FOOTNOTES:

Fig.205.—Hypertrophy of the perianth inCocos nucifera.

The adjoining woodcut represents a singular condition of some cocoa-nuts in the Kew Museum, theappearance of which is due apparently to an hypertrophied condition of the segments of the perianth, which have not only increased in length as the central nut has ripened, but have developed in their tissues that fibrous tissue which ordinarily is found in the pericarp only. This view of the structure of these nuts is borne out by the fact that, under normal circumstances, the base of the perianth contains a considerable amount of fibrous material. In the present case this has increased to such an extent that the fruit appears surrounded by a double husk, by an inner one as usual, and by an outer six-parted one.

It will be remembered that in some of theCinchonaceæ, e.g.Mussænda,Pinckneya,Calycophyllum, one or more of the calycine lobes are normally dilated and petaloid, the others remaining small and comparatively inconspicuous. Inequality in size is, indeed, a common occurrence in the sepals of many natural orders—Polygalaceæ,Leguminosæ,Labiatæ, &c. The flowers of a rose are mentioned by Moquin as having presented an enlargement of the calyx without any other alterations in form. Schlechtendal has noticed the same thing inPapaver Rhœas, Reichenbach inCampanula persicifolia, and A. de Candolle inC. Rapunculus. M. Brongniart also has recorded[498]a remarkable variety ofPrimula sinensiscultivated in the Jardin des Plantes at Paris, wherein the calyx is enormously developed. MM. Fournier and Bonnet have described flowers ofRubuswith hypertrophied calyx in conjunction with atrophy and virescence of the petals and other changes.[499]

The corolla may be hypertrophied in some cases, though the change is more rare than in most other organs. Moquin-Tandon mentions as subject to this anomaly species ofGaleopsis,Prunella,Scabiosa, andDipsacus, and also mentions a remarkable variety ofViola odoratacultivated in the neighbourhood ofToulouse. The same learned author also alludes to the so-called double Composites, viz. those in which the usually tubular florets of the disc assume the form and proportions of those of the ray, but these are hardly cases of hypertrophy.

Enlargement of the andrœcium.—Dunal[500]alludes to a curious instance in a species ofVerbascum, the lower flowers of which had hairy stamens as usual, but the filaments of the topmost flower were quite destitute of hairs, and dilated like a flat ribbon.

Moquin relates having found in the neighbourhood of Toulouse a plant ofSolanum Dulcamarain which all the upper flowers had two or three stamens of larger dimensions than the others. This happens habitually inSolanum tridynamumandS. Amazonicum, and to a less extent inS. vespertilioandS. cornutum; also in some species ofHyoscyamus. These cases show the close affinity between theSolanaceæand theScrophulariaceæ.

Enlargement of the gynœcium.—In some flowers which have become accidentally female the pistil becomes unusually large, and even to such an extent as to prevent the passage of the pollen. Moquin remarks having seen this enlargement in the pistils ofSuæda fruticosaandKochia scoparia. The flowers of these Chenopods, under these circumstances, resemble the female flowers of some nettles. The styles ofAnemoneare also much enlarged as the result of cultivation, and from their petaloid appearance resemble those of theIris(Goethe). MM. Seringe and Heyland[501]have figured some anomalous flowers ofDiplotaxis tenuifoliain which the pistil, more or less distended and deformed, was considerably elongated below, so that it seemed to be borne upon a long stalk, analogous to that of fruits of Capparids. Dr. Klinsman[502]mentions an instance of a similar kind combinedwith hypertrophy of the sepals and pistils; indeed, the alteration is not uncommon among Crucifers.Pyrethrum inodorumis very subject to hypertrophy. The styles of its radial florets become elongated without any other alteration; at the same time the small corollas become green, and show a tendency to assume a foliaceous condition. Sometimes the hypertrophy affects also the styles of the central florets, and these also become enlarged to double or treble their usual dimensions.

