Vegetable Teratology Part 2

[Ill.u.s.tration: FIG. 4.--Fasciation in _Asparagus_.]

[Ill.u.s.tration: FIG. 5.--Fasciated branch of _Pinus Pinaster_.]

Very generally the surface is striated by the prominence of the woody fibres which, running parallel for a time, converge or diverge at the summit according to the shape of the branch. If the rate of growth be equal, or nearly so, on both sides, the stem retains its straight direction, but it more generally happens that the growth on one side is more rapid and more vigorous than on the other, and hence arises that curvature of the fasciated branch so commonly met with, _e.g._ in the ash (_Fraxinus_), wherein it has been likened to a shepherd's crook. It is probable that almost any plant may present this change. It occurs alike in herbaceous and in woody plants, originating in the latter case while the branches are still soft. It may be remarked that, in the case of herbaceous plants, the fasciation always affects the princ.i.p.al stem, while, on the other hand, in the case of trees and shrubs the deformity occurs most frequently in the branches; thus, while in the former it may be said that the whole of the stem is more or less affected, in the latter it is rare to see more than one or two branches of the same tree thus deformed. It is a common thing for the fasciated branch to divide at the summit into a number of subdivisions. These latter may be deformed like the parent branch, or they may resume the ordinary aspect of the twigs.

[Ill.u.s.tration: FIG. 6.--Fasciation and spiral torsion in the stem of _Asparagus_.]

Sometimes the flattened stem is dest.i.tute of buds, at other times, these organs are scattered irregularly over its surface or are crowded together in a sort of crest along the apex. When, as often happens, the deformity is accompanied with a twisting of the branch spirally, the buds may be placed irregularly, or in other cases along the free edge of the spiral curve. In a specimen of _Bupleurum falcatum_ mentioned by Moquin the spiral arrangement of the leaves was replaced by a series of perfect whorls, each consisting of five, six, seven, or eight segments, and there was a flower-stalk in the axil of each leaf.

When flowers are borne on these fasciated stems they are generally altered in structure; sometimes the thalamus itself becomes more or less fasciated or flattened, and the different organs of the flower are arranged on an elliptical axis. A case of this nature is described by Schlechtendal ('Bot. Zeit.,' 1857, p. 880), in _Cytisus nigricans_, and M. Moquin-Tandon describes an instance in the vine in one flower of which sepals, petals, stamens, and ovary were abortive, while the receptacle was hypertrophied and fasciated, and bore on its surface a few advent.i.tious buds.[11] The pedicels of _Streptocarpus Rexii_ have also been observed in a fasciated state.[12]

It has been occasionally observed that the fasciated condition is hereditary; thus, Moquin relates that some seeds of a fasciated _Cirsium_ reproduced the same condition in the seedlings,[13] while a similar tendency is inherited in the case of the c.o.c.ks...o...b..(_Celosia_).

With reference to the nature of the deformity in question there is a difference of opinion; while most authors consider it to be due to the causes before mentioned, Moquin was of opinion that fasciation was due to a flattening of a single stem or branch. Linnaeus, on the other hand, considered such stems to be the result of the formation of an unusual number of buds, the shoots resulting from which became coherent as growth proceeded:--"_Fasciata dici solet planta c.u.m plures caules connasc.u.n.tur, ut unus ex plurimis instar fasciae evadat et compressus_"

(Linn., 'Phil. Bot.,' 274). A similar opinion was held by J. D. Major in a singular book ent.i.tled 'De Planta, Monstrosa, Gottorpiensi,'

Schleswig, 1665, wherein the stem of a _Chrysanthemum_ is depicted in the fasciated condition.

[Ill.u.s.tration: FIG. 7.--Fasciation in the scape of the Dandelion (_Leontodon Taraxac.u.m_).]

The striae, which these stems almost invariably present, exhibit the lines of junction, and the spiral or other curvatures and contraction, which are so often met with, may be accounted for by the unequal growth of one portion of the stem as contrasted with that of another. Against this view Moquin cites the instances of one-stemmed plants, such as _Androsace maxima_, but, on the other hand, those herbaceous plants having usually but a single stem not unfrequently produce several which may remain distinct, but not uncommonly become united together. Prof.

Hincks[14] cites cases of this kind in _Primula vulgaris_, _Hieracium aureum_, and _Ranunculus bulbosus_. I have myself met with several cases of the kind in _Primula veris_, in the Polyanthus, in the Daisy, and in the _Leontodon Taraxac.u.m_, in which latter a fusion of two or more flower-stems bearing at the top a composite flower, and made up of two, three, four, or more flowers combined together, and containing all the organs that would be present in the same flowers if separate, is very common.

Moquin's second objection is founded upon the fact that, in certain fasciated stems, the branches are not increased in number or altered in arrangement from what is usual; but however true this may be in particular cases, it is quite certain that in the majority of instances a large increase in the number of leaves and buds is a prominent characteristic of fasciated stems.

