, whether the increase be general or in one direction merely. General hypertrophy is more a variation than a deformity, unless indeed it be caused by insect puncture or the presence of a fungus, in which case the excessive size results from a diseased condition. For our present purpose hypertrophy may be considered as it affects the axile or the foliar organs, and also according to the way in which the increased size is manifested, as by increased thickness or swelling—intumescence, or by augmented length-elongation, by expansion or flattening, or, lastly, by the formation of excrescences or outgrowths, which may be classed under the head of luxuriance or enation.
As size must be considered in this place relatively, it is not possible to lay down any precise line separating what are considered to be the normal dimensions from those which are abnormal.
In practice no inconvenience will be found to accrue from this inability to establish a fixed rule, and we may say that an hypertrophied organ is one which, from some cause or other, attains dimensions which are not habitual to the plant in its usual, healthy, well-formed state.
It will be seen that under this general head of hypertrophy, increase of size, however brought about, is included; thus, not only increase in length, but also in thickness; alterations of substance or consistence, no less than of dimensions, are here grouped together.The alterations of consistence resulting from an inordinate development of cellular, fibrous, or ligneous tissue, are, of course, strictly homologous with the similar changes which occur, under ordinary circumstances, during the ripening of fruits or otherwise.
Hypertrophy, whatever form it may assume, may be so slight as not perceptibly to interfere with the functions of the part affected, or it may exist to such an extent as to impair the due exercise of its office. It may affect any or all parts of the plant, and is generally coexistent with, if not actually dependent on, some other malformation. Thus, the inordinate growth of some parts is most generally attended by deficiency in the size and number of others, as in the peripheral florets ofViburnumorHydrangea, where the corollas are relatively very large, and the stamens and pistils abortive.
A swollen or thickened condition (renflement) is usually the result of a disproportionate formation of the cellular tissue as contrasted with the woody framework of the plant. We see marked instances of it in cultivated carrots and turnips, the normal condition of the roots or root-stocks in these plants being one of considerable hardness and toughness, and their form slender, tapering, and more or less branched.
The disproportionate development of cellular tissue is also seen in tubers and bulbs, and in the swollen stems of such plants asEchinocactus,Adenium obesum, some species ofVitis, &c. So, too, the upper portion of the flower-stalk occasionally becomes much dilated,so as ultimately to form a portion of the fruit. But it is not necessary to give farther illustrations of this common tendency in some organs to become hypertrophied. As a result of injury from insects or fungi, galls and excrescences of various kinds are very common, but their consideration lies beyond the scope of the present work.
Fig.200.—Pelargonium, one branch of which was hypertrophied.
Fig.200.—Pelargonium, one branch of which was hypertrophied.
Enlargement of axile organs.—All the species ofPelargonium,Geranium,Mirabilis,as well as those ofCaryophylleæand other orders, have tumid nodes as a normal occurrence. In the genusPelargoniumthis swelling is sometimes not confined to the nodes, butextends to the interspaces between them,e.g.P. spinosum. This condition, which happens as a natural feature in the species just named, may also occur as an exceptional thing in others. The author is indebted to Dr. Sankey for a branch ofPelargoniumwhich was thus thickened, the remaining branches not being in any way affected. The leaves on the swollen branch were smaller than the others, and their stalks more flattened. There was, in this instance, no trace of fungus or insect to account for the swelling of a single branch, which might, therefore, be due to bud-variation, perhaps to reversion to some ancestral form. The repeated cross fertilisations to which Pelargoniums have been subjected render this hypothesis not an improbable one.
As an accompaniment to a spiral torsion of the woody fibres, this distension of the stem is frequently met with, as inValeriana,Dipsacus,&c. (See Spiral Torsion.)
Knaurs.—On certain trees, such as the oak, the hornbeam, some species ofCratægus, &c., hard woody lumps may occasionally be seen projecting, varying greatly in size, from that of a pea to that of a cocoa-nut. They are covered with bark, and consist in the interior of very hard layers of wood disposed irregularly, so as to form objects of beauty for cabinet-makers' purposes. From the frequent presence of small atrophied leaf-buds on their surface, it would seem as if the structures in question were shortened branches, in which the woody layers had become inordinately developed, as if by compensation for the curtailment in length.[488]The cause of their formation is not known, but it has been ascertained that they are not due to insect agency. Knaurs may occasionally be used for purposes of propagation, as in the case ofthe "uovoli of the olive" and the "burrs" that are formed on some varieties of apple, from which both roots and leaf-shoots are produced in abundance.
