FOOTNOTES:

[295] 'Neue Denkschrift. Schweiz. Gesellsch.,' band v, p. 9.

[296] 'Bull. Acad. Belg.,' xix, part 2, p. 93.

[297] Schlechtendal, 'Linnæa,' ix, p. 737.

[298] Misbilld., 'Cult. Gewachs.,' p. 32.

[299] Linn., 'Phil. Botan.,' § 120.

[300] 'Bull. Soc. Bot. France,' 1859, vol. vi, p. 199.

[301] Seemann's 'Journal of Botany,' vol. iii, p. 105; also Morren, 'Bull. Acad. Belg.,' vol. xx, part 2, p. 264.

[302] Morren, 'Bull. Belg.,' xviii, p. 503.

[303] 'Organ. Vég.,' t. i, p. 513.

[304] 'Bull. Acad. Roy. Belg.,' tome xvii; and Lobelia, p. 65.

[305] Masters, "On Double Flowers," 'Rep. Internat. Bot. Congress,' London, 1866. p. 127.

[306] See also C. Morren, "Sur les vraies fleurs doubles chez les Orchidées," 'Bull. Acad. Roy. Belg.,' vol. xix, part ii, 1852. p. 171.

[307] C. Morren, 'Bull. Acad. Belg.,' vol. xx, 1853, part ii, p. 284 (Syringa).

[308] 'Rep. Bot. Congress,' London, 1866, p. 135, t. vii, f. 14.

[309] Although it is generally admitted that the filament of the stamen corresponds to the stalk of the leaf, and the anther to the leaf-blade, yet there are some points on which uncertainty still rests. One of these is as to the sutures of the anther. Do these chinks through which the pollen escapes correspond (as would at first sight seem probable) to the margins of the antheral leaf, or do they answer to the lines that separate the two pollen-cavities on each half of the anther one from the other? Professor Oliver, 'Trans. Linn. Soc.,' vol. xxiii, 1862, p. 423, in alluding to the views held by others on this subject, concludes, from an examination of some geranium flowers in which the stamens were more or less petaloid, that Bischoff's notion as to the sutures of the anther is correct, viz., that they are the equivalents of the septa of untransformed tissue between the pollen-sacs. Some double fuchsias ('Gard. Chron.,' 1863, p. 989) add confirmation to this opinion. In these flowers the petals were present as usual, but the stamens were more or less petaloid, the filaments were unchanged, but the anthers existed in the form of a petal-like cup from the centre of which projected two imperfect pollen-lobes (the other two lobes being petaloid). Now, in this case, the margins of the anther were coherent to form the cup, and the pollen was emitted along a line separating the polliniferous from the petaloid portion of the anther. This view is also borne out by the double-flowered Arbutus Unedo, and also by what occurs in some double violets, wherein the anther exists in the guise of a broad lancet-shaped expansion, from the surface of which project four plates (fig. 157), representing apparently the walls of the pollen-sacs, but destitute of pollen; the chink left between these plates corresponds thus to the suture of the normal anther.

Fig. 157.—Petaloid stamen of Viola, with four projecting plates.

The inner or upper portion of the anther-leaf is that which is most intimately concerned in the formation of pollen; it comparatively rarely (query ever) happens that the back or lower surface of the antheral leaf is specially devoted to the formation of pollen. On the other hand, in cases like those of the common houseleek, where we meet with petaloid organs combining the attributes of anthers and of carpels, we find the inner layers devoted to the production of pollen, the outer to the formation of ovules.

That the pollen-lobes are not to be taken as halves of a staminal leaf, but rather as specialised portions of it, not necessarily occupying half its surface, is shown also in the case of double-flowered Malvaceæ, in which the stamens are frequently partly petal-like, partly divided into numerous separate filaments, each bearing a one-, or it may be even a two-lobed anther. This circumstance is confirmatory of the opinion held by Payer, Duchartre, Dickson, and other organogenists, as to the compound nature of the stamens in these plants. The stamens are here analogues not of a simple entire leaf, but of a lobed, digitate, or compound leaf, each subdivision bearing its separate anther. On this subject the reader may consult M. Müller's paper on the anther of Jatropha Pohliana, &c., referred to at page 255.