Linné has remarked that the ovary ofTragopogonsometimes assumes very large dimensions, as also does the pappus. He mentions a double-flowered variety, the ovaries of which become ten or twelve times larger than ordinary. M. Clos[503]records an instance inRumex scutatuswherein the pistil was hypertrophied or club-shaped, and open at the top, or in other cases funnel-shaped, three-lobed at the summit, each lobe terminated by a style. One of the most frequent causes tending to the hypertrophy of the pistil is attributable to the puncture of insects; thus, when the ovary ofJuncus articulatusis thus punctured, it acquires a size two or three times larger than ordinary, becoming at the same time sterile.[504]

Occasionally the enlargement may be due to a fusion or incorporation of other elements; thus, M. Lemaire describes an instance in which the style ofSinningia purpureawas much larger than ordinary, tubular, bearing three small lobes, and altogether bearing much resemblance to the column or "gynosteme" of Orchids. This appearance was due to the cohesion and intimate union of the styles with three abortive stamens.[505]

Enlargement of the fruit.—Most cultivated fruits are in a state of true hypertrophy. Girod de Chantrans, after many trials, succeeded in producing a peculiar varietyof pea with pods double the ordinary size.[506]M. Clos[507]mentions a case wherein the carpels ofDelphinium dictyocarpumwere hypertrophied. The change in size may or may not be attended by a difference in form; thus, in certainLeguminosæ, asMedicago lupulina,Melilotus leucantha, the carpels are sometimes hypertrophied and elongated, so as to resemble a claw or hook.[508]

The fruit of the common groundsel (Senecio vulgaris) is in its normal condition two or three times shorter than the involucre, and cylindrical for its whole length, but it frequently happens that the fruits become as long as the involucre itself, and taper from the base upwards, so as to become beaked. Under this head may also be mentioned the fleshy bulbils that are found in the capsules ofCrinum,Amaryllis, andAgave. These are true seeds enormously dilated.[509]In these seeds the outer coating becomes very thick and fleshy, and is traversed by spiral vessels.

It is obvious that very important results in a practical point of view may be and have been arrived at by cultivators availing themselves of this tendency of plants to increase in dimensions under certain circumstances. It is needless to do more than refer to the many fruits, vegetables, and cereals, which have thus become enlarged and improved by careful selection and rearing.

Alterations of consistenceoften accompany changes in size. The change may be one whereby the tissues become unusually hardened, by the excessive formation of secondary woody deposits, or softer and more succulent than ordinary, from the formation of an inordinate amount of loose cellular tissue. Generallyspeaking, the appearances presented in such cases are not sufficiently striking to demand notice other than as regards their size. One illustration, however, may be cited from its singularity. This was the case of a dahlia, in which the centre of the flower was occupied by a projecting knob as large as a walnut, brown in colour, and very hard in texture. This knob was nothing but the enlarged and indurated extremity of the common receptacle, destitute of the scales and florets which usually spring from it. No insect-puncture could be detected, and no other reason for this peculiarity could be ascertained.

