[57] 'Ann. Sc. Nat.,' t. xix, 1843, p. 141, tab. iv.

[58] 'Ann. Nat. Hist.,' ser. 2, vol. ix, tab. xvi. 'Phytologist,' 1857.

p. 352, &c.

[59] Quoted from the 'Revue Hortic.' in 'Gard. Chron.,' 1866, p. 386.

[60] Senebier, 'Phys Veget.,' t. iv, p. 426. The same author also cites Romer as having found two plants of _Ranunculus_, from the stem of which emerged a daisy. As it is not an uncommon practice to stick a daisy on a b.u.t.tercup, it is to be hoped no hoax was played off on M. Romer.

[61] 'El. Ter. Veg.,' p. 289.

[62] An instance of this kind is cited in Dr. Robson's memoir of the late Charles Waterton, from which it appears that two trees, a spruce fir and an elm, were originally planted side by side, and had been annually twisted round each other, so that they had in places grown one into the other, with the result of stunting the growth of both trees, thus ill.u.s.trating, according to the opinion of the eccentric naturalist above cited, the incongruous union of Church and State!

[63] See Daubeny, 'Lectures on Roman Husbandry,' p. 156.

[64] A. P. De Candolle, 'Organ Veget.,' t. ii, p. 72, tab. liv, fig. 1.

[65] 'Bull. Acad. Belg.,' t. xx, part i, 1852, p. 43.

PART II.

INDEPENDENCE OR SEPARATION OF ORGANS.

Under this head are included all those instances wherein organs usually entire, or more or less united, are, or appear to be, split or disunited. It thus includes such cases as the division of an ordinarily entire leaf into a lobed or part.i.te one, as well as those characterised by the separation of organs usually joined together. Union, as has been stated in a previous chapter, is the result either of persistent integrity or of a junction of originally separate organs, after their formation; so in like manner, the separation or disjunction of parts may arise from the absence of that process of union which is habitual in some cases, or from an actual _bona fide_ separation of parts originally united together. In the former case, the isolation of parts arises from arrest of development, while in the latter it is due rather to luxuriant growth. A knowledge, as well of the ordinary as of the unusual course, of development in any particular flower is thus required in order to ascertain with accuracy the true nature of the separation of parts. The late Professor Morren[66] proposed the general term Monosy ([Greek: monosis]) for all these cases of abnormal isolation, subdividing the group into two, as follows--1, Adesmy ([Greek: a-desmos]), including those cases where the separation is congenital; and 2, Dialysis ([Greek: dialyo]), comprising those instances where the isolation is truly a result of the separation of parts previously joined together. Adesmy, moreover, was by the Belgian savant said to be h.o.m.ologous when it occurred between members of the same whorl, _e.g._ between the sepals of an ordinary monosepalous calyx, or heterologous when the separation took place between members of different whorls, as when the calyx is detached from the ovary, &c. The former case would thus be the converse of cohesion, the latter of adhesion.

To the adoption of these words there is this great objection, that we can but rarely, in the present state of our knowledge, tell in which group any particular ill.u.s.tration should be placed.

The terms adopted in the present work are, for the most part, not necessarily intended to convey any idea as to the organogenetic history of the parts affected. Where a single organ, that is usually entire, becomes divided the term Fission is used; in cases where parts of the same whorl become isolated, the word Dialysis is employed, and in the same sense in which it is generally used by descriptive botanists, and where the various whorls become detached one from the other, the occurrence is distinguished by the application of the term Solution.

FOOTNOTES:

[66] 'Bull. Acad. Belg.,' t. xix, part iii, 1852, p. 315.

CHAPTER I.

FISSION.

When an organ becomes divided it receives at the hands of descriptive botanists the appellations cleft, part.i.te, or sect, according to the depth of the division; hence in considering the teratological instances of this nature, the term fission has suggested itself as an appropriate one to be applied to the subdivision of an habitually entire or undivided organ. It thus corresponds pretty nearly in its application with the term Chorisis or "dedoublement," or with the "disjonctions qui divisent les organes" of Moquin-Tandon.[67] It is usually, but not always, a concomitant with hypertrophy, and dependent on luxuriance of growth.