[310] See C. Morren, "On Spur-shaped Nectarines," &c., 'Ann. Nat. Hist.,' March, 1841, p. 1. tab. 11.

[311] Karsten, 'Flor. Columb. Spec.,' tab. xxix.

[312] See Dickson, "On Diplostemonous Flowers," 'Trans. Bot. Soc. Edin.,' vol. viii, p. 100; and on the Andrœcium of Mentzelia, &c., in Seemann's 'Journal of Botany,' vol. iii, p. 209, and vol. iv (1866) p. 273 (Potentilla, &c.).

[313] See Baillon, 'Adansonia,' iii, p. 351, tab. 12, Sinapis.

[314] 'Bull. Acad. Belg.,' xvii, part i, p. 516, c. tab., and 'Lobelia,' p. 83.

[315] Cited in 'Bull. Soc. Bot. France,' xiv, p. 253 ('Rev. Bibl.').

[316] 'Bull. Soc. Bot. Fr.,' 1858, p. 331.

[317] 'Mem. Legum.,' p. 44.

[318] 'Bildungsabweich, 'Pflanz. Fam.,' tab. 8, f. 12.

[319] 'Atlas de Göthe' p. 55, t. 4, f. 18.

[320] Wiegmann, 'Bot. Zeit.,' 1831, p. 5, tab. i.

[321] 'Ic. Flor. Germ.,' xiii, tab. 112, cccclxiv, f. 2.

[322] Seemann's 'Journal of Botany,' 1867, p. 317, t. 72, A (Ophrys).

[323] 'Enum. Euphorb.' p. 53.

[324] 'Linnæa.' i, p. 457.

[325] 'De Balsam,' p. 17.

[326] B. Clarke, 'Arrangement of Phænog. Plants,' p. 23.

[327] See 'Engelmann,' p. 26, tab. 3, f. 10, 11, 14.

[328] 'Ann. Sc. Nat.,' ser. 2, t. viii, 1837, p. 58.

[329] 'Bot. Zeit.,' 4, 1846, 889.

[330] 'Verhandl. Nat. Hist. Ver. Preuss. Rheinl. und Westph.,' 1858, 1860, p. 381. Cramer also, 'Bildungsabweich,' p. 90, cites a case in Pæonia where the carpel was open and petaloid, and bore an anther on one margin, and four ovules on the other.

[331] 'Euphorbiaceæ,' p. 205.

[332] Seemann's 'Journ. Bot.,' iv, p. 168, tab. 47, f. 1.

[333] Moquin-Tandon, l. c., 220, Passiflora. Masters, 'Journ. Linn. Soc.,' 1857, p. 159, Saponaria. Seemann's 'Journ. Botany,' vol. iii, p. 107, Narcissus.

[334] 'Bull. Soc. Bot. Fr.,' 1857, p. 452.

[335] 'Gardeners' Chronicle,' 1866, p. 897.

[336] Maout, 'Leçons Element.,' vol. ii, p. 488.

[337] Poiteau and Turpin, 'Arb. Fruit,' t. 37, and Trécul, 'Bull Soc. Bot. France,' vol. i. p. 307.

[338] Clos, 'Mem. Acad. Toulouse,' 5 ser., vol. iii.

[339] 'Bot. Zeit.,' 1850, t. viii, pp. 514, 664. 'Flora,' (B. Z.) 1832, t. xv, p. 252; also cited in 'Ann. des Serres et des jardins,' vi, pp. 241–5. See also Schlechtendal, 'Bot. Zeit.,' 1845, t. 3, p. 6.

[340] 'Bull. Soc. Bot. France,' t. viii, p. 453.

[341] See also Allmann, 'Rep. Brit. Assoc.,' July, 1851.