FOOTNOTES:[488]On the subject of knaurs, the reader is referred to Trécul, 'Ann. Sc. Nat.,' 3 ser., vol. xx, p. 65; Lindley, 'Theory of Horticulture;' Rev. M. J. Berkeley, 'Gardeners' Chronicle,' 1855, p. 756.[489]Jaeger, 'Flora.' 1860. p. 49, tab. i.[490]'Revue Horticole,' 1868, p. 110, figs. 12, 13.[491]The reader may also refer for further information on the subject of malformed pears to Irmisch. 'Flora,' 1858, p. 38, tab. i; Lindley, 'Theory of Horticulture'; Caspary, 'Bull. Soc. Bot. France,' vol. vi, 1859 (Rev. Bibl.), p. 235; Duhamel, 'Phys. Arbr.,' liv. iii, cap. 3. p. 393, fig. 308; Bonnet, 'Recherch. Us. feuilles,' tab. xxvi, fig. 2; Moquin-Tandon, 'El. Ter. Veg.,' p. 384, &c. Some of the cases recorded are, however, instances of true prolification.[492]'Revue Horticole' 1868, p. 310.[493]The interest of this accident is great, as showing how an habitually superior ovary may become inferior—a change so rare in its occurrence that its existence has been denied, and thus forming a marked contrast with the frequency with which the converse change of an inferior ovary to a superior one, from want of union with the calyx or from imperfect development of the peduncle, may be observed. It is also interesting as showing how the peduncle may become swollen, and at the same time how the woody deposit of the endocarp may, as if by compensation, be deficient. And, again, the malformation is not without significance in regard to the relationship between the drupaceous and the pomaceous subdivisions ofRosaceæ. The case would fitly be included under alterations of position, but the sheets relating to that subject were printed off before the publication of M. Carrière's notice.[494]'Bull. Soc. Bot. France,' 1860, vol. vii, p. 881.[495]"Monstr. Veget.," in 'Neue Denkschrift.'[496]"Sched. de Monst. Plant." in 'Act. Helvet.,' t. ii, pl. ii, f. 14.[497]'Bull. Soc. Bot. France,' vol. viii, 1861, p. 144.[498]'Ann. Sc. Nat.,' sér. 2, t. i, p. 308, pl. ixc, fig. 1.[499]'Bull. Soc. Bot. France,' 1862, t. ix, p. 37.[500]'Consid. org. Fleur.,' Montpell., 1829, 25, 26, pl. ii, f. 18 and 19.[501]'Bull. Bot.,' t. i, p. 7, tab. 1.[502]'Linnæa,' vol. x, p. 604, tab. 5.[503]'Mém. Acad. Sc. Toulouse,' 5 ser., vol. iii.[504]'Ré. nosol. Végét.,' pp. 342.[505]'Illustr. Hortic.,' 1868, Misc., p. 62.[506]'Ann. Soc. Linn.,' Paris, t. i, p. 139.[507]'Mém. Acad. Toulouse,' t. 6, 1862.[508]'D. C. Prod.,' ii, pp. 172, 187.[509]Richard, "Obs. sur les bulbilles des Crinum;" 'Ann. Sc. Nat.,' t. ii, p. 12. pl. i, fig. 1, 2. See also A. Braun, "Mémoire sur les graines charnues des Amaryllidèes," &c.; 'Ann. Sc. Nat.,' 1860, vol. xiv, p. 1, tab. 1.

[488]On the subject of knaurs, the reader is referred to Trécul, 'Ann. Sc. Nat.,' 3 ser., vol. xx, p. 65; Lindley, 'Theory of Horticulture;' Rev. M. J. Berkeley, 'Gardeners' Chronicle,' 1855, p. 756.

[489]Jaeger, 'Flora.' 1860. p. 49, tab. i.

[490]'Revue Horticole,' 1868, p. 110, figs. 12, 13.

[491]The reader may also refer for further information on the subject of malformed pears to Irmisch. 'Flora,' 1858, p. 38, tab. i; Lindley, 'Theory of Horticulture'; Caspary, 'Bull. Soc. Bot. France,' vol. vi, 1859 (Rev. Bibl.), p. 235; Duhamel, 'Phys. Arbr.,' liv. iii, cap. 3. p. 393, fig. 308; Bonnet, 'Recherch. Us. feuilles,' tab. xxvi, fig. 2; Moquin-Tandon, 'El. Ter. Veg.,' p. 384, &c. Some of the cases recorded are, however, instances of true prolification.

[492]'Revue Horticole' 1868, p. 310.

[493]The interest of this accident is great, as showing how an habitually superior ovary may become inferior—a change so rare in its occurrence that its existence has been denied, and thus forming a marked contrast with the frequency with which the converse change of an inferior ovary to a superior one, from want of union with the calyx or from imperfect development of the peduncle, may be observed. It is also interesting as showing how the peduncle may become swollen, and at the same time how the woody deposit of the endocarp may, as if by compensation, be deficient. And, again, the malformation is not without significance in regard to the relationship between the drupaceous and the pomaceous subdivisions ofRosaceæ. The case would fitly be included under alterations of position, but the sheets relating to that subject were printed off before the publication of M. Carrière's notice.

[494]'Bull. Soc. Bot. France,' 1860, vol. vii, p. 881.

[495]"Monstr. Veget.," in 'Neue Denkschrift.'

[496]"Sched. de Monst. Plant." in 'Act. Helvet.,' t. ii, pl. ii, f. 14.

[497]'Bull. Soc. Bot. France,' vol. viii, 1861, p. 144.

[498]'Ann. Sc. Nat.,' sér. 2, t. i, p. 308, pl. ixc, fig. 1.

[499]'Bull. Soc. Bot. France,' 1862, t. ix, p. 37.

