FOOTNOTES:

[464] 'Théorie 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 circumstances it occurs in most Cactaceæ, 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 analogous condition to that of the phyllodineous acacias.

With reference to the strawberry just mentioned, Duchesne, '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 Idæus, 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 Stellatæ, 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 Chenopodiaceæ, in which the inflorescence is dense, a suppression of two or three sepals sometimes occurs. The species mentioned are Ambrina ambrosioides, Chenopodium glaucum, 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 Caryophyllaceæ imperfection as regards the numerical symmetry of the flower is not uncommon, as in species of Cerastium, Sagina, Dianthus, &c. In Ranunculaceæ the petals are likewise not unfrequently partially or wholly suppressed. A familiar illustration 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 Papilionaceæ absence of the carina or of the alæ 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 alæ 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 Orchidaceæ 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 nobile, Ærides odoratum, Cypripedium villosum, Listera ovata, &c. Morren[467] mentions analogous 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, α-χειλαριον. 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 andrœcium.—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 Caryophyllaceæ 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 Tropæolum, 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 anticipated 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 gynœcium.—Numerical inequality in the case of the pistil, as compared with the other whorls of the flower, is of such common occurrence, under ordinary circumstances, 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 illustrations 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 analogous to that which occurs normally in the allied genus Mozinna. Reseda luteola occasionally occurs with two carpels only, while Aconites, Delphiniums, Nigellas, and Pæonies frequently experience a like diminution in their pistil.

In a flower of Papaver Rhæas the writer has recently met with an ovary with four stigmas and four parietal placentæ 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 Cratægus 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 association with other changes.[473]

Meiophylly of the flower as a whole.—In the preceding sections a reduction in the parts of each individual whorl has been considered without reference to similar diminution in neighbouring verticils. It more commonly happens, nevertheless, that a defect in one series is attended by a corresponding imperfection in adjoining ones. Thus trimerous fuchsias and tetramerous jasmines may frequently be met with, and Turpin describes a tetramerous flower of Cobæa scandens. Perhaps monocotyledonous plants are more subject to this numerical reduction of the parts of several verticils than are other flowering plants. Thus, in both Lilium lancifolium and L. auratum the writer has frequently met with pentamerous flowers. In Convallaria maialis a like deviation not unfrequently occurs.[474] M. Delavaud has recorded a similar occurrence in a tulip.[475]

Dimerous crocuses may also sometimes be met with. In one flower of this nature the segments of the perianth were arranged in decussating pairs, and the four stamens were united by their filaments so as to form two pairs.

M. Fournier mentions something of the same kind in the flower of an Iris.[476]

Orchids seem peculiarly liable to the decrease in the number of their floral organs. Prillieux[477] mentions a flower of Cattleya amethystina wherein each whorl of the perianth consisted of two opposite segments.

The same observer has put on record instances of a similar kind in Epidendrum Stamfordianum. In one flower of the last-named species the perianth consisted of one sepal only, and one lip-like petal placed opposite to it.[478] Morren[479] describes a flower of Cypripedium insigne, in which there were two sepals and two petals. Of a similar character was the flower found by Mr. J. A. Paine, and described in the following terms by Professor Asa Gray in the 'American Journal of Science,' July, 1866:—"The plant" (Cypripedium candidum) "bears two flowers: the axillary one is normal; the terminal one exhibits the following peculiarities. The lower part of the bract forms a sheath which encloses the ovary. The labellum is wanting; and there are two sterile stamens, the supernumerary one being opposite the other, i.e. on the side of the style where the labellum belongs. Accordingly the first impression would be that the labellum is here transformed into a sterile stamen. The latter, however, agrees with the normal sterile stamen in its insertion as well as in shape, being equally adnate to the base of the style. Moreover, the anteposed sepal is exactly like the other, has a good midrib and an entire point. As the two sterile stamens are anteposed to the two sepals, so are the two fertile stamens to the two petals, and the latter are adnate to the style a little higher than the former. The style is longer than usual, is straight and erect; the broad, disciform stigma therefore faces upwards; it is oval and symmetrical, and a light groove across its middle shows it to be dimerous. The placentæ, accordingly, are only two. The groove on the stigma and the placentæ are in line with the fertile stamens.