[342] 'Theory of Horticulture,' ed. 2, p. 82.

[343] 'Mém. Soc. Hist. Nat. Paris.' i, 16.

[344] Gen. Munro, 'Trans. Linn. Soc.,' xxvii, p. 7.

[345] 'Bull. Soc. Bot. Fr.,' 1857, p. 21.

[346] 'Ann. Scienc. Nat.,' t. viii, 1837, p. 50, and 'Bot. Zeit.' (R.), 1836, t. xix, p. 513, &c. See also MM. Sourd Dussiples and G. Bergeron, 'Bull. Soc. Bot. France,' viii, p. 349; Von Schmidel, 'Icon. plant. et Anal. part.' 1782, p. 210, fig. 54.

[347] Godron, 'Bull. Soc. Bot. Fr.,' xiii, p. 82, Rev. Bibl.

[348] Cited in Henfrey, 'Bot. Gazette,' iii, p. 12.

[349] 'Ann. Nat. Hist.,' September, 1856, p. 56. See also Kirschleger, 'Flora (Bot. Zeit.),' xxiv, 1841, p. 340, Salix alba. Henschel, 'Flora (Bot. Zeit.),' 1832, t. xv, p. 253, S. cinerea. Hartmann, 'Flora (Bot. Zeit.),' xxiv, p. 199, S. nigricans. Meyer, C. A., 'Bull. Phys. Math.,' t. x, S. alba.

PART IV.
HETEROMORPHY.

There are certain malformations that have little in common beyond this, that they cannot readily be allocated in either of the great groups proposed by writers on teratology. There are also deformities which, unlike the majority of deviations from the ordinary structure, are absolute and not relative. While the latter are due to an exaggeration, or to an imperfection of development, or, it may be, to a partial perversion in organization, the former differ from the normal standard, not merely in degree, but absolutely. This is often the case when disease or injury affects the plant; for instance, in the case of galls arising from insect-puncture the structure is rather a new growth altogether, than dependent on mere hypertrophy of the original tissues. These absolute deformities arising from the causes just mentioned belong rather to pathology than to teratology strictly so called; but, under the head of deformities, may be mentioned sundry deviations not elsewhere alluded to.

CHAPTER I.
DEFORMITIES.

The special meaning here attached to the term deformity is sufficiently explained in the preceding paragraph; it remains to give a few illustrations, and to refer to other headings, such as Heterotaxy, Hypertrophy, Atrophy, &c., for malformations capable of more rigid classification than those here alluded to.

Fig. 166.—Portion of the under surface of a cabbage-leaf, with horn-like excrescences projecting from it.

Formation of tubes.—The production of ascidia or pitchers from the cohesion of the margins of one or more leaves has been already alluded to ([see pp. 21], [30]), but there is another class of cases in which the tubular formation is due, not so much to the union of the margins of a leaf as to the disproportionate growth of some portions as contrasted with others, whence arises either a depressed cavity, as in the case of a leaf, or an expanded and excavated structure, when the stem or some portion of it is affected.

The fruit of the rose, the apple, the fig, and many others, is now generally admitted to be composed externally of the dilated end of the flower-stalk in which the true carpels become imbedded. Between such cases and that of a peltate leaf with a depressed centre, such as often occurs, to some extent, in Nelumbium, there is but little difference.

In cabbages and lettuces there not unfrequently occurs a production of leaf-like processes projecting from the primary blade at a right angle (see Enation). Sometimes these are developed in a tubular form, so as to form a series of little horn-like tubes, or shallow troughs, as in Aristolochia sipho. At other times the nerves or ribs of the leaf project beyond the blade, and bear at their extremities structures similar to those just described.

Fig. 167.—Lettuce leaf, bearing on the back a stalked cup, arising from the dilatation of the stalk (?).