It must be understood therefore that the term, as generally applied, does not so much indicate the cleavage of a persistent organ, as it does the formation and development of two or more growing points instead of one, whence results a branching or forking (di-tri-chotomy) of the affected organ. In some instances it seems rather to be due to the relative deficiency of cellular, as contrasted with fibro-vascular tissue.

=Fission of axile organs.=--This condition is scarcely to be distinguished from multiplication of the axile organs (which see). A little attention, however, will generally show whether the unusual number of branches is a consequence of the development of a large number of distinct shoots, as happens, for instance, when a tree is pollarded, or of a division of one. M. Fournier[68] gives as an ill.u.s.tration the case of a specimen of _Ruscus aculeatus_ in which there occurred a division of the foliaceous branches into two segments, reaching as far as the insertion of the flower, but no further. He also mentions lateral cleavage effected by a notching of the margin, the notch being anterior to the flowers and always directed towards their insertion. In the allied genus _Danae_, Webb, 'Phyt. Canar.,' p. 320, describes the fascicles of flowers as in "crenulis brevibus ad marginem ramulorum dispositis." Sometimes, on the other hand, _Danae_ has a fascicle of flowers inserted on the middle of the upper surface, as in _Ruscus_.

Wigand mentions an instance in _Digitalis lutea_, where the upper part of the stem was divided into six or seven racemes; possibly this was a case of fasciation, but such a division of the inflorescence is by no means uncommon in the spicate species of _Veronica_. I have also seen it in _Plantago lanceolata_, _Reseda luteola_, _Campanula medium_, _Epacris impressa_, and a bifurcation of the axis of the spikelet within the outer glumes in _Lolium perenne_[69] and _Anthoxanthum odoratum_. In the Kew Museum is preserved a cone of _Abies excelsa_,[70] dividing into two divisions, each bearing bracts and scales. A similar thing frequently occurs in the male catkins of _Cedrus Libani_ (fig. 25).

[Ill.u.s.tration: FIG. 25.--Bifurcated male inflorescence, _Cedrus Libani_.]

This subdivision of axial organs is not unfrequently the result of some injury or mutilation, thus Duval Jouve alludes to the frequency with which branched stems are produced in the various species of _Equisetum_, as a consequence of injuries to the main stem, but this is rather to be considered as a multiplication of parts than as a subdivision of one.

[Ill.u.s.tration: FIG. 26.--Bifurcated leaf of _Lamium alb.u.m_, &c.]

=Fission of foliar organs.=--Many leaves exhibit constantly the process of fission, such as the _Salisburia adiantifolia_, and which is due perhaps as much to the absence or relatively small proportion of cellular as compared with vascular tissue, as to absolute fission. In the same way we have laciniated leaves of the Persian lilac, _Syringa persica_, and Moquin mentions instances in a species of _Mercurialis_ in which the leaves were deeply slashed. In _Chenopodium Quinoa_ the leaves were so numerous and the clefts so deep, that the species was hardly recognisable, while on a branch of _Rhus Cotinus_ observed by De Candolle the lobes were so narrow and so fine as to give the plant the aspect of an _Umbellifer_. Wigand ('Flora,' 1856, p. 706) speaks of the leaves of _Dipsacus fullonum_ with bi-part.i.te leaves; Moquin mentions the occurrence of a leaf of an oleander bi-lobed at the summit, so as to give the appearance of a fusion of two leaves. Steinheil has recorded an instance in _Scabiosa atropurpurea_ in which one of the stem leaves presented the following peculiarities. It was simple below, but divided above into two equal lobes, provided each with a median nerve.[71]