[500]'Consid. org. Fleur.,' Montpell., 1829, 25, 26, pl. ii, f. 18 and 19.

[501]'Bull. Bot.,' t. i, p. 7, tab. 1.

[502]'Linnæa,' vol. x, p. 604, tab. 5.

[503]'Mém. Acad. Sc. Toulouse,' 5 ser., vol. iii.

[504]'Ré. nosol. Végét.,' pp. 342.

[505]'Illustr. Hortic.,' 1868, Misc., p. 62.

[506]'Ann. Soc. Linn.,' Paris, t. i, p. 139.

[507]'Mém. Acad. Toulouse,' t. 6, 1862.

[508]'D. C. Prod.,' ii, pp. 172, 187.

[509]Richard, "Obs. sur les bulbilles des Crinum;" 'Ann. Sc. Nat.,' t. ii, p. 12. pl. i, fig. 1, 2. See also A. Braun, "Mémoire sur les graines charnues des Amaryllidèes," &c.; 'Ann. Sc. Nat.,' 1860, vol. xiv, p. 1, tab. 1.

The class of cases coming under this head are sufficiently indicated by the name. There are many instances of this phenomenon occurring under different conditions, which, though unusual, can hardly be called abnormal, such, for instance, as the great lengthening of roots in their search for water, the excessive elongation that takes place in plants when grown at a distance from the light, in their endeavour to attain to which they become, as gardeners phrase it, "drawn." A similar result is brought about in forests or plantations, where long spars are required, by allowing the trees to grow very close to each other, so as to prevent the lateral extension of the branches. When plants grow in running water their roots, stems, and sometimes their leaves, become excessively elongated, as inRanunculus fluitans, the flower-stalks ofValisneria spiralis, &c. These are cases of variation rather than of malformation, but are none the less curious, or sometimes perplexing; thus, Lapeyrouse described, inhis 'Supplement à la flore des Pyrenées,' p. 27, under the namePotamogeton bifolium, a plant which Mr. Bentham subsequently discovered to be nothing but a flowerless variety ofVicia Fabadistorted by its growth in water.[510]

Elongation of the root.—This, as already remarked, is more often a variation than a malformation, and is usually due to the presence of water at a distance necessitating growth at the extremities of the root, or to the presence of some obstacle, such as a stone, to avoid which the root elongates till it has passed the obstruction. Occasionally in Crocus corms some of the fibrils may be met with much lengthened and thickened, and invested with a fleshy sheath. It is not certain, however, that these structures are roots; possibly, nay probably, they may be processes from the stem thrust downwards into the soil, similar to the formations already described in the tulip (p. 85, fig. 39).

Elongation of the inflorescence.—Under this heading it is necessary to consider lengthening of the common rachis in the case of an aggregate inflorescence, and lengthening of the individual flower-stalks, whether they be solitary or portions of a multiple inflorescence. The two phenomena may occur together, but they are quite as often independent one of the other. Thus, amongUmbelliferæthe umbels are occasionally met with supported on unusually long stalks, while the pedicels of the individual flowers may or not be increased in length; so also with some of the Composites, or the heads of flowers of someLeguminosæ,Trifolium repens, &c. &c.

Another illustration of the sort is that recorded by M. Fournier, wherein the usually umbellate inflorescence ofPelargoniumwas, through the lengthening of the main stalk, transformed into a raceme. Among Composites a similar change may sometimes be met with.

MM. Clos and De Schönefeld have recorded the existence of a variety of the sweet chestnut (Castanea)in which the female catkins were as long, and bore nearly as many flowers, as the male spikes. This is stated to be of constant occurrence in some localities, and to be accompanied by a diminished size of the fruits. A similar elongation has been observed in the case of the walnut, catkins of which have been seen bearing thirty to thirty-five large nuts.[511]

In the strobile of the hop,Humulus Lupulus, a like elongation may sometimes be met with, generally in association with a more or less leafy condition of some of the scales.

Of a similar character, but complicated with extrusion or eversion of an ordinarily concave axis, is the fig described by Zuccarini,[512]and from the appearances presented by which that author draws the inference that the peculiar appearance of the fig is due to the formation of a large number of small bracts blended together for the greater part of their length, and accompanied by the suppression of the internodes, and consequent shortening of the axis. In the monstrous fruit the axis is prolonged, and forms a kind of raceme or catkin, surrounded at the base by numerous bracts, as in manyAmentaceæ. (See p. 204, figs. 105, 106.)