In a variety of Codiæum variegatum a similar formation may be seen to a minor extent. Even the common Scolopendrium vulgare occasionally produces small pitchers of this character, as in the varieties named perafero-corautum, Moore, and peraferum, Woll.[350]

In carnations leaves may sometimes be seen from both surfaces, from which project long, sharp-pointed tubular spurs at irregular intervals. A very singular illustration of this is figured by Trattinick,[351], in which the leaves, epicalyx, sepals, and petals, were all provided with tubular spurs.

In Cephalotus follicularis rudimentary or imperfect pitchers may be frequently met with, in which the stalk of the leaf is tubular and bears at its extremity a very small rudimentary leaf-blade. It is not in all cases easy to trace the origin and true nature of the ascidium, as the venation is sometimes obscure. If there be a single well-marked midrib the probability is that the case is one of cohesion of the margins of the leaf; but if the veins are all of about equal size, and radiate from a common stalk, the pouch-like formation is probably due to dilatation and hollowing of the petiole. Again, when the result of a union of the margins of the leaf, the pitcher is generally less regular than when formed from the hollowed end of a leaf-stalk. Further information is especially needed as to the mode of development and formation of these tubular organs, so as to ascertain clearly when they are the result of a true cupping process, and when of cohesion of the margins of one or more leaves. (See Cohesion, p. 31. For bibliographical references consult also A. Braun, 'Flora v. Bot. Zeit.,' 1835, t. xviii, p. 41, Aristolochia.)

Tubular formations in the flower.—A similar formation of tubes happens in some double flowers; for instance, it is not infrequent in double flowers of Primula sinensis, in which tubular petal-like structures are attached to the inner surface of the corolla; sometimes these petaloid tubes replace the stamens, while at other times they appear to have no relation to those organs. In the particular flowers now alluded to the tubular form seems due to a dilatation, and not to a cohesion of the margins. (See Cohesion, p. 23.) These tubular petals resemble in form and colour almost precisely the normal corolla in miniature, but are not surrounded by a calyx, nor do they contain stamens, while the less perfect forms show clearly their origin from a single tube-like organ.

Fig. 168.—Corolla of Primula sinensis turned back to show a tubular petal springing from it. One only is shown for the sake of clearness; they are generally numerous.

The formation of spurs or spur-like tubes in a quasi-regular manner has been spoken of under the head of Irregular Peloria, p. 228, but we occasionally meet with tubular processes which seem to occur in an irregular manner, and to have no reference to the symmetrical plan of the flower, and which are due probably to the same causes as those which induce hypertrophy. Such spurs have frequently been seen on the corolla of Digitalis purpurea, Antirrhinum majus,[352] Tulipa Gesneriana, and occasionally on the sepals of Fuchsia. They are very frequent in some seasons in the corolla of certain calceolarias (C. floribunda). By Morren this production of adventitious spurs was called "Ceratomanie."

Fig. 169.—Corolla of Calceolaria, showing irregular tubular spurs projecting from the lower lip.

Similar processes may sometimes be seen in the capsules of Linaria vulgaris, as also in the fruits of some of the Solanums, quite without reference to the arrangement of the carpels, so that their production seems to be purely irregular.

Morren, as previously remarked, gave the name "Solenaidie" to tubular deformities affecting the stamens, a term which has not been generally adopted; the deformity in question is by no means of uncommon occurrence in some double or partially pelorised flowers, as Antirrhinum, Linaria, &c. A similar formation of conical out-growths may frequently be met with in the fruits quite irrespectively of any disjunction of the carpels.

Contortion.—An irregular twisting or bending of the stem or branches is by no means of uncommon occurrence, the inducing causes being often some restriction to growth in certain directions, or the undue or disproportionate growth in one direction, as contrasted with that in another. Hence it may arise from insect-puncture, parasitic growth, or any obstacle to the natural development. Frequently it exists in conjunction with fasciation, the ends of the branches being curved round like a shepherd's crook, from the growth on one side being so much greater than on the other. Sometimes it is a mere exaggeration of a normal condition; thus, in what are termed flexuose stems the stem twists alternately to one side or another, frequently in association with an oblique form of the leaf. This state is sometimes present to an extreme degree, as in some varieties of shrubs (Cratægus, Robinia, &c.) cultivated for their singularly tortuous branches.

