Cuc.u.mis!

Campanula!

Sambucus!

*Primula!

Anagallis!

Lycium.

Solanum.

Symphytum.

Syringa!

Linaria.

Chenopodium.

*Paris!

Convallaria!

Allium.

*Lilium!

*Tulipa!

Ornithogalum.

*Gagea!

Tradescantia!

Orchideae, sp. pl.!

=Increased number of ovules or seeds.=--This appears not to be of very frequent occurrence, at least in those plants where the number of these organs is normally small; where, as in _Primula_, the ovules and seeds are produced in large quant.i.ties, it is not practicable to ascertain whether the number be augmented or not in any particular case. Very probably, the attachment or source of origin of the ovules determines, in some measure, their number. Thus, in the case of marginal placentation the number must be limited by the narrow s.p.a.ce from which they proceed, whereas in parietal and free central placentation the ovules are generally numerous. In the latter case, however, it will be remembered that solitary ovules are not rare. An increased number of ovules is generally remarked in conjunction with some other change, such as a foliaceous condition of the carpel, in which the margins are disunited. In such cases the ovules may occupy the margin or may be placed a short distance within it, as in the case of some open carpels of _Ranunculus Ficaria_,[417] and in which two ovules were borne in shallow depressions on the upper or inner surface of the open carpel and supplied with vascular cords from the central bundle or midrib. The outer coating of the ovule here contained barred or spiral fusiform vessels derived from the source just indicated.

In the very common cases where the pistil of _Trifolium repens_ becomes foliaceous (see Frondescence), the outer ovules are generally two or more instead of being solitary. So, also, in the Rose with polliniferous ovules (see p. 274). Among _Umbelliferae_ affected with frondescence of the pistil a similar increase in the number of ovules takes place. It will be borne in mind that in most, if not all, these cases the structure of the ovule is itself imperfect.[418]

What are called in popular parlance double almonds or double nuts (_Corylus_) are cases where two seeds are developed in place of one.

In the 'Revue Horticole,' 1867, p. 382, mention is made of a bush which produces these double nuts each year--in fact, it never produces any single-seeded fruit. The plant was a chance seedling, perhaps itself the offspring of a double-seeded parent. It would be interesting to observe if the character be retained by the original plant, and whether it can be perpetuated by seed or by grafting.

It is necessary to distinguish in the case of the nut between additional seeds or ovules, as just described, and the double, triple, or fourfold nuts that are occasionally met with, and which are the result either of actual multiplication of the carpels or of the continued development of some of the carpels which, under ordinary circ.u.mstances cease to grow (see _ante_, p. 364). In the case of a ripe nut with two seeds it might be impossible to tell whether the advent.i.tious seed were the product of multiplication, or whether it belonged, in the first instance, to the same carpel as that producing the fellow-seed, or to a different and now obliterated ovary. In all probability, however, the second seed would be accounted for by the development of two seeds in one carpellary cavity.

There is still another condition occasionally met with in the almond, and which must be discriminated from the more common multiplication of the seed, and which is the multiplication of the embryos within the seed, and which furnishes the subject of the succeeding paragraph.

=Increased number of embryos.=--A ripe seed usually contains but a single embryo, although in the ovular state preparation is commonly made for more; and, indeed, in certain natural orders plurality of embryos in the same seed does occur, as in _Cycadeae_ and _Coniferae_. In the seeds of the orange (_Citrus_), in those of some _Euphorbiaceae_, &c., there are frequently two or more additional embryos. A similar occurrence has been recorded in the mango, for a specimen of which I am indebted to the Rev. Mr. Parish, of Moulmein.[419]

Plurality of embryos has also been observed in--

Rapha.n.u.s sativus.

*Citrus Aurantium!

Diosma, sp.

Hyperic.u.m perforatum.

Triphasia aurantiaca.

*aesculus Hippocastanum!

Euonymus latifolius.

*Mangifera indica!

Eugenia Jambos.

Amygdalus vulgaris!

Vicia, sp.

Ca.s.sia, sp.

*Visc.u.m alb.u.m!

Daucus Carota.

Ardisia serrulata!

Cynanchum nigrum.

fuscatum.

Euphorbia rosea.

Coelebogyne ilicifolia.

Allium fragrans.

Funckia, sp.

Carex maritima.

Zea Mays.

See Schauer's translation of Moquin-Tandon, 'El. Terat.

Veget.,' p. 245, adnot., and 'Al. Braun Polyembryonie.'

=Increased number of the cotyledons.=--Although the presence of one or of two cotyledons in the embryo is generally accepted as a valuable means of separating flowering plants into two primary groups, yet, like all other means of discrimination, it occasionally fails, and, indeed, almost always requires to be taken in conjunction with some other character. There are cases among flowering plants where the embryo is h.o.m.ogeneous in its structure, there are others in which the number of the cotyledons is more than two. Thus, in some seeds of _Cola ac.u.minata_ the cotyledons vary in number from two to five. I have not been able to ascertain precisely whether this multiplication of the cotyledons is characteristic of all the seeds of particular trees, or whether some only are thus affected. Some fruits that I examined bore out the latter view, as in the same pod were seeds with two, three, and four cotyledons respectively.

