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. Inst.i.t. Amsterdam,' _Lilium_.

Schlechtendal, 'Bot. Zeit.,' xiv, p. 69, et v, p. 66. De Candolle, 'Organ. Veget., t. i, p. 155, tab. x.x.xvi, _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 _Alstroemeria_ it occurs normally, as also in some gra.s.ses. In the variety _annularis_ of _Salix babylonica_ the leaf is constantly coiled round spirally. A similar contortion occurs in a variety of _Codiaeum 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]

=Advent.i.tious tendrils.=--Under ordinary circ.u.mstances 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 cuc.u.mber, while Mr. Holland ('Science Gossip,' 1865, p. 105) mentions a case in which one of the p.r.i.c.kles on the fruit of a cuc.u.mber had grown out into a tendril.

In _Cobaea 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 _Pa.s.sifloraceae_.

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 ma.s.ses, 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.

[Ill.u.s.tration: FIG. 175.--Interrupted growth of Radish (from the 'American Agriculturist.')]

[Ill.u.s.tration: 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 _Codiaeum variegatum_ the leaves resemble those of _Nepenthes_, as the basal portion is broad, and terminates in a projecting midrib dest.i.tute 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. Muller, 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 _Codiaeum variegatum_ already referred to.

=Flattening.=--There are some plants whose stem or branches, instead of a.s.suming 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 pa.s.sage 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--deformation rubanee of Moquin.

FOOTNOTES:

[350] Moore, 'Nature Printed Ferns,' 8vo edition, vol. ii, p. 154, et p.

173.

[351] 'Flora (B. Z.),' 1821, vol. iv, p. 717, c. tab.

[352] Chavannes, 'Mon. Antirrh.'

[353] 'Bull. Soc. Bot. France,' t. vii, 1860, p. 877.

[354] Ibid., t. iv, 1857, p. 759.

[355] Jaeger, "De monstrosa folii _Phoenicis dactyliferae_ conformatione a Goetheo olim observata," 'Act. Acad. Leop. Car. Nat.

Cur.,' vol. xvii, suppl., p. 293, c. tab. color. iv.

[356] See Goethe, 'Ueber die spiral Tendenz.'

[357] See Darwin "On Climbing Plants," 'Journ. Linn. Soc. Botany,' vol.

ix, p. 5.

[358] 'Ephem. Nat. Cur.,' dec. 2, ann. 1, 1683, p. 68, fig. 14.

[359] 'Ann. des Scienc. Nat.,' third series, vol. i, 1844, p. 292.

[360] 'Flora' Feb. 4, 1858, p. 69, tab. ii, f. 3, and also 'Flora,'

1860, p. 737, tab. vii, f. 9.

[361] 'Bull. Acad, Belg.,' t. xvii, p. 196, "Lobelia," p. 53, c. tab.

[362] Moore, 'Nature-printed Ferns,' 8vo edition, vol. ii, p. 183.

[363] 'Bull. Soc. Bot. Fr.,' 1860, vol. vii, p. 461. See also Naudin, 'Ann. Sc. Nat.,' 4 ser., t. iv, p. 5. Clos, 'Bull. Soc. Bot. Fr.,' t.

iii, p. 546.

[364] London's 'Magazine Nat. Hist.,' vol. ii, p. 463.

[365] C. Morren, 'Bull. Acad. Belg.,' 1852, t. xix, part iii, p. 444.

CHAPTER II.

POLYMORPHY.

Usually the several organs of the same individual plant do not differ to any great extent one from another. One adult leaf has nearly the same appearance and dimensions as another; one flower resembles very closely another flower of the same age and so on. Nevertheless it occasionally happens that there is a very considerable difference in form in the same organs, not only at different times, but it may also be at the same time. Descriptive botanists recognise this occurrence in the case of leaves, and apply the epithet heterophyllous to plants possessed of these variable foliar characters. In the case of the flower, where similar diversity of form occasionally exists, the term dimorphism is used.

As these phenomena appear constantly in particular plants, they are hardly to be looked on, under such circ.u.mstances, as abnormal, but where they occur in plants not usually polymorphic, they may be considered as coming within the scope of teratology.