Fig. 170.—Portion of the culm of a Juncus, bent irregularly.

Fig. 171.—Portion of a branch of Cratægus oxyacantha, var. tortuosa.

Such cases as those just mentioned, however, are but slightly irregular compared to others in which the deformity exists to such an extent that the traces of the ordinary mode of growth are almost obliterated. M. Moquin-Tandon[353] alludes to a case of this kind in a species of pine (Pinus), in which a branch ended in four unequal divisions, which were strongly curved from without inwards, then became united in pairs, these latter in their turn blending into a single mass.

In the case of some beeches growing in the forest of Verzy, near Rheims, the trunks of the trees are contorted in every direction, and, at a height of from fifteen to twenty feet, a number of branches are also given off, also much contorted, and occasionally intergrafted, so that it seems as if a heavy weight had been placed on the trees and literally flattened them. Similar malformations may occasionally be met with in the branches of the oak, and commonly in the weeping ash.

M. Fournier[354] mentions the stems of Ruscus aculeatus rolled in a circle, others twisted spirally.

The phenomenon is not confined to woody plants, but has been met with in chicory, in Antirrhinum, and other herbaceous species.

It is very difficult in some cases to separate these instances of irregular torsion from those in which the twisting takes place in a more or less regular spiral direction. In the former case the fibres of the plant are only indirectly involved, but in the latter the fibres themselves are coiled spirally from right to left, or vice versâ (spiral torsion), while not unfrequently both conditions may be met with at the same time.

The leaves also are subject to similar deformities, of which a notable illustration has been recorded in the case of the date palm, Phœnix dactylifera, originally observed by Goethe, and figured and described by Jaeger;[355] the leaves are folded and twisted in every direction, in consequence of the fibrous band or cord which surrounds the leaves, and which generally breaks as the leaflets increase in size, remaining from some cause or other unbroken, and thus serving to restrain the growth.

A similar irregularity of growth occurs, not unfrequently, in the case of crocus leaves, when in the course of their growth, as they push their way through the soil, their progress becomes checked either by a stone or even by frost.

Spiral torsion.—Growth in a spiral direction, and the arrangement of the various organs of the plant in a spiral manner, are among the most common of natural phenomena in plants.[356] Fibres are coiled spirally in the minute vessels of flowering plants, and are not wholly wanting even among fungi. The leaf-organs are very generally spirally arranged; the leaf-stalks are often so twisted as to bring leaves on one plane which otherwise would occupy several. In the leaf itself we have a spiral twist taking place constantly in Alstrœmeria, in Avena, and other plants. A similar tendency is manifested in the flower-stalks, as in Cyclamen and Vallisneria, and the whole inflorescence, as in Spiranthes. Even the bark and wood of trees is often disposed spirally. This is very noticeable in some firs, and in the bark of the sweet chestnut (Castanea), of Thuja occidentalis, and other trees. The knaurs or excrescences which are sometimes found on the roots or stems of trees afford other illustrations of this universal tendency. These bodies consist of a number of embryo buds, which, from some cause or other, are incapable of lengthening. On examination every rudimentary or undeveloped bud may be seen to be surrounded by densely crowded fibres arranged spirally.

The axes of nearly all twining plants are themselves twisted, and twisted in a direction corresponding to the spontaneous revolving movement exhibited by these plants, as in the hop, the convolvulus, passion flower, &c., the degree of twisting being dependent to a great extent on the roughness of the surface around which the stem twines[357].

Considered as an exceptional occurrence, it occurs frequently in certain plants, and, when it affects the stem or branches, necessarily causes some changes in the arrangement of the parts attached to them; thus, spiral torsion of the axial organs is generally accompanied by displacement of the leaves, whorled leaves becoming alternate, and opposite or whorled leaves becoming arranged on one side of the stem only. Frequently also this condition is associated with fasciation, or, at least, with a distended or dilated state. An illustration of this in Asparagus has been figured at p. 14.