A lengthening of the axis of the female strobiles ofConiferæis not of infrequent occurrence inCryptomeria japonica,Larie europæa, &c., and this is usually associated, as has been before stated, with a leaf-like condition of the bracts, and sometimes even with the development of leaf-bearing shoots in place of the scales. (See under Prolification of Inflorescence and Phyllomorphy, and for references, p. 115.)

Elongation of the secondary flower-stalks.—In the previous section the effect of elongation of the main rachis has been considered. A corresponding deviation occurs inthe peduncles or pedicels, and sometimes alters the general character of the inflorescence very considerably, converting a spike into a raceme, a raceme into a corymb, a capitulum into an umbel, and so forth. A few such cases may here be alluded to. Fig. 206 represents a specimen ofRanunculus acris, in which the lower and lateral flower-stalks were not only increased in number, but so much lengthened as to form a flat-topped inflorescence—a corymbose cyme. In many leguminous plants, as inTrifolium repens,Lotus corniculatus, &c., what is usually a compact spike, or headof flowers, becomes a raceme from the elongation of the pedicels. InUmbelliferæa similar change occurs, by virtue of which sometimes the umbels themselves, and at other times the florets, are raised on unusually long stalks, as inAngelica Razoulzii,Carum Carui,Thysselinum palustre.[513]InCompositæ, when affected by an analogous change, the capitulum assumes the appearance of a simple umbel, as inHypochæris radicata,Senecio vulgaris, and other plants.

Fig.206.—Inflorescence ofRanunculus acris, with secondary peduncles lengthened.

In some of the double-flowered apples which have been previously alluded to, the flower-stalk is inordinately long when compared with the adjacent ones. Possibly in some of these cases the absence of the usual swelling of the upper part of the peduncle may be connected with its increased length. One of the most striking instances of lengthened flower-stalk occurred in an apple flower, wherein there was no swelling beneath the calyx, while the latter was represented by five perfect stalked leaves.

Elongation of the leaves.—In the case of water plants this change keeps pace with the corresponding growth of the stem,e.g.Ranunculus fluitans, and in terrestrial plants there are varieties termed longifoliar, from the unusual length of the leaves. A similar lengthening occurs in the involucral leaves ofUmbelliferæandCompositæ, changing very materially the general aspect of the inflorescence. Occasionally, also, the leaf-lobes of parsley (Apium Petroselinum) and other crested-leaved plants may be observed to lose their ordinary wavy form, and to be lengthened into flat riband-like segments, as shown in fig. 207.

The only further illustrations that it is requisite to give of such changes in this place are those occurring in lobed or compounded leaves, which, from a lengthening of the midrib or central stalk, convert a digitate or palmate leaf into a pinnate one. In these instancesthe lobes or leaflets become separated one from another by a kind of apostasis. This change may be frequently seen in the horse-chestnut, particularly in the young shoots formed after the trees have been pruned or pollarded. In the adjoining cut the intermediate stages between a palmate or digitate leaf to a pinnate one may be seen. The specimens from which the drawing was made were taken from the same tree at the same time.

Fig.207.—Portion of leaf of parsley, showing the change from short wavy to long flat leaf-lobes.

In the white clover,Trifolium repens, a similar transition may often be observed, as also in some species ofPotentilla.[514]

Elongation of the parts of the flower.—The only circumstance that needs especial mention under this section is the great lengthening that sometimes takes place inthe carpels, sometimes as a result of injury from insects or fungus, at other times without assignable cause.

Fig.208.—Leaves of horse-chestnut,Æsculus, showing passage from digitate to pinnate leaves.

In the case of inferior ovaries this lengthening is, perhaps, even more common, as inUmbelliferæ,Compositæ, &c. The common groundsel (Senecio vulgaris) is especially liable to this form of enlargement of thepistil, either in association with a leafy condition of the pappus or without any such change.