Steinheil has also recorded a _Cerastium_ in which one of the leaves was provided with two midribs; above this leaf was a group of ternate leaves. I have seen similar instances in the common Elm, _Ulmus campestris_, and also in the common nettle, _Urtica dioica_, the leaves of which latter thus resembled those of _Urtica biloba_, which are habitually bilobed at the summit. M. Clos[72] mentions an instance where the terminal leaf and first bract of _Orchis sambucina_ were divided into two segments. The same author also mentions the leaves of _Anemiopsis californica_, which were divided in their upper halves each into two lobes--also leaves of a lentil springing from a fasciated stem and completely divided into two segments, but with only a single bud in the axil. The axillary branches in like manner showed traces of cleavage. Fig. 26 represents a case of this kind in _Lamium alb.u.m_, conjoined with suppression of the flowers on one side of the stem. I have also in my herbarium a leaf of _Arum maculatum_, with a stalk single at the base, but dividing into two separate stalks, each bearing a hastate lamina, the form of which is so perfect that were it not from the venation of the sheath it would be considered that there was here a union of two leaves rather than a bifurcation of one. A garden Pelargonium presented the same appearance.

[Ill.u.s.tration: FIG. 27.--Bifurcated leaf of _Pelargonium_.]

Fern fronds are particularly liable to this kind of subdivision, and they exhibit it in almost every degree, from a simple bifurcation of the frond to the formation of large tufts of small lobes all formed on the same plan by the repeated forking of the pinnules. These may be considered as cases of hypertrophy.

Moquin-Tandon, at a meeting of the Botanical Society of France (April 3rd, 1858) exhibited a leaf of _Cerasus Lauro-Cerasus_ divided in such a manner as to resemble a leaf of _Citrus_ or of _Phyllarthron_. In this case, therefore, the disunion must have taken place laterally, and not from apex towards base, as is most common. The leaves of the common horse-radish, _Cochlearia Armoracia_, are very subject to this pinnated subdivision of the margin, and numerous other ill.u.s.trations might be given.

[Ill.u.s.tration: FIG. 28.--Bifurcated frond, _Scolopendrium vulgare_.]

A. Braun describes a singular case in a leaf of _Irina glabra_ wherein the blade of the leaf on one side was deeply and irregularly laciniated, the other side remaining entire. (Verhandl., d. 35, Naturforscherversammlung, tab. 3.) Laciniate varieties of plants are of frequent occurrence in gardens where they are often cultivated for their beauty or singularity; thus, there are laciniated alders, fern-leaved beeches and limes, oak-leaved laburnums, &c. A list of several of these is subjoined. A similar fission takes place constantly in the cotyledons of some plants, sometimes, as in _Coniferae_, to such an extent as to give an appearance as if there were several cotyledons.[73]

It is not always easy to recognise, at a first glance, whether the division be the result of disunion or of an incomplete union of two leaves, but we may be guided by the number of leaves in the cycle or the whorl. The number is complete in cases of partial disjunction, while in cases of fusion it is incomplete. Again, in instances of disjunction, there is only one point of origin, but, when two leaves are grafted together, two such points may generally be detected at the base of the leaf, or a transverse section of the leaf-stalk will show indications of fusion. The number and position of the midribs will also serve as a guide, as in cases of fusion there are generally two or more midribs, according to the number of fused leaves; but as Moquin well remarks, this latter character cannot be always depended upon, for the median nerve may divide without any corresponding separation of the cellular portions of the leaf. The author just quoted cites examples of this kind in _Cardamine pratensis_, _Hedera Helix_, _Plantago major_, _Geranium nodosum_.

The following list of plants commonly producing leaves that are cleft or divided, to a greater extent than is usual in the species, is mainly taken from one given by Schlechtendal, 'Bot. Zeit.,' 1844, p. 441, with additions from other sources. The ! indicates that the author has himself met with the deviation in question. Many are cultivated as garden varieties under the names here given.

Trollius europaeus dissectus.

Chelidonium majus laciniatum!

Glaucium luteum.

Bra.s.sica oleracea!

Tilia parvifolia laciniata.

asplenifolia!

Acer platanoides laciniatum.

crispum.

aesculus Hippocastanum incisum!

asplenifolium.

Vitis vinifera apiifolia!

laciniosa.

Ilex Aquifolium!

Rhus Toxicodendron quercifolium.

Cotinus.

Ervum Lens.

Cytisus Laburnum quercifolium!

incisum.

Rubus fraticosus laciniatus!

Pyrcis communis.

Cerasus Lauro-cerasus.

Apium graveolens!

Pimpinella magna.

Saxifraga.

Crataegus Oxyacantha laciniata.