Very often the leaves are produced in a spiral line round the stem, as in a specimen of Dracocephalum speciosum described and figured by C. Morren. The leaves of this plant are naturally rectiserial and decussate, but, in the twisted stem the leaves were curviserial, and arranged according to the 5/13 plan. Now, referring to the ordinary notation of alternate leaves, we shall have the first leaf covered by the fifth, with two turns of the spiral; since decussate leaves result from two conjugate lines, the formula will be necessarily 2/5. The fraction 5/13 hence comes regularly into the 2/5 series (2/5, 3/8, 5/13). Thus, the leaves in assuming a new phyllotaxy, take one quite analogous to the normal one.

One of the most curious instances that have fallen under the writer's own observation occurred in the stem of Dipsacus fullonum. (See 'Proceedings of the Linnean Society,' March 6, 1855, vol. ii, p. 370). The stem was distended, and hollow, and twisted on itself; its fibres, moreover, were arranged in an oblique or spiral direction; the branches or leaf-stalks, which usually are arranged in an opposite and decussate manner, were, in this case, disposed in a linear series, one over the other, following the line of curvature of the stem. When the course of the fibres was traced from the base of one of the stalks, upward around the stem, a spiral was found to be completed at the base of the second stalk, above that which was made the starting point. Now, if opposite leaves depend on the shortened condition of the internode between the two leaves, then, in the teazel-stem just described, each turn of the spiral would represent a lengthened internode; and, if the fibres of this specimen could be untwisted, and made to assume the vertical direction, and, at the same time, the internodes were shortened, the result would be the opposition of the branches and the decussation of the pairs; this explanation is borne out by the similar twisting which takes place so frequently in the species of Galium and other Rubiaceæ.

Fig. 172.—Twisted stem of Dipsacus fullonum.

G. Franc[358] was one of the first to notice this twisting in Galium, and M. Duchartre,[359] in mentioning a similar instance, gives the following explanation of the appearance which will be found to apply to most of these cases. In the normal stem of Galium Mollugo the branches are opposite in each verticil and crossed in the two successive ones. The stem is four-angled, each angle having a nerve. Each of these nerves, springing from the origin of a branch in one whorl, terminates in the interval which separates the point of origin of the two branches in the whorl next above it. In the deformed stem one of the nerves corresponds to the insertion of a branch, its neighbour is in the adjoining vacant space; hence it results that four nerves correspond to two branches and to two consecutive interspaces, and hence the analogy between a single normal internode provided with its two branches and its four nerves. What confirms this inference is that the nerve, which begins at the point of origin of a branch, after making one spiral turn round the stem, terminates in the interval that separates the two following branches, just as in a branch of the normal stem it ends in the upper whorl between the two next branches. The torsion, then, in this Galium caused the separation of the two opposite branches of the same verticil, and placed them one above another, and this being reproduced in all the whorls, all the branches come to be arranged on the same longitudinal line. The leaves are susceptible of the same explanation; they are inserted in groups of three or four in one arc round the origin of each branch. In the malformation each series or group of four leaves, with its central branch, is equivalent to half a whorl of the natural plant with its axillary branch. In other words, the malformation consists in a torsion of the stem, which separates each whorl into two distinct halves; these half-whorls, with their axillary branches, are placed on a single longitudinal series one above another. This case is quoted at some length, as it is an admirable example of a very common form of malformation in these plants.

In some parts of Holland where madder is cultivated a similar deformation is particularly frequent. The leaves, however, are not always grouped in the way in which they were described by M. Duchartre, but more commonly form a single continuous line; when arranged in leaf-whorls it generally happens that some of the leaves are turned downwards, while others are erect. It has been said that this condition occurs particularly frequently in plants growing in damp places. It is certainly true that spiral torsion of the stem is specially frequent in the species of Equisetum, most of which grow in such spots. In these plants either the whole of the upper part of the stem is thus twisted, or a portion only: thus Reinsch[360] cites a case in Equisetum Telmateia, where the upper and lower portions of the stem were normal, while the intermediate portion was twisted spirally. In this instance the whorl next beneath the spiral had twenty-eight branchlets, and that immediately above it thirty. Along the course of the spire there were two hundred and three; dividing this latter number by the mean of the two preceding, it was seen that the spire included the constituents of seven ordinary verticils.

