PART II.

DIMINISHED NUMBER OF ORGANS.

A diminution in the number of parts is generally due to suppression, using that word as the equivalent of non-development. It corresponds thus in meaning with the _Fehlschlagen_ of the Germans, the _avortement complete_ of Moquin and other French writers. It differs from atrophy, or partial abortion, inasmuch as the latter terms apply to instances wherein there has been a partial development, and in which evolution has gone on to a certain extent, but has, from some cause or other, been checked. These cases will be found under the head of diminished size of organs. As the word abortion is used by different authors in different ways, it is the more necessary to be as precise as possible in the application of the term. In the present work abortion is used to apply to cases wherein parts have been formed, but wherein growth has been arrested at a certain stage, and which, therefore, have either remained _in statu quo_, while the surrounding parts have increased, or have, from pressure or other causes, actually diminished in size.

In practice, however, it is not always possible to discriminate between those instances in which there has been a true suppression, an absolute non-development of any particular organ, and those in which it has been formed, and has grown for a time, but has afterwards ceased to do so, and has been gradually obliterated by the pressure exercised by the constantly increasing bulk of adjacent parts, or possibly has become incorporated with them. In the adult flower the appearances are the same, though the causes may have been different.

CHAPTER I.

SUPPRESSION OF AXILE ORGANS.

Absolute suppression of the main axis is tantamount to the non-existence of the plant, so that the terms "acaulescent," "acaulosia," etc, must be considered relatively only, and must be taken to signify an atrophied or diminished size of the stem, arising from the non-development of the internodes.

The absence of lateral branches or divisions of the axis is of frequent occurrence, and is dependent on such causes as the following:--deficient supply of nutriment, position against a wall or other obstacle, close crowding of individual plants, too great or too little light, too rich or too poor a soil, &c.

Probably the absence of the swollen portion below the flower in the case of many proliferous roses, double-flowered apples, as already referred to, may be dependent on the non-development of the extremity of the peduncle or flower-stalk. Thus, in a double-flowered apple recently examined, there was a sort of involucel of five perfect leaves, then five sepals surrounding an equal number of petals, numerous stamens, and five styles, but not a trace of an expanded axis, nor of any portion of the carpels, except the styles. The views taken as to the nature of this and similar malformations must depend on the opinion held as to the nature of inferior pistils, and on the share, if any, that the expanded axis takes in their production. As elsewhere said, the evidence furnished by teratology is conflicting, but there seems little or nothing to invalidate the notion that the end of the flower-stalk and the base of the calyx may, to a varying extent, in different cases, jointly be concerned in the formation of the so-called calyx-tube and of the inferior ovary. Obviously it is not proper to apply to all cases where there is an inferior ovary the same explanation as to how it is brought about.

As these pages are pa.s.sing through the press, M. Casimir de Candolle has published a different explanation as to the nature of the hip of the rose, having been led to his opinion by the conclusion that he has arrived at, that the leaf is to be considered in the light of a flattened branch, whose upper or posterior surface is more or less completely atrophied.

According to M. de Candolle, the calyx-tube, in the case of the rose, is neither a whorl of leaves, nor a concave axis in the ordinary sense in which those terms are used, but is rather to be considered as a ring-like projection from an axis arrested in its ulterior development.

The secondary projections from the original one correspond to an equal number of vascular bundles, and develope into the sepals, petals, stamens, and ovaries. If these organs remained in a rudimentary condition, the tube of the calyx would be reduced to the condition of a sheathing leaf. The rose flower, then, according to M. de Candolle, may be considered as a sheathing leaf, whose fibro-vascular system is complete, and from which all possible primary projections are developed.[464]

If, as M. de Candolle considers, the leaf and the branch differ merely in the fact that the vascular system is complete in the latter, and partly atrophied in the former, it would surely be better to consider the "calyx-tube" of the rose as a concave axis rather than as a leaf, seeing that he admits the fibro-vascular system to be complete in the case of the rose.

With reference to this point the reader is referred to Mr. Bentham's account of the morphology and h.o.m.ologies of the _Myrtaceae_ in the 'Journal of the Linnean Society,' vol. x, p. 105. See also _ante_, pp.

71, 77.