A distinction must be drawn between those instances in which the swelling is solid throughout from the excessive formation of cellular tissue, and those wherein it is hollow from the more rapid growth of the outer as contrasted with the inner portions. These latter cases might be classed under the head of distension.
Fig.201.—Formation of tubers or hypertrophied buds in the axils of leaves in the potato.
Fig.201.—Formation of tubers or hypertrophied buds in the axils of leaves in the potato.
Enlargement of the budsmay be seen in the case of bulbs and tubers. Occasionally these organs are developed in the axils of leaves, when their naturebecomes apparent. A swollen bud or bulbil in this situation is not uncommon in some cultivated tulips and lilies. The presence of small tubers in the axils of the leaves in the potato, as shown in fig. 201, is also not unfrequent.
Fig.202.—Inflorescence of ash (Fraxinus), with hypertrophied pedicels, flowers absent.
Fig.202.—Inflorescence of ash (Fraxinus), with hypertrophied pedicels, flowers absent.
Enlargement of the flower-stalk.—The cauliflower and broccoli afford familiar illustrations of hypertrophy of the flower-stalk, accompanied by a correspondingdefective development of the flowers. In the case of the ash the terminal pedicels occasionally become swollen and distorted, while the flowers are completely deficient, as shown in the adjacent cut (fig. 202).
In grapes a similar condition may occasionally be met with in which the terminal pedicels become greatly swollen and fused into a solid mass. It would seem probable that this change is due to insect puncture, or to the effect of fungus growth at an early stage of development, but as to this point there is at present no evidence.[489]
Fig.203.—Monstrous pear, showing extension and ramification of the succulent floral axis. The bases of the sepals are also succulent.
Fig.203.—Monstrous pear, showing extension and ramification of the succulent floral axis. The bases of the sepals are also succulent.
In the apple a dilatation of the flower-stalk below the ordinary fruit may occasionally be observed, thus giving rise to the appearance of two fruits superposed and separated one from the other by a constriction.(See fig. 176, p. 327.) The lower swelling is entirely axial in these cases, as no trace of carpels is to be seen. M. Carrière[490]mentions an instance wherein from the base of one apple projected a second smaller one, destitute of carpels, but surmounted by calyx-lobes as usual. The direction of this supernumerary apple was the exact opposite of that of the primary fruit.
Fig.204.—Monstrous pear, showing extension and swelling of axis, &c.
Fig.204.—Monstrous pear, showing extension and swelling of axis, &c.
In pears, quinces, and apples, a not uncommon deviation is one in which the axis is prolonged beyond the ordinary fruit, like which it is much swollen. Occasionally the axis is not only prolonged, but even ramifies, the branches partaking of the succulent character of the ordinary pome. Such instances are frequently classed under the head of prolification, but they have in general no claim to be considered in this light, for the reasons already given in the chapter relating to that subject. (See p. 135.)[491]
A very curious illustration of hypertrophy of the flower-stalk is recorded and figured by M. Carrière[492]in the cherry. The calyx in these fruits was completely superior, the succulent portion of the fruit being made up of the dilated extremity of the peduncle, and possibly in part of the base of the calyx. The general appearance was thus that of a crab-apple. There was no stone in the interior, but simply a rudimentary kernel or seed.[493]
Moquin-Tandon records an instance in which the stamens of each individual flower in the inflorescence of a vine were hypertrophied, the sepals, petals, and other organs of the flower, being proportionately diminished.[494]
In this place may also be mentioned the hypertrophied condition of the placenta observed by Alphonse de Candolle in a species ofSolanum, and also in a species ofMelastoma. Not only was the placenta unusually large in these flowers, but it also protruded beyond the ovary.[495]A similar state of things inLobeliaandCupheahas already been alluded to under the head of Alterations of Direction (p. 210).
The following singular growth in a tomato is describedby the Rev. M. J. Berkeley in the 'Gardeners' Chronicle' for 1866, p. 1217, and appears to have been an extension of the placenta:—"On the first glance it seemed as if an unusually large grape-stone had accidentally fallen on the upper surface of the fruit, and was attached by the narrow base. The process was, however, five lines long, and much narrowed below, besides which, though it was pale green above, the base was coral-red, like the tomato itself. It grew on a narrow and shallow crack on the surface of the fruit, and was found below to communicate directly with a fibro-vascular bundle, which entered into the composition of a portion of the placenta. On making a vertical section, instead of being succulent, as I expected, it was white and spongy within, with several lacunae, and one or two irregular fibro-vascular bundles, with highly developed spiral vessels threading the centre. These vessels, moreover, were tinged with brown, as in many cases of diseased tissues. There was not the slightest appearance of placentæ or anything indicating an abortive fruit. On closer examination the cuticle was found to consist of thick-walled cells, exactly like those of the tomato, while the spongy mass consisted of a similar tissue to the fleshy portion of the fruit, but with far less wrinkled walls, and more indistinct intercellular spaces. The most striking point, however, was the immense quantity of very irregular and unequal starch-grains with which they were gorged, which gave a peculiar sparkling appearance to them when seenen masse. I am inclined to regard the body rather as an abortive axis than an undeveloped fruit. In almost all, if not all, these cases of abnormal growth, whether from leaves, petioles, fruit, or other portions of the plant, we find an immediate connection with one or more spiral vessels, which if not existent at first are developed sooner or later. In the present case the connection of the fibro-vascular tissue of the fruit and abnormal growth was plain enough, but whether it existed when the body wasfirst given off I am unable to say, as it was fully developed when the fruit was brought to me."