Fig. 173.—Stem of Galium spirally twisted. From a specimen communicated by Mr. Darwin.

Here also may be mentioned a curious bamboo, the stem of which is preserved in the British Museum, and in which the internodes, on the exterior, and the corresponding diaphragms and cavities within are spiral or oblique in direction.

The root is also subject to the same malformation, the inducing cause being usually some obstruction to downward growth, as when a plant has been grown in a small pot, and becomes, as gardeners say, pot-bound.

Fig. 174.—Showing "pot-bound" root twisted spirally (from the 'Gard. Chron.,' 1849).

The axial portion of the flower, the thalamus, is also occasionally twisted in a spiral direction, the lateral parts of the flower being in consequence displaced. Morren spoke of this displacement of the floral organs as "speiranthie."[361]

Morren draws a distinction between spiral-torsion or spiralism and the less regular torsion spoken of in the preceding section; in the former case not only is the axis twisted, but its constituent fibres also. The condition in question in some cases seems to be inherited in the seedling plants.

The following is a list of the plants in which spiral torsion of the stem or branches has been most frequently observed. (See also under Fasciation and Contortion.)

Among the more important papers relating to this subject may be mentioned:

Moquin-Tandon, 'El. Ter. Veg.,' p. 181. Kros, 'De Spira in plantis conspicua.' Morren, 'Bull. Acad. Roy. Belg.,' 1851, tom. xviii, part i, p. 27. Milde, 'Nov. Act. Acad. Leop. Carol. Nat. Cur., 1839. Ibid., vol. xxvi, part ii, p. 429, Equisetum. Irmisch, 'Flora,' 1858, t. ii, Equisetum. Vrolik, 'Nouv. Mem. Instit. Amsterdam,' Lilium. Schlechtendal, 'Bot. Zeit.,' xiv, p. 69, et v, p. 66. De Candolle, 'Organ. Veget., t. i, p. 155, tab. xxxvi, Mentha, &c. Alph. de Candolle, 'Neue Denkschr. Allg. Schweiz. Gesellschft.,' band v, tab. vi, Valeriana. Duchartre, 'Ann. Sc. Nat.,' ser. 3, vol. i, p. 292. 'Gardeners' Chronicle,' July 5, 1856, p. 452, c. ic. xylogr., spiral branches from Guatemala—tree not known.

Spiral twisting of the leaf is scarcely of so common occurrence as the corresponding condition in the stem. In Alstrœmeria it occurs normally, as also in some grasses. In the variety annularis of Salix babylonica the leaf is constantly coiled round spirally. A similar contortion occurs in a variety of Codiæum variegatum lately introduced from the islands of the South Seas by Mr. J. G. Veitch.

Fern fronds are occasionally found twisted in the same manner, e.g. Scolopendrium vulgare var. spirale.[362]

Adventitious tendrils.—Under ordinary circumstances tendrils may be described as modifications of the leaf, the stipule, the branch, or of the flower stalk, so that it is not a matter of surprise to find tendrils occasionally springing from the sepals or petals, as indeed happens normally in Hodgsonia, Strophanthus, &c.

M. Decaisne[363] found a flower of the melon in which one of the segments of the calyx was prolonged into a tendril, and Kirschleger records a similar instance in the cucumber, while Mr. Holland ('Science Gossip,' 1865, p. 105) mentions a case in which one of the prickles on the fruit of a cucumber had grown out into a tendril.

