FOOTNOTES:

[220] See a paper of Professor C. Morren's on "Floral Stesomy" in 'Bull. Acad. Belg.,' t. xix, part ii, p. 519.

CHAPTER II.
REGULAR PELORIA.

Fig. 116.—Regular Peloria, Delphinium.

Fig. 117.—Sepal, petal, &c., of regular-flowered Delphinium.

Fig. 118—Regular peloria, Viola.

Fig. 119—Double Violet, flower regular, petals multiplied, stamens and pistils petaloid.

When an habitually irregular flower becomes regular, it does so in one of two ways; either by the non-development of the irregular portions, or by the formation of irregular parts in increased number, so that the symmetry of the flower is rendered perfect, as in the original peloria of Linnæus, and which may be called irregular peloria, while the former case may be called regular peloria. This latter appearance is therefore congenital, and due to an arrest of development.[221] As the true nature of these cases has not been in all cases recognised (even Moquin places them under the head of deformities—they being less entitled to rank in that class than are the usual flowers), it may be well to cite a few instances taken from various families. In Delphinium peregrinum I have met with perfectly regular flowers having five sepals and five oblong stalked petals, and a similar occurrence has been noted in other species of this genus. Baillon,[222] in referring to these flowers, points out the resemblance that they bear to the double varieties of Nigella. In the stellate columbines (Aquilegia) of gardens the tubular petals are replaced by flat ones often in increased numbers. In violets both forms of peloria occur, that in which there is an unusual number of spurs, and that in which there are no spurs (var. anectaria). In the more perfect forms of regular peloria occurring in the last-named genus the following changes may be noticed: 1, an alteration in the direction of the flower so that it remains in an erect position, and is not bent downwards as usual; 2, equality of proportion in the sepals and petals; 3, absence of spurs, as also of hairs on the lateral petals; 4, equal stamens whose anthers are sometimes entirely destitute of the prolonged crest which forms so prominent a feature under ordinary circumstances; 5, erect, not curved styles, and the stigmas not prolonged into a beak, but having a more or less capitate form; ovary with three or five cells, ovules normal.

These are cases where the change in question is most strongly marked, the bi-lateral is completely replaced by the radiating symmetry. The absence of the usual nectary, and of hairs on the side petals, the alterations in the form of the style, etc., all show how much the process of fertilisation must be altered from that which occurs under ordinary circumstances. In some of the double violets now cultivated in gardens, a similar regularity of proportion in the parts of the flower may be seen combined with the substitution of petals for stamens and pistils, and with the development of an increased number of petal-like organs.[223] Between these cases and the ordinary spurred forms as well as those with an increased number of spurs, many intermediate forms may be met with. That such regularity should occur in this family is not to be wondered at seeing that there is a whole subdivision of the order (Alsodeiæ) in which regular flowers are the rule.

In cultivated Pelargoniums the central flower of the umbel or "truss" frequently retains its regularity of proportion, so as closely to approximate to the normal condition in the allied genus Geranium; this resemblance is rendered greater by the fact that, under such circumstances, the patches of darker colour characteristic of the ordinary flower are completely wanting; the flower is as uniform in colour as in shape. Even the nectary which is adherent to the upper surface of the pedicel in the normal flower disappears—sometimes completely, at other tunes partially. The direction of the stamens and style, and even that of the whole flower, becomes altered from the inclined to the vertical position. In addition to these changes, which are those most commonly met with, the number of the parts of the flower is sometimes augmented, and a tendency to pass from the verticillate to the spiral arrangement manifested. Schlechtendal mentions some flowers of Tropæolum majus in which the flowers were perfectly regular and devoid of spurs[224], while in the double varieties, now commonly grown in greenhouses, the condition of parts is precisely the same as in the double violet before alluded to. Among the Papilionaceæ the Laburnum and others have been noticed to produce occasionally a perfectly regular flower in the centre, or at the extremity of the inflorescence, though the peloria in this flower is usually irregular. In the Gentianaceous genus Halenia, H. heterantha is remarkable for the absence of spurs. Amongst Gesneraceæ, Bignoniaceæ, Scrophulariaceæ, and other families of like structure, regular peloria is not uncommon. Fig. 120 represents a case of this kind in Eccremocarpus scaber, conjoined, as is frequently the case, with dialysis or separation of the petals.[225] Many of the cultivated Gloxinias also show erect, regular, five stamened flowers, but these are probably cases of irregular peloria.