Some doubts also exist as to the nature of the beak or columella of such fruits as those of _Geraniaceae_, _Malvaceae_, _Umbelliferae_, _Euphorbiaceae_, &c. The nature of the organ in question may probably be different in the several orders named; at any rate the subject cannot be discussed in this place, and it is mentioned here because, now and then, it happens that the organ in question is completely wanting, and hence affords an ill.u.s.tration of suppression.

FOOTNOTES:

[464] 'Theorie de la feuille.' p. 24.

CHAPTER II.

SUPPRESSION OF FOLIAR ORGANS.

This subject may be considered, according as the separate leaves of the stem or of the flower are affected, and according as either the number of members of distinct whorls, or that of the whorls themselves, is diminished.

The terms aphylly, meiophylly, and meiotaxy may be employed, according as the individual leaves are altogether wanting, or with reference to the diminished number of parts in a whorl, or a decrease in the verticils.

=Aphylly.=--Entire suppression of the leaves is a rare phenomenon. Under ordinary circ.u.mstances it occurs in most _Cactaceae_, in some of the succulent Euphorbias, and other similar plants, where the epidermal layers of the stem fulfil the functions of leaves. But even in these plants leaf-like organs are present in some stage or another of the plant's life.

Partial suppression of the leaf occurs sometimes in compound leaves, some or other of the leaflets of which are occasionally suppressed.

Sometimes, as Moquin remarks, it is the terminal leaflet which is wanting, when the appearance is that of _Cliffortia_, at other times the lateral leaflets are deficient, as in _Citrus_ or _Phyllarthron_.

_Ononis monophylla_ and _Fragaria monophylla_ may be cited as instances of the suppression of the lateral leaflets. If the blade of the leaf disappears entirely, we have then an a.n.a.logous condition to that of the phyllodineous acacias.

With reference to the strawberry just mentioned, d.u.c.h.esne, 'Hist. Nat.

Frais.,' p. 133, says that this was a seedling raised from the _fraisier des bois_, and the characters of which were reproduced by seed, and have now become fixed. The monophyllous condition has been considered to be the result of fusion of two or more leaflets, but however true this may be in some cases, it is not the case with this strawberry. M. Paillot states that he has found the variety in a wild state.[465]

In like manner varieties of the following plants occur with simple leaves, _Rosa berberifolia_ (_Lowea_), _Rubus Idaeus_, _Robinia pseudacacia_, _Fraxinus excelsior_, _Sambucus nigra_, _Juglans nigra_, &c.

In one instance seen by the writer every portion of the leaf of a rose was deficient, except the stipules and a small portion of the petiole.

(See abortion.)

=Meiophylly.=--A diminished number of leaves in a whorl occasionally takes place; thus, in some of the _Stellatae_, and frequently in _Paris quadrifolia_, the number of leaves in the verticil is reduced. Care must be exercised in such instances that an apparent diminution arising from a fusion of two or more leaves be not confounded with suppression.

=Meiophylly of the calyx or perianth.=--A lessened number of sepals is not a very common occurrence among dicotyledonous plants. Seringe figures a proliferous flower of _Arabis alpina_ with two sepals only, and a similar occurrence has been noticed in _Diplotaxis tenuifolia_.

In _Cattleya violacea_ the writer has met with a flower in which the uppermost sepal was entirely wanting, while two of the lateral petals were fused together. Moquin records that in some of the flowers of _Chenopodiaceae_, in which the inflorescence is dense, a suppression of two or three sepals sometimes occurs. The species mentioned are _Ambrina ambrosioides_, _Chenopodium glauc.u.m_, and _Blitum polymorphum_.

=Meiophylly of the corolla.=--Suppression of one or more petals is of more frequent occurrence than the corresponding deficiency in the case of the sepals. Among _Caryophyllaceae_ imperfection as regards the numerical symmetry of the flower is not uncommon, as in species of _Cerastium_, _Sagina_, _Dianthus_, &c. In _Ranunculaceae_ the petals are likewise not unfrequently partially or wholly suppressed. A familiar ill.u.s.tration of this is afforded by _Ranunculus auricomus_, in which it is the exception to find the corolla perfect.[466] Some varieties of _Corchorus acutangulus_ in west tropical Africa are likewise subject to the same peculiarity. Amongst _Papilionaceae_ absence of the carina or of the alae is not uncommon, as in _Trifolium repens_, _Faba vulgaris_, &c.