Here, therefore, is a symmetrical and complete, regular, but dimerous orchideous flower, the first verticil of stamens not antheriferous, the second antheriferous, the carpels alternate with these; and here we have clear (and perhaps the first direct) demonstration that the orchideous type of flower has two stamineal verticils, as Brown always insisted."

Fig. 198.—Regular dimerous flower of Calanthe vestita.

Fig. 199.—Regular dimerous flower of Odontoglossum Alexandræ.

Dr. Moore, of Glasnevin, kindly forwarded to the writer a flower of Calanthe vestita (fig. 198), in which there were two sepals only, anterior and posterior, and two petals at right angles to the two sepals. The lip was entirely wanting, but the column and ovary were in their usual condition. In Odontoglossum Alexandræ a similar reduction of parts has been observed by the author (fig. 199).

It is curious to observe in these flowers how precisely one sepal occupies the position of the labellum, and how the lateral petals are displaced from the position they usually occupy, so as to form a regular flower, the segments of which decussate, thus giving rise to a species of regular peloria.

The genus Mælenia was established on a malformed flower of Orchis of similar character to those above mentioned.

Meiotaxy of the calyx.—As already mentioned, this term is here employed to denote those illustrations in which entire whorls are suppressed. Complete deficiency of the calyx in a dichlamydeous flower seems seldom or ever to occur; the nearest approach to it would be in those cases where the calyx is, as it is termed, "obsolete," but here it is chiefly the limb of the calyx which is atrophied, the lower portion being more or less adherent to the ovary. In what are termed monochlamydeous flowers both calyx and corolla are wanting, as in Salicineæ and many other orders.

Meiotaxy of the corolla.—Deficiency of the entire corolla occurs in conjunction with similar reductions in other organs, or as an isolated phenomenon in the many apetalous varieties of plants recorded in books. Deficiency of the corolla was observed in Campanula perfoliata and Ruellia clandestina by Linné, who calls such blooms flores mutilati.[480] Drs. Hooker and Thomson relate a similar occurrence in Campanula canescens and C. colorata. Some plants seem as a normal occurrence to produce flowers of different construction, and are hence termed dimorphic, as in many Malpighiaceæ, Violaceæ, Oxalidaceæ, in some of the flowers of which the petals are altogether wanting, while in others the corolla is developed as usual. This deficiency of the corolla is frequently, but not invariably, associated with an increased fertility. Thus, in some violets the flowers produced in summer, and in which the petals are either entirely suppressed or are more or less atrophied, are always fertile, while the blossoms developed in spring, and in which the petals are always present, are much less fertile. In Oxalis Acetosella there are two forms of flower, the one with, the other without, petals, but both seem equally fertile. Linné remarks that many plants which, in warm latitudes, produce a corolla, do not do so when grown in colder climates. Thus, certain species of Helianthemum are apetalous in Lapland. In the Pyrenees, according to Bentham, the flowers of Ajuga iva are constantly deprived of their corolla.[481]

Apetalous flowers have been noted most frequently in the following plants:

The following references apply some to apetalous and others to dimorphic flowers, but it must be remembered that the latter plants are not necessarily wanting in petals or stamens, &c., though the functional activity of the parts may be impaired:

A. de Jussien, 'Monogr. Malpigh.,' pp. 82, 334. Torrey, 'Fl. New York,' i, p. 428. Hooker and Thomson, 'Journ. Linn. Soc.,' ii, p. 7, Guillemin, 'Archiv. de Botan.,' i, p. 412. Michalet, 'Bull. Soc. Bot. Fr.,' vii. p. 465. Müller, 'Bot. Zeit.,' 1857, p. 729. 'Natural History Review,' July, 1862, p. 235.

Meiotaxy of the andrœcium.—Complete suppression of the stamens occurs normally in the female flowers of unisexual plants, and, as an accidental occurrence, is not very uncommon. Erica Tetralix is one of the plants in which this is said to happen. The variety anandra is said to have been known in France since 1635. Cornuti speaks of it in his 'Enchiridion.' In 1860 M. du Parquet discovered it in peaty woods near Nangis (Seine et Marne).