Another argument used by the distinguished French botanist to show that fasciated stems are not due to cohesion of two or more stems, is founded on the fact that a transverse section of a fasciated stem generally shows an elliptical outline with but a single central ca.n.a.l. On the other hand, if two branches become united and a transverse section be made, the form of the cut surface would be more or less like that of the figure 8[Symbol: 8 turned 90], although in old stems this may give place to an elliptical outline, but even then traces of two medullary ca.n.a.ls may be found. This argument is very deceptive, for the appearance of the transverse section must depend, not only on the intimacy of their union, but also on the internal structure of the stems themselves. When two flowers cohere without much pressure they exhibit uniting circles somewhat resembling the figure of 8[Symbol: 8 turned 90], but when more completely combined they have an outline of a very elongated figure, and something similar is to be expected in herbaceous stems. Even the elongated pith of a transversely cut, woody, fasciated stem only marks the intimate union of several branches, and Prof. Hincks, whose views the writer entirely shares, has noticed instances of the union of two, and of only two, stems where the internal appearance was the same as in other fasciations.

Moquin, moreover, raises the objection that it is unlikely that several branches should become united lengthwise in one plane only, and, further, that in the greater number of fasciations all the other branches which should be present are to be found--not one is wanting, not one has disappeared, as might have been antic.i.p.ated had fusion taken place. In raising this objection, Moquin seems not sufficiently to have considered the circ.u.mstance that the buds in these cases are in one plane from the first, and are all about equal in point of age and size.

The last objection that Moquin raises to the opinion that fasciation is the result of a grafting process is, that in such a case, examples should be found wherein the branches are incompletely fused, and where on a transverse section traces of the medullary ca.n.a.ls belonging to each branch should be visible. The arrangement of leaves or buds on the surface should also in such a case indicate a fusion of several spiral cycles or whorls. To this it may be replied that such cases are met with very frequently indeed. A figure is given by De Candolle[15] of a stem of _Spartium junceum_ having several branches only imperfectly fasciated.

Fasciated stems, then, seem to be best explained, as is stated by Prof.

Hincks, "on the principle of adhesion arising in cases where from superabundant nourishment, especially if accompanied by some check or injury, numerous buds have been produced in close proximity, and the supposition that these growths are produced by the dilatation of a single stem is founded on a false a.n.a.logy between fasciated stems and certain other anomalous growths."

It will not, of course, be forgotten that this fasciated condition occurs so frequently in some plants as almost to const.i.tute their natural state, _e.g._ _Sedum cristatum_, _Celosia_, &c. This condition may be induced by the art of the gardener--"_Fit idem arte, si plures caules enascentes cogantur penetrare coarctatum spatium et parturiri tanquam ex angusto utero, sic saepe in Ranunculo, Beta, Asparago, Hesperide Pinu, Celosia, Tragopogone, Scorzonera Cotula foetida_,"

Linnaeus op. cit.

Plot, in his 'History of Oxfords.h.i.+re,' considers fasciation to arise from the ascent of too much nourishment for one stalk and not enough for two, "which accident of plants," says Plot, the German virtuosi ('Misc.

Curios. Med. Physic. Acad. Nat. Cur.,' Ann. i, Observ. 102,) "think only to happen after hard and late winters, by reason whereof, indeed, the sap, being restrained somewhat longer than ordinary, upon sudden thaws may probably be sent up more forcibly, and so produce these fasciated stalks, whereas the natural and graduated ascent would have produced them but single." Prof. Hincks' explanation is, however, more near to the truth, and his opinion is borne out by the frequency with which this change is met with in certain plants which are frequently forced on during their growth, as lettuce, asparagus, endive, &c., all of which are very subject to this change. In the 'Transactions of the Horticultural Society of London,' vol. iv, p. 321, Mr. Knight gives an account of the cultivation of the c.o.c.ks...o...b.. so as to ensure the production of the very large flower-stalks for which this plant is admired. The princ.i.p.al points in the culture were the application of a large quant.i.ty of stimulating manure and the maintenance of a high temperature. One of them so grown measured eighteen inches in width.

The list which is appended is intended to show those plants in which fasciation has been most frequently observed. It makes no pretension to be complete, but is sufficiently so for the purpose indicated: the *

denotes the especial frequency of the change in question; the !

indicates that the writer has himself seen the plant, so marked, affected in this way. The remainder have been copied from various sources.

EXOGENS.

[Greek: alpha]. _Herbaceous._

Ranunculus tripart.i.tus.

* bulbosus!

Philonotis.

Delphinium elatum.

* sp.!

Hesperis matronalis.

*Cheiranthus Cheiri!

*Matthiola incana!

*Bra.s.sica oleracea! var. pl. inflor.

Linum usitatissimum!

Althaea rosea!

Lavatera trimestris.

Geranii sp.

Tropaeolum majus!

Viola odorata inflor.!

Reseda odorata!

Fragaria vesca.

Ervum lens.

Trifolium resupinatum.

repens!

pratense!

Saxifraga mutata.

irrigua.

Bupleurum falcatum.

Bunium flexuosum.

*Sedum reflexum!

cristatum!

Epilobium augustifolium!

Momordica Elaterium!

Gaura biennis.

Cotula foetida.

Barkhausia taraxacifolia.

Carlina vulgaris!

Apargia autumnalis.

*Leontodon Taraxac.u.m inflor.!

Centaurea Scabiosa.

*Cichorium Intybus!

Hieracium Pilosella.

aureum.

umbellatum.

*Chrysanthemum Leucanthemum.

indic.u.m!

Anthemis n.o.bilis.

arvensis.

Cirsium lanceolatum.

Conyza squarrosa!

Inula dysenterica!

Tragopogon porrifolium.

Cnicus pal.u.s.tris.

Carduus arvensis!

Helianthus tuberosus!