Enlargement of the leaves.—Increase in the size or substance of leaves takes places in several ways, and affects the whole or only certain portions of them. The simplest form of this malformation is met with in our cabbages, which, by the art of the gardener, have been made to produce leaves of greater size and thickness than those which are developed in the wild form. In such instances the whole substance of the leaf is increased in bulk, and the increase affects the fibrous framework of the leaves as well as the cellular portions, though the exaggerated development of the latter is out of proportion to that of the former.
In some species ofPodocarpusthere may occasionally be seen at the base of the branchlets a dozen or more fleshy scales, of a rose colour, passing gradually into the ordinary leaves of the plant, and evidently analogous to the three fleshy confluent bracts which surround the ripe fruit.
In other instances, while the fibrous framework of the leaf retains its usual degree of development, the cellular parenchyma is developed in excess, and, if the increase is so arranged that the number of superposed layers of the cellular tissue is not increased, or their thickness exaggerated, then we get such leaves as those of the "kail," or of the "Savoys" leaves, which are technically called by descriptive botanists "folia bullata." In such leaves the disc of the leaf, rather than the margin, is increased and its surface is thrown up into little conical projections, which are hollow on the under side.
But leaves may increase beyond their usual size without such grave alterations of form as those to which allusion has just been made. It is well known that if a tree be cut down and new shoots be sent out from the stump, the leaves formed on these shoots very often greatly exceed the ordinary ones in dimensions.Such cases as this hardly come under the head of malformations. But where one part only of the leaf is excessively developed, the other portion remaining in its ordinary condition, there can be no hesitation in ranking the phenomenon as teratological.
Thus, Moquin says that the median nerve may be prolonged beyond the blade of the leaf in the form of a short strap or ribbon-like excrescence, while, at other times, the lateral parts of the leaf are subjected to undue development. He refers to a case cited by Schlotterbec[496]in which each side of the leaves of a yellow "violier" (wallflower) was dilated into a kind of projecting lobe on either side of the true apex of the leaf, thus rendering it in appearance three-lobed. M. Delavaud[497]puts on record a case of hypertrophy in the leaves of the common elm, resulting in the formation of an additional lobe and a return to the tricostate type. A leaf so affected is stated to have presented the appearance of a fusion of two leaves. (See also Multiplication of leaves, p. 353.)
The hypertrophied and coloured leaf ofGesneraoccupying the place of the absent inflorescence has been previously alluded to under the head of displacement (p. 88).
In some instances hypertrophy is the opposite of suppression; as in the case previously mentioned, where the stipule in the inflorescence of a pea, which is usually undeveloped and rudimentary, was developed in the form of a leafy cup or pitcher.
Another instance of the development of parts usually suppressed, is afforded by the bud-scales ofMagnolia fuscata, which may sometimes be found with small but perfect leaves projecting from them, the leaf in this case being the lamina which is ordinarily abortive, while the scales are the representatives of the stipules. This condition is said by Hooker and Thomson ('Flora Indica,' p. 73) to be constant inMagnolia Campbelli.
Enlargement of the perianth, &c.—One or all the segments of the perianth may be subjected to hypertrophy; thus, the utricle ofCarex vulpinamay frequently be observed to attain four or five times its usual size, the contained ovary remaining unaffected. This condition is generally the result of insect puncture. The growth of parasitic fungi will produce a similar result, as is often seen in the common shepherd's purse,Thlaspi bursa pastoris, and otherCruciferæ. The perianth ofRumex aquaticushas been also observed to be occasionally hypertrophied in conjunction with a similar condition of the pistil and with atrophy of the ovules.
Moquin relates having found flowers ofSalsola Kaliand ofChenopodium muralein which some of the segments of the perianth were five or six times larger than they should be.