I have also seen three cotyledons present in embryo-plants of _Correa_, _Crataegus Oxyacantha_, _Dianthus sinensis_, _Daucus Carota_, _Cerasus Lauro-cerasus_. De Candolle alludes to a case of the kind in the bean, and figures a species of _Solanum_ with three cotyledons.[420] Jaeger alludes to a similar instance in _Apium Petroselinum_;[421] Ehrenberg to one in the marigold (_Calendula_);[422] Reinsch to an a.n.a.logous appearance in the beech (_f.a.gus_), a.s.sociated with a union of the margins of two out of the three cotyledons, and of those of two out of the three leaves next adjacent.[423] This fusion seems frequently to accompany increase in the number of cotyledons. It was so in the _Correa_, and in the _Crataegus_ previously mentioned. Some of these cases may be accounted for by chorisis or by a cleavage of the original cotyledons, as happens, according to Duchartre,[424] in some Coniferae, which he considers to be improperly termed polycotyledonous. Whether this holds good in the Loranths, where (_Nuytsia_, _Psittacanthus_) an appearance of polycotyledony exists, is not stated. In the case of the rue (_Ruta_) figured by M. A. de Jussieu[425] this splitting of one cotyledon into two is sufficiently evident, as is also the case in the sycamore (_Acer pseudo-plata.n.u.s_), seedlings of which may often be met with divided cotyledons.

In other instances a fusion of two embryo plants may give rise to a similar appearance, as in the _Euphorbia_ and _Sinapis_ found by M.

Alph. de Candolle (see _ante_, p. 56).

=Pleiotaxy or multiplication of whorls.=--In the preceding section notice has been taken of the increased number of parts in a single whorl, but an augmentation of the number of distinct whorls is still more frequently met with. Many of the so-called double flowers owe their peculiarity to this condition. The distinction between the two modes in which the parts of the flower are increased in number has been pointed out by Engelmann, Moquin, and others, and the two seem to require distinctive epithets; hence the application of the terms polyphylly and pleiotaxy, as here proposed.

=Pleiotaxy in the bracts.=--An increase in the number of bracts has been met with very constantly in a species of _Maesa_, and in a peculiar variety of carnation, called the wheat-ear carnation.[426] In some of these cases the increase in the number of bracts is attended by a corresponding suppression in the other parts of the flower. Such a condition has been frequently met with in _Gentiana Amarella_, where the bracts are increased in number, coloured purple, and dest.i.tute of any true floral organs. A similar condition exists in some varieties of _Plantago major_ (var. _paniculata_), as has been previously stated, p.

109.

[Ill.u.s.tration: FIG. 187.--Wheat-ear carnation. The appearance is due to the multiplication of the bracts and the suppression of the other parts of the flower.]

It has been noticed also in the common pea, _Pisum sativum_, and M.

Lortet[427] records a case of the kind in _Erica multiflora_, the flowers of which, under ordinary circ.u.mstances, are arranged in cl.u.s.ters, but in this case the pedicels were more closely crowded than usual, and were covered for their whole length with small rose-coloured bracts arranged in irregular whorls, the upper ones sometimes enclosing imperfect flowers. In the 'Gardeners' Chronicle,' 1865, p. 769, is figured a corresponding instance of _Delphinium Consolida_, in which the bracts were greatly increased in number, petaloid, and, at the same time, the central organs of the flower were wholly wanting.

[Ill.u.s.tration: FIG. 188.--_Delphinium Consolida_. Multiplication of bracts at the expense of the other parts of the flower.]

[Ill.u.s.tration: FIG. 189.--Multiplication of bracts, &c., _Pelargonium_.]

In flowers of _Pelargonium_ may occasionally be seen a repet.i.tion of the whorls of bracts, in conjunction with suppression and diminished size of some of the other portions of the flower (fig. 189).

The common foxglove (_Digitalis purpurea_) has likewise occasionally been observed subject to a similar malformation.

_Cornus mas_ and _C. suecica_ sometimes show a triple involucre.[428]

Irmish[429] records an a.n.a.logous case in _Anemone Hepatica_, wherein the involucre was doubled. Similar augmentation occurs in cultivated Anemone. In addition to the plants already mentioned, Engelmann[430]

mentions as having produced bracts in unwonted numbers, _Lythrum Salicaria_, _Plantago major_, _Veronica spicata_, _Echium vulgare_, _Melilotus arvensis_, and _Rubus fruticosus_.

It must here be remarked that this great number of the bracts occurs naturally in such plants as _G.o.doya_, in which the bracts, or, as some consider them, the segments of the calyx, are very numerous, and arranged in several overlapping segments.

In some of the cultivated double varieties of _Nigella_ the finely divided involucral bracts are repeated over and over again, but on a diminished scale, to the exclusion of all the other parts of the flower.

=Pleiotaxy or repet.i.tion of the calyx.=--The true calyx is very seldom affected in this manner, unless such organs as the epicalyx of mallows, _Potentilla_, &c., be considered as really parts of the calyx.

In _Linaria vulgaris_ Roeper observed a calyx consisting of a double series, each of five sepals, in conjunction with other changes.[431] It is also common in double columbines, delphiniums, nigellas, &c.