Many Umbelliferæ, such as Trinia vulgaris, present a like deficiency, while it is of common occurrence among Rosaceæ and Pomaceæ. In the latter group the St. Valery apple, so often referred to, is an illustration. To obtain fruits from this variety it is necessary to apply pollen from another flower, a proceeding made the occasion of festivity and rejoicing by the villagers in some parts of France. In some of the Artemisias, especially in Artemisia Tournefortiana, all the florets have been noticed to be female, owing to the suppression of the stamens, and this suppression is associated with a change in the form of florets.[482] Mr. Moggridge has communicated to the author flowers of Thymus Serpyllum from a plant in which all the stamens were deficient, the flower being otherwise normal.

M. Dupont has given a list of nineteen species of Chenopodiaceæ in which female flowers are occasionally produced, owing to the entire suppression of the staminal whorl.[483]

Flowers the subjects either of regular or irregular peloria, q. v., are often destitute of some or all their stamens, e.g. Calceolaria, Linaria, Viola, &c., while in cases of synanthy suppression of some of the parts of the flower, and specially of the stamens, is of very common occurrence.

Suppression of the andrœcium as a teratological occurrence has been most frequently noticed in the following plants, omitting members of those families whose floral construction is normally incomplete in the majority of instances, and exclusive also of cases of substitution. See also under Heterogamy.

Meiotaxy of the gynœcium.—Complete suppression of the pistil is of more frequent occurrence than that of the stamens, hence more flowers become accidentally unisexual by suppression of the pistil than by deficiency of the stamens.

In many Umbelliferæ, e.g. Torilis Anthriscus, Cicuta virosa, the central flowers are often male, owing to the suppression of the pistil. In many double flowers, owing to the excessive multiplication of petaloid stamens, the pistil is suppressed, in which cases it often happens that the flower is depressed in the centre, as in some garden varieties of Ranunculus. Schlechtendal, in describing a flower of Colchicum autumnale, in which the perianth was virescent, says that, although the stamens were present, the pistil was absent.

In proliferous flowers the pistil is often completely defective, its place being occupied by the adventitious bud or axis.

As in other cases of like nature, suppression of the pistil is very frequently consequent on fusion of flowers or other changes. Thus Morren relates an instance of synanthy in the flowers of Torenia scabra, accompanied by resorption or disappearance of some parts and spiral torsion of others. The pistil was entirely absent in this instance.[484]

M. Gaetano Licopoli places on record an instance where the petals and carpels of Melianthus major were suppressed.[485]

On the whole, the pistil seems less subject to changes of this character than the andrœcium.

Suppression of the pistil has been most frequently recorded in flowers (normally bisexual) of—

Suppression of ovules,—abortion of seeds.—The two cases are taken together, as the effects are similar, though it must be remembered that in the one case the ovules at any rate have been formed, but their development has been arrested, while in the other they have never existed. The precise cause that has determined the absence of seed cannot in all cases be ascertained in the adult condition, hence it is convenient to treat the two phenomena under one head.

Many plants in other than their native climates either produce no fruit at all, or the fruits that are produced are destitute of seed, e.g. Musa, Artocarpus, &c. Some of the cultivated varieties of the grape and of the berberry produce no seeds.

Suppression or abortion of the seed is frequently associated with the excessive development either in size or number of other portions of the plant, or with an altered condition, as when carpels become foliaceous and their margins detached. Hybridisation and cross fertilisation are also well-known agents in diminishing the number and size of seeds.

Meiotaxy of the parts of the flower in general.—In the preceding sections suppression has been considered as it affected individual members of a whorl or separate whorls. It rarely happens, however, that the suppression is limited in this way. More generally several of the parts of the flower are simultaneously affected in the same manner.

A few illustrations are all that is necessary to give as to this point.

One of the most familiar instances is that of the cauliflower or broccoli, where the common flower-stalk is inordinately thickened and fleshy, while the corolla and inner parts of the flower are usually entirely suppressed; the four sepals can, however, generally be detected.

