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

[507] 'Mem. 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, "Memoire sur les graines charnues des Amaryllidees," &c.; 'Ann. Sc. Nat.,' 1860, vol. xiv, p. 1, tab. 1.

CHAPTER II.

ELONGATION.

The cla.s.s 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 in _Ranunculus fluitans_, the flower-stalks of _Valisneria spiralis_, &c. These are cases of variation rather than of malformation, but are none the less curious, or sometimes perplexing; thus, Lapeyrouse described, in his 'Supplement a la flore des Pyrenees,' p. 27, under the name _Potamogeton bifolium_, a plant which Mr. Bentham subsequently discovered to be nothing but a flowerless variety of _Vicia Faba_ distorted 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 pa.s.sed 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, among _Umbelliferae_ the 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 some _Leguminosae_, _Trifolium repens_, &c. &c.

Another ill.u.s.tration of the sort is that recorded by M. Fournier, wherein the usually umbellate inflorescence of _Pelargonium_ was, 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 Schonefeld 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 a.s.sociation 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 many _Amentaceae_. (See p. 204, figs. 105, 106.)

A lengthening of the axis of the female strobiles of _Coniferae_ is not of infrequent occurrence in _Cryptomeria j.a.ponica_, _Larie europaea_, &c., and this is usually a.s.sociated, 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 in the 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 of _Ranunculus 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 in _Trifolium repens_, _Lotus corniculatus_, &c., what is usually a compact spike, or head of flowers, becomes a raceme from the elongation of the pedicels. In _Umbelliferae_ a similar change occurs, by virtue of which sometimes the umbels themselves, and at other times the florets, are raised on unusually long stalks, as in _Angelica Razoulzii_, _Carum Carui_, _Thysselinum pal.u.s.tre_.[513] In _Compositae_, when affected by an a.n.a.logous change, the capitulum a.s.sumes the appearance of a simple umbel, as in _Hypochaeris radicata_, _Senecio vulgaris_, and other plants.

[Ill.u.s.tration: FIG. 206.--Inflorescence of _Ranunculus 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 of _Umbelliferae_ and _Compositae_, 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 ill.u.s.trations 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 instances the 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.

[Ill.u.s.tration: 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 of _Potentilla_.[514]

=Elongation of the parts of the flower.=--The only circ.u.mstance that needs especial mention under this section is the great lengthening that sometimes takes place in the carpels, sometimes as a result of injury from insects or fungus, at other times without a.s.signable cause.

[Ill.u.s.tration: FIG. 208.--Leaves of horse-chestnut, _aesculus_, showing pa.s.sage from digitate to pinnate leaves.]

In the case of inferior ovaries this lengthening is, perhaps, even more common, as in _Umbelliferae_, _Compositae_, &c. The common groundsel (_Senecio vulgaris_) is especially liable to this form of enlargement of the pistil, either in a.s.sociation with a leafy condition of the pappus or without any such change.

=Elongation of the thalamus, placenta, &c.=--In some plants, as in _Magnolia_ or _Myosurus_, the thalamus becomes much elongated, and bears the carpels disposed spirally around it. A similar lengthening occurs in malformed flowers, usually in a.s.sociation 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 gynoph.o.r.es, androph.o.r.es, &c., of _Pa.s.sifloreae_, _Caryophylleae_, _Capparideae_, &c. &c.

A similar elongation of the thalamus, bringing about the separation of the floral whorls, or of their const.i.tuent parts, is very commonly met with in a.s.sociation with median prolification. Where the individual floral elements are thus thrown out of their usual verticillate arrangement, they naturally a.s.sume 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 of _Anagallis phoenicea_ was separated by a rather long internode from the corolla, and a like ill.u.s.tration in _Torilis Anthriscus_.

[Ill.u.s.tration: FIG. 209.--Flower of _Delphinium_, 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.

In _Tropaeolum majus_ a similar elevation of the pistil may occasionally be seen.

The adjacent figure of a monstrous _Delphinium_ taken from Cramer ill.u.s.trates 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 ill.u.s.trations of these changes occurs in a permanent malformation of _Epilobium 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. In _Fuchsia_ and _Campanula_ a 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 Chamaedrys_, _Orobanche gracilis_, _Solanum Lycopersic.u.m_, _Gentiana campestris_, _Hyperic.u.m_, _h.e.l.leborus fetidus_, _Caltha pal.u.s.tris_, _Bra.s.sica oleracea!_ and many _Rosaceae_, _Caryophylleae_, _Cruciferae_, and _Ranunculaceae_. (See Dialysis, Median Prolification, &c.)

Apostasis of the sub-floral or involucral leaves is not of infrequent occurrence in malformations affecting _Compositae_ and _Umbelliferae_. 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. Cla.s.s.,' 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; 'Linnaea,' xi, p. 301, xiv, p. 363; 'Bot. Zeit.,' 1856, p. 72; Masters, 'Rep. Brit. a.s.soc.,'

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.