Читать книгу Vegetable Teratology - Maxwell T. Masters - Страница 18
ОглавлениеFig. 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 illustrations might be given.
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 Coniferæ, 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 europæus dissectus.
Chelidonium majus laciniatum!
Glaucium luteum.
Brassica oleracea!
Tilia parvifolia laciniata.asplenifolia!
Acer platanoides laciniatum.crispum.
Æsculus 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.
Cratægus Oxyacantha laciniata.quercifolia!
Ribes nigrum.
Sambucus nigra laciniata!racemosa laciniata.
Dipsacus fullonum.
Scabiosa atropurpurea!
Symphoricarpus racemosus.
Helianthus sp.!
Lonicera Periclymenum quercifolia!
Syringa persica laciniata!
Syringa vulgaris!
Nerium Oleander!
Lamium purpureum.album!
Salvia officinalis.
Solanum Dulcamara!
Fraxinus excelsior crispa.
Veronica austriaca.
Polemonium cæruleum.
Juglans regia laciniata!heterophylla.filicifolia.
Anemiopsis californica.
Chenopodium Quinoa.
Ulmus americana incisa.
Fagus sylvatica heterophylla!laciniata!aspleniifolia!incisa.salicifolia!
Mercurialis perennis.
Urtica dioica.
Quercus Cerris laciniata!pubescens filicina.
Betula populifolia laciniata.alba dalecarlica.
Alnus incana laciniata!glutinosa laciniata!quercifolia.oxyacanthifolia.
Corylus Avellana heterophylla!laciniata!urticifolia.
Carpinus Betulus incisa!quercifolia.heterophylla.
Castanea vesca heterophylla.quercifolia.incisa.
Populus alba acerifolia.palmata.quercifolia.balsamifera.
Orchis sambucina.
Arum maculatum.
Filices sp. pl.
See also Schlechtendal, 'Bot. Zeit.,' tom. xiii, p. 823. A. Braun, loc. supra citat. For Ferns too numerous for insertion, see Moore, 'Nature-Printed Ferns,' 8vo ed., 2 vols. Clos, 'Mém. Acad. Toulouse,' 1862, p. 51.
Fission of the petals, &c.—The floral leaves are subject to a similar process of cleavage to that which has just been mentioned as taking place in the leaves. This, indeed, occurs very often as a normal occurrence as in the petals of mignonette (Reseda), or those of Alsine media and many other plants. Here, however, we have only to allude to those instances in which the cleavage occurs in flowers whose sepals or petals are usually entire. Under this category Moquin mentions a petal of Brassica oleracea completely split into two. Linné in his 'Flora Lapponica' (pp. 145 and 164) mentions quadrifid petals of Lychnis dioica, and much divided petals of Rubus arcticus. Among other plants subject to this division of sepals or petals may be mentioned as having come within the writer's personal observation, Ranunculus Lingua, R. acris, Papaver somniferum, and others of this genus, Saponaria sp., Dianthus, Narcissus, &c.
In some of the garden varieties of Cyclamen the corolla looks at first sight as if double, and the plan of the flower is oblong or elliptical, instead of circular. In these flowers each lobe of the corolla is divided almost to the base into two lobes, so that there appear to be ten lobes to the corolla instead of five, as usual. The stamens are normal in form and number in these flowers.
In the paroquet tulips of gardeners the segments of the perianth are deeply and irregularly gashed, the segments occasionally becoming rolled up and their margins coherent so as to form little tubular spurs. I have also noticed the segments of the perianth in Crocus and Colchicum deeply cleft, so much so sometimes, as to equal in this particular the stigmas. In the flowers of a species of Oncidium, communicated to me by Mr. Currey, the lip was divided into three segments perfectly distinct one from the other, but confluent with the column; the two side pieces had callosities at the upper edge close to the base, the central piece had a similar wartlike process in its centre. In these flowers the ovary, the stigma, and the anther were all in a rudimentary condition. Some verbenas raised by Mr. Wills offer a curious illustration of this condition. It will be remembered that some of the lobes or petals of a verbena are normally divided at the base to a slight degree, but in the flowers in question this is carried to such an extent that the enlarged lobes are pushed into the centre of the flower and simulate, at a first glance, a distinct and separate organ, though in reality it is but an enlargement of what occurs normally.[74]
Fig. 29.—Flower of Oncidium sp. seen from the back. The lip is divided into three unequal segments.
Moquin mentions having seen the stamens of Matthiola incana and Silene conica completely divided, each section bearing half an anther, exactly as happens in Polygalaceæ. In tulips and lilies the same author mentions division of the anther only, the filament remaining entire, as happens naturally in many species of Vaccinium.
A division of the individual carpels occurs very frequently when those organs become more or less leafy, as in Trifolium repens, and other plants to be hereafter mentioned.
The instances given in this chapter have all been cases wherein the division or the accessory growth has taken place in one plane only and that plane the same as that of the affected organ, but there are other examples, probably equally due to fissiparous division, where the new growth is either parallel to, or even at angle with the primary organ. Of such nature are some of those instances wherein two leaves appear to be placed back to back. These partake of the nature of excrescences or of exaggerated developments, and hence will be more fully treated of under the head of hypertrophy. It must be remembered that in some of these cases the fission may be a resumption of characters proper to the species under natural conditions, but lost by cultivation or otherwise. Thus, Mr. Buckman accounts for "finger-and-toe" in root-crops on the principle of reversion to the wild form.