In Cobæa scandens the foliar nature of the tendril is shown by the occasional presence of a small leaflet on one of the branches of the tendril, and a similar appearance may frequently be seen in Eccremocarpus scaber. On the other hand, in the vine, the axial nature of the tendril is revealed by the not infrequent presence of flowers or berries on them, as also in Modecca and some Passifloraceæ.

Darwin, speaking of the tendrils of Bignonia capreolata, says it is a highly remarkable fact that a leaf should be metamorphosed into a branched organ, which turns from the light, and which can, by its extremities, either crawl like a root into crevices, or seize hold of minute projecting points, these extremities subsequently forming cellular masses, which envelope by their growth the first fibres and secrete an adhesive cement.

Interrupted growth.—This term is here used in the same sense as in ordinary descriptive botany, as when an "interruptedly pinnate" leaf is spoken of. A similar alternation may be observed occasionally as a teratological occurrence, though it is not easy to account for it.

Fig. 175.—Interrupted growth of Radish (from the 'American Agriculturist.')

Fig. 176.—Interrupted growth in Apple.

Fig. 175 shows an instance of the kind in a radish, and fig. 176 a similar deformity in the case of an apple, the dilatation of the flower-stalk below the ordinary fruit producing an appearance as if there were two fruits one above another.

In leaves this peculiar irregularity of development is more common.

In some varieties of Codiæum variegatum the leaves resemble those of Nepenthes, as the basal portion is broad, and terminates in a projecting midrib destitute of cellular covering, and this again terminates in a small pouch or pitcher. Somewhat similar variations may be found in ferns, especially Scolopendrium vulgare.

Instead of the pouch there is formed sometimes in the plant last mentioned a supplementary four-lobed lamina, the four lobes being in two different planes, and diverging from the midrib, so that the section would resemble [symbol: Sideways X], the point of intersection of the x representing the position of the midrib. This four-winged lamina is thus very similar to the four-winged filaments described and figured at p. 289, and to the leaf-like anther of Jatropha described by M. Müller, p. 255.

Cornute leaves (Folia cornuta).—The condition to which this term applies is that in which the midrib, after running for a certain distance, generally nearly to the point of the leaf, suddenly projects, often in a plane different from that of the leaf, and thus forms a small spine-like out-growth. Should this happen to be terminated by a second laminar portion, an interrupted leaf would be formed. In Scolopendrium vulgare and other ferns this condition has been noticed, as also in some of the varieties of Codiæum variegatum already referred to.

Flattening.—There are some plants whose stem or branches, instead of assuming the ordinary cylindrical form, are compressed or flattened; such are some species of Epiphyllum, Coccoloba, Bauhinia, &c. The same thing occurs in the leaf-like branches of Ruscus, the flower-stalks of Xylophylla, Phyllanthus, Pterisanthes. Martins proposes to apply the word 'cladodium' to such expansions, just as the term phyllodium is applied to the similar dilatation of the leaf-stalks. If we exclude instances of fasciation, i.e. where several branches are fused together and flattened, we must admit that this flattening does not occur very often as a teratological appearance.

Mr. Rennie figures and describes a root of a tree which had become greatly flattened in its passage between the stones at the bottom of a stream, and had become, as it were, moulded to the stones with which it came into contact.[364]

The spadix of Arum, as also of the cocoa-nut palm, has been observed flattened out, apparently without increase in the number of organs.

When the blade of the leaf is suppressed it often happens that the stalk of the leaf is flattened, as it were, by compensation, and the petiole has then much the appearance of a flat ribbon (phyllode). This happens constantly in certain species of Acacia, Oxalis, &c., and has been attributed, but doubtless erroneously, to the fusion of the leaflets in an early state of development and in the position of rest.[365]

In some water plants, as Sagittaria, Alisma, Potamogeton, &c., the leaf-stalks are apt to get flattened out into ribbon-like bodies; and Olivier has figured and described a Cyclamen, called by him C. linearifolium, in which, owing to the suppression of the lamina, the petiole had become dilated into a ribbon-like expansion—déformation rubanée of Moquin.