Moquin relates a case of the kind in the haricot bean, in which the carina was entirely absent, and another in the pea, where both carina and alae were missing, thus reducing the flower to the condition that is normal in _Amorpha_ and _Afzelia_. Suppression of the upper lip in such flowers as _Calceolaria_ has been termed by Morren "apilary."

In _Orchidaceae_ entire absence of the labellum, frequently without any other perceptible change, is of common occurrence. The writer has seen numerous specimens of the kind in _Ophrys apifera_ and _O. aranifera_; also in _Dendrobium n.o.bile_, _aerides odoratum_, _Cypripedium villosum_, _Listera ovata_, &c. Morren[467] mentions a.n.a.logous deficiencies in _Zygopetalum maxillare_, _Calanthe_ sp., and _Cattleya Forbesii_. In most of these there was also a fusion of the two lower sepals, which were so twisted out of place as to occupy the situation usually held by the labellum. At the same time the column was partially atrophied. To this deficiency of the lip the author just quoted proposed to apply the term acheilary, [Greek: a-cheilarion]. Mr. Moggridge has communicated to the author an account of certain flowers of _Ophrys aranifera_, in which the petals were deficient, sometimes completely, at other times one or two only were present.

=Meiophylly of the androecium.=--Suppression of one or more stamens, independently of like defects in other whorls, is not uncommon, even as a normal occurrence, _e.g._ in _Carlemannia_, where the flower, though regular, has only two stamens, and other similar deficiencies are common in Dilleniads.

Seringe relates the occurrence of suppression of some of the stamens in _Diplotaxis tenuifolia_,[468] St. Hilaire in _Cardamine hirsuta_, others in _C. sylvatica_.

In _Caryophyllaceae_ suppression of one or more stamens has been observed in _Mollugo cerviana_, _Arenaria tetraquetra_, _Cerastium_, &c.[469]

Among violets the writer has observed numerous flowers in which two or three stamens were suppressed. Chatin[470] alludes to a similar reduction in _Tropaeolum_, while in flowers that are usually didynamous absence of two or more of the stamens is not unfrequent, _e.g._ in _Antirrhinum_, _Digitalis_, while in a flower of _Catalpa_ a solitary perfect stamen, and a complete absence of the sterile ones usually present, have been observed. This might have been antic.i.p.ated from the frequent deficiencies in the staminal whorl in these plants under what are considered to be normal conditions. Reduction of the staminal whorl is also not unfrequent in _Trifolium repens_ and _T. hybridum_, and has been seen in _Delphinium_, &c.[471]

=Meiophylly of the gynoecium.=--Numerical inequality in the case of the pistil, as compared with the other whorls of the flower, is of such common occurrence, under ordinary circ.u.mstances, that in some text-books it is looked on as the normal condition, and a flower which is isomerous in the outer whorls is by some writers not considered numerically irregular if the number of the carpels does not coincide with that of the other organs.

But in this place it is only necessary to allude to deviations from the number of carpels that are ordinarily found in the particular species under observation. As ill.u.s.trations the following may be cited:--_Arenaria tetraqueta_, which has normally three styles, and a six-valved capsule, has been seen with two styles, and a four or five-valved capsule. Moquin relates an instance in _Polygala vulgaris_ where there was but a single carpel, a condition a.n.a.logous to that which occurs normally in the allied genus _Mozinna_. _Reseda luteola_ occasionally occurs with two carpels only, while Aconites, Delphiniums, Nigellas, and Paeonies frequently experience a like diminution in their pistil.

In a flower of _Papaver Rhaeas_ the writer has recently met with an ovary with four stigmas and four parietal placentae only, and to Mr.

Worthington Smith he is indebted for sketches of crocus blooms with two, and in one instance only a solitary carpel.

Moquin cites the fruit of a wild bramble (_Rubus_) in which all the little drupes which go to make up the ordinary fruit were absent, except one, which thus resembled a small cherry. In _Crataegus_ the pistil is similarly reduced to a single carpel, as in _C. monogyna_.

The writer has on more than one occasion met with walnuts (_Juglans_) with a single valve and a single suture.[472] If the ovary of _Juglans_ normally consisted of two valvate carpels, the instances just alluded to might possibly be explained by the suppression of one carpel, but the ovary in _Juglans_ is at first one-celled according to M. Casimir de Candolle.

Among monocotyledons _Convallaria majalis_ may be mentioned as very liable to suffer diminution in the number of its carpels, either separately or in a.s.sociation with other changes.[473]