Elongation of the thalamus, placenta, &c.—In some plants, as inMagnoliaorMyosurus, the thalamus becomes much elongated, and bears the carpels disposed spirally around it. A similar lengthening occurs in malformed flowers, usually in association with a similar change in the lower or outer part of the flower, by virtue of which the whorls become separated from each other (Apostasis). Elongation and protrusion of the placenta have been already alluded to at p. 119, and also at p. 125. In some of these cases the elongated placenta has taken the form of a leaf-bearing shoot.[515]

Apostasis.—Engelmann made use of this term to express the separation of parts one from another by the unusual elongation of the internodes.[516]He drew a distinction between the separation of individual organs one from the other, and the corresponding displacement of whorls. The subject has already been, to a considerable degree, treated of in these pages under the head of dialysis, displacement, and prolification, and but little need here be added. With reference to the distance between one whorl and another, it will be remembered that, although in the majority of cases the floral whorls are packed closely together, yet in other instances the floral axis becomes elongated, and thus separates the whorls one from another, by structures such as the gynophores, androphores, &c., ofPassifloreæ,Caryophylleæ,Capparideæ, &c. &c.

A similar elongation of the thalamus, bringing about the separation of the floral whorls, or of their constituent parts, is very commonly met with in association with median prolification. Where the individual floral elements are thus thrown out of their usual verticillate arrangement, they naturally assume a spiral disposition,and are, in some cases, united by their margins, so that a spiral sheet or tube is formed, surrounding the axis. This frequently occurs in double flowers of the Chinese primrose,Primula sinensis.

Engelmann[517]figures a case wherein the calyx ofAnagallis phœniceawas separated by a rather long internode from the corolla, and a like illustration inTorilis Anthriscus.

Fig.209.—Flower ofDelphinium, showing apostasis of carpels, from lengthening of the thalamus, &c. (Cramer.)

A frequent change in Crucifers is due to the formation of a long stalk bearing the pod, and thus giving rise to the appearance met as a constant occurrence in Capparids.

InTropæolum majusa similar elevation of the pistil may occasionally be seen.

The adjacent figure of a monstrousDelphiniumtaken from Cramer illustrates well the elongation of the floral axis and the apostasis of the carpels. In this instance the axis is terminated by a second flower (median prolification).

One of the best-marked illustrations of these changes occurs in a permanent malformation ofEpilobium hirsutum, specimens of which were originally obtained from the late Professor Henslow. The several floral parts are here, some virescent, others truly foliaceous, and each whorl is separated from its neighbour by a rather long internode. InFuchsiaandCampanulaa like change may occasionally be observed.

Engelmann, in addition to those previously mentioned, cites the following plants as having manifested this change:

*Convallaria majalis!,*Tulipa Gesneriana!,Veronica Chamædrys,Orobanche gracilis,Solanum Lycopersicum,Gentiana campestris,Hypericum,Helleborus fetidus,Caltha palustris,Brassica oleracea!and manyRosaceæ,Caryophylleæ,Cruciferæ, andRanunculaceæ. (See Dialysis, Median Prolification, &c.)

Apostasis of the sub-floral or involucral leaves is not of infrequent occurrence in malformations affectingCompositæandUmbelliferæ. In the following genera it has been observed with especial frequency:—Torilis Anthriscus,Eryngium,Athamanta Cervaria,Leontodon,Tragopogon pratense!,Wedelia perfoliata!In garden anemones, also, it is a common deviation.

FOOTNOTES:[510]'Cat. Plant.,' Lang., p. 113.[511]'Bull. Soc. Bot. France,' t. i, 1854, p. 173, and t. xiii, p. 96.[512]'Abhandl. Math. Phys. Class.,' Band. iv, Abhandl. i, tab. i.[513]See Cramer, 'Bildungsabweich,' pp. 62–79, and Fleischer, 'Missbild, der Culturpflanzen.'[514]Schlechtendal, 'Bot. Zeit.,' 1844, p. 457; 'Linnæa,' xi, p. 301, xiv, p. 363; 'Bot. Zeit.,' 1856, p. 72; Masters, 'Rep. Brit. Assoc.,' Manchester, 1861; Coultas, 'What may be learnt from a tree,' p. 118.[515]For further details refer to the chapter on Displacements, p. 86.[516]'De Antholysi,' p. 42, § 49.[517]Loc. cit., tab. 2, f. 6.