Maximowicz describes a Stellaria (Kraschenikovia) in which the upper flowers are male only, while the lower ones, which ultimately become buried in the soil, have neither petals, stamens, nor styles, but the walls of the capsule are fleshy, and enclose numerous seeds.[486]

Kirschleger[487] mentions a variety of Lonicera Caprifolium, which was not only destitute of petals but of stamens also.

In some species of Muscari and Bellevalia the uppermost flowers of the raceme show more or less complete suppression of almost all the part of which the flower normally consists. In those cases where an imperfect perianth exists, but in which the stamens and pistils are entirely suppressed, Morren applies the term Cenanthy, κενος, empty.

Complete suppression of the flower.—It is not necessary in this place to allude to that deficient production of flowers characteristic of what is termed by gardeners a "sky bloomer." In such plants often the requisite conditions are not complied with, and the skill of the gardener is shown in his attempt to discover and allow the plant to avail itself of the necessary requirements. We need here only allude to those instances in which provision is made for the production of flowers, and yet they are not produced. A good illustration of this is afforded by the feather-hyacinth, Hyacinthus comosus, in which the flowers are almost entirely suppressed, while the pedicels are inordinately increased in number, and their colour heightened. Something similar occurs in several allied species, and in Bowiea volubilis. The wig plant (Rhus Cotinus) affords another illustration of the same thing. Some tendrils also owe their appearance to the absence of flowers, being modified peduncles; proofs of this may frequently be met with in the case of the vine.

In Lamium album I have seen one of the verticillasters on one side of the stem completely wanting, the adjacent leaf being, however, as fully formed as usual.

General remarks on suppression.—On comparing together the various whorls of the flower in reference to suppression, and, it may be added, to atrophy, we find that these phenomena occur most rarely in the calyx, more frequently in the corolla, and very often in the sexual organs and seeds; hence it would seem as if the uppermost and most central organs, those most subject to pressure and latest in date of development—formed, that is, when the formative energies of the plant are most liable to be exhausted—are the most prone to be suppressed or arrested in their development. When the plants in which these occurrences happen most frequently are compared together, it may be seen that partial or entire suppression of the floral envelopes, calyx, and corolla, is far more commonly met with in the polypetalous and hypogynous groups than in the gamopetalous or epigynous series.

The orders in which suppression (speaking generally) occurs most often as a teratological occurrence are the following:—Ranunculaceæ, Cruciferæ, Caryophyllaceæ, Violaceæ, Leguminosæ, Onagraceæ, Jasminaceæ, Orchidaceæ. It will be observed that these are all orders wherein suppression of the whole or part of the outer floral whorls takes place in certain genera as a constant occurrence.

Again, it may be remarked that many of these orders show a tendency towards a regular diminution of the assumed normal number of their parts; thus, among Onagraceæ, Circeia and Lopezia may be referred to, the former normally dimerous, the latter having only one perfect petal. So in fuchsias, a very common deviation consists in a trimerous and rarely a dimerous symmetry of the flower.

Although, if the absolute number of genera or orders be counted, there appears to be little difference in the frequency of the occurrence of suppression in irregular flowers as contrasted with regular flowers, yet if the individual instances could be counted in the two groups respectively it would be found that suppression is more common among irregular than in regular flowers. Thus, the number of individual instances of flowers in which the perianth is defective is comparatively large among Violaceæ, Leguminosæ, and Orchidaceæ. This statement hardly admits of precise statistical proof; still, it is believed that any observer who pays attention to the subject must come to the same conclusion. This is but another illustration of the fact that conditions which are abnormal in one plant constitute the natural arrangement in others.

As to the suppressions that occur in the case of the sexual organs, and the relations they bear to dimorphism, diclinism, &c., but little stress has been laid on them in this place, because their chief interest is in a physiological point of view, and is treated of in the writings of Mohl, Sprengel, Darwin, Hildebrand, and others. All that need be said here is, that teratology affords very numerous illustrations of those intermediate conditions which are also found, under natural circumstances, between the absolutely unisexual flowers, male or female, and the structurally hermaphrodite ones. Rudimentary stamens or pistils are of very common occurrence in monstrous flowers. See Chapter on Heterogamy, &c.