[510]'Cat. Plant.,' Lang., p. 113.

[511]'Bull. Soc. Bot. France,' t. i, 1854, p. 173, and t. xiii, p. 96.

[512]'Abhandl. Math. Phys. Class.,' Band. iv, Abhandl. i, tab. i.

[513]See Cramer, 'Bildungsabweich,' pp. 62–79, and Fleischer, 'Missbild, der Culturpflanzen.'

[514]Schlechtendal, 'Bot. Zeit.,' 1844, p. 457; 'Linnæa,' xi, p. 301, xiv, p. 363; 'Bot. Zeit.,' 1856, p. 72; Masters, 'Rep. Brit. Assoc.,' Manchester, 1861; Coultas, 'What may be learnt from a tree,' p. 118.

[515]For further details refer to the chapter on Displacements, p. 86.

[516]'De Antholysi,' p. 42, § 49.

[517]Loc. cit., tab. 2, f. 6.

Under the above heading are included certain forms arising from excess not of growth, but of development, and consisting in the formation of supplementary lobes or excrescences from various organs.

The new formations are not due either to a repetition or to a partition of any organ, but are out-growths from others previously formed.

In prolification and in multiplication the adventitious structures are of independent origin. In fission the new developments grow simultaneously with the older ones, of which, indeed, they are mere repetitions. Moreover, in fission the supplementary lobes do not, in general, project a plan different from that of the original structure, at least in the first instance, though their direction may ultimately become changed.

In enation the new growth projects from a previously formed organ after it has attained to considerable size, or even after its ordinary proportions have been attained, and it sprouts out from the beginning in a plane which is at a considerable angle to that of the parent organ, and it is sometimes of a different structure from it, and has different functions to fulfil.

Many of the instances that occur of scales projecting from petals, as inCaryophylleæ,Sapindaceæ, &c., the coronal filaments of passion-flowers, the cup ofNarcissus, the appendages that beset the segments of the perianth inLilium lancifolium, and other similar growths, may be referred to a like process. In many cases this has been proved by a study of the development of the flower, from which it appears that the growths in question are developed subsequently to the formation of the ordinary floral whorls. It is requisite, however, to be cautious in pronouncing upon the exactnature of these bodies, in the absence of a knowledge of their period and mode of formation. They may be mere outgrowths from one or other of the customary whorls, or they may represent abortive stamens or petals, &c. Where circumstances prevent the course of development from being traced, something may be inferred as to their real nature from their position in regard to the other parts of the flower, from their anatomical structure, and from analogy or comparison with like organs in other plants. The period of their formation is, perhaps, of less importance than was at one time supposed, since it is well ascertained that, in some cases, the formation of the parts of the flower,e.g.the stamens of mallows, follows a centrifugal rather than a centripetal order.

In the case of monstrous developments of this nature too much care can hardly be exercised, and the observer should rarely venture on an explanation of the nature of the case from the evidence afforded by the monstrous growth apart from that to be derived from the study of the development and organization of the normal flower and from analogous formations in allied plants.

Excrescences from axile organs—Warts.—In a preceding paragraph the formation of gnaurs has been alluded to. There are other outgrowths, called warts, occasionally met with in trees, and which are more closely connected with the central tissues of the stem, while at the same time they are not provided with buds, in which two particulars warts differ from gnaurs.

Excrescences of this kind often attain a very large size, and may be seen on old elms and other trees, but, as their formation is probably more pathological than teratological, no further notice of these structures need here be given. No special notice need here be taken of the tubercles on the roots of so manyLeguminosæ, nor of the peculiar excrescences on the roots ofTaxodium distichum, as these appear to be normal formations. But it may be well to mention in thisplace an anomalous development which occurs occasionally inRuscus aculeatus, and in which, from the upper surface of the ordinary flattened leaf-like branch, projects at right angles a second similar branch, so that in section the appearance would be like that of the inverted letter t; thus, [symbol: Inverted upper-case T].

Enation from foliar organs—Leaves.—The development of adventitious lobes from leaves may take place either from their surfaces or their margins. A few illustrations may be given of each. In cabbage leaves a formation of adventitious laminæ projecting at right angles from the primary one may frequently be observed. In the instance figured (fig. 210) the new growths proceeded almost exclusively from the thick midrib, which, in the figure, is shown cut through just above the base. Not only is the ordinary semilunar band of vascular tissue to be here seen, but a similar broken line of vessels exists on the upper side of the leaf-stalk; thus the whole structure resembles that of a stem or a branch as much as that of a true leaf.

Fig.210.—Section through base of midrib of cabbage leaf, showing supplementary laminæ, &c.

The development of secondary leaves from the surfaces of primary ones (phyllomania, autophyllogeny) has already been alluded to atp. 355.

Some of the cases wherein a leaf seems to have a double lamina may be alluded to here, though possibly they would more properly be referred to fission. The appearance presented is as if four wings projected from the midrib, so that a cross section would be nearly in the form of [Symbol: )O( turned 90 degrees.]. In an orange leaf presenting this appearance the lower surface of one lamina was, as usual, dull in colour, while the upper surface of the subjacent lamina was likewise dull; hence the impression might arise that this was an instance of the adhesion of two leaves back to back, but the petioles were not twisted, as they must have been had two leaves thus been united, and neither in the petiole nor in the midrib was there the slightest indication of fusion, the vascular bundles being arranged in a circular manner, not in a horseshoe-like arrangement, as would have been the case had adhesion taken place.[518](See p. 33.)

Such leaves as those of the hedgehog holly,Ilex Aquifolium, var.feroæ, and, to a less extent, bullate leaves, may also be mentioned here as illustrations of hypertrophy or enation.

Fig.211.—Nephrodium molle. Ordinary frond and forked and crested varieties of the same, the crest arising from the inordinate development of the margins of the pinnules.

When the increased development occurs at the margin of the leaves, especially, the result is a wavy or crisped appearance, "folia undulata,velcrispa."[519]Theseconditions occur normally in such leaves as those ofRumex crispus,Malva crispa, &c., and are developed to an extreme degree in garden varieties of parsley, some kails, &c., as well as in many ferns, but these are probably cases rather of fission than enation as here understood.[520]

Enation from the sepals.—The basal lobes of the calyx inCampanula Medium, under normal circumstances, may be referred to in illustration of this occurrence, while the adventitious spurs on the calyx of some monstrous flowers seem due also to a like cause. These have already been alluded to at p. 315.

Enation from the corolla.—The instances of this are more frequent than in the case of the calyx, and admit of classification according as they occur in polypetalous or gamopetalous flowers, on the outer or inner surface of the petals, &c. Under natural circumstances the formation of scales, lobes, &c., from the petals, as in someCaryophylleæ,Sapindaceæ, &c. &c., may be explained, as already remarked, by this process, rather than by fission, chorisis, or by substitution of petals for stamens, &c. Each case must, however, be examined on its own merits, as it is not safe to decide upon the arrangement of parts in one flower by simply referring to the analogy of others. In the following illustrations the course of development has not, in all cases, been observed, and hence the explanation here given must be taken with some reserve; for should it prove that the adventitious lobes, &c., are formed simultaneously with the ordinary petals, the case will be one of chorisis rather than of enation, as here understood. Again, it may be that the supernumerary organs really represent petals or stamens in disguise, though this hypothesis demands the further assumption (in order to account for the interference with the lawof alternation) that suppression of certain organs has taken place.

Taking first those instances in which the supplementary petals appear on the inner surface of the corolla, as being at once the most frequent, and as presenting the closest analogy, with similar conformations, under natural circumstances, certain double-flowered varieties of the Chinese primrose,Primula sinensis, may be mentioned. In these flowers the calyx is normal, the tube of the corolla is traversed by ten vascular bundles, and the limb is divided into ten fimbriated lobes. About halfway up the tube, on the inner surface, are given off five supernumerary petals, opposite to as many lobes of the corolla. Some of the supplementary petals have a stamen in front of them, in the same relative position as in the normal flower. In some cases the back or outer surface of the supplementary petal is turned towards the inner or upper surface of the primary corolla, thus [Symbol: ((turned 90 degrees cw]; while, in other instances, the front of the adventitious lobe is directed towards the corresponding surface of the original petal, thus [Symbol: () turned 90 degrees]. Whether these supernumerary petals are formed by chorisis or by enation cannot, with certainty, be determined without examining the early stages of development.

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