Fig. 120.—Regular peloria, Eccremocarpus scaber.

A solitary flower of Pedicularis sylvatica was found by the Marquis of Stafford near Dunrobin Castle in Sutherlandshire, in which the usual ringent form of the corolla was replaced by the form called salver-shaped. There were six stamens, four long and two short. Sir W. Hooker and Mr. Borrer are stated to have found a similar flower in the same locality in 1809.[226]

The passage of ligulate to tubular corollas among Compositæ is not of such common occurrence as is the converse change. I owe to Mr. Berkeley the communication of a capitulum of a species of Bidens, in which there was a transition from the form of ligulate corollas to those that were deeply divided into three, four, or five oblong lobes. These then were instances of regular peloria.

Fig. 121.—Flower of Cattleya marginata. Lip replaced by a flat petal.

In Orchidaceæ a similar change is not by any means infrequent; in a few, indeed, a regular flower is the normal character, as in Dendrobium normale, Oncidium heteranthum, Thelymitra, etc. Fig. 121, reduced from a cut in the 'Gardeners' Chronicle,' 1854, p. 804, represents an instance of this kind in Cattleya marginata.

From the same journal the following account of a case of peloria in Phalænopsis Schilleriana is also cited as a good illustration of this peculiar change. The terminal flower differed entirely from all the others; instead of the peculiar labellum there were three petals all exactly alike, and three sepals also exactly alike; the petals resembled those of the other flowers of the spike, and the upper sepal also; but the two lower sepals had no spots, and were not reflexed as in the ordinary way: thus, these six parts of the flower were all in one plane, and being close together at their edges, made almost a full round flower; the column and pollen-glands were unaffected. Professor Reichenbach also exhibited at the Amsterdam Botanical Congress, of 1865, a flower of Selenipedium caudatum with a flat lip.

M. Gris[227] has placed on record some interesting cases of peloria of this kind in Zingiber zerumbet; in the more complete forms the andrœcium or staminal series was composed of six distinct pieces, the three inner of which were fertile, while in the ordinary flower the andrœcium is composed of two pieces, "a lip" and a fertile stamen. "Is it not a matter of regret," says M. Gris, "to be obliged to call the latter the normal flower?"

Under this head may likewise be mentioned those cases in which the normal, or at least the typical symmetry of the flower is restored by the formation of parts usually suppressed; thus Moquin cites an abnormal flower of Atriplex[228] hortensis described by M. Fenzl as having a true calyx within the two bracts that usually alone encircle the stamens. Adanson, also cited by Moquin, found a specimen of Bocconia with a corolla. Arum maculatum has likewise been met with provided with a genuine perianth as in Acorus and other Orontiads. The unusual development of the sexual organs in diclinous flowers has been alluded to under the head of heterogamy, and other cases where the symmetry of the flower is rendered regular, by the development of parts ordinarily suppressed, will be found in the chapters relating to deviations from the usual number of organs.

This change, or rather this persistence of a form that is usually transient, is generally accompanied by some other alterations. Change of direction, as has been already mentioned, is one of the most common of these; separation of the petals (Antirrhinum, Verbascum, &c.), and even their appearance in leaf-like guise, are not infrequent (Delphinium, Antirrhinum, Verbascum, &c.) At other times multiplication or increased number of the whorls of petals takes place, often, but not always, at the expense of the sexual organs of the flower. Perhaps even more frequent is the increased number of parts in the same whorl in cases of regular peloria; thus, in the Pelargoniums before alluded to, the parts of the flower are frequently regulated by the number six instead of five.

This form of peloria is most generally met with in flowers that are placed at the end or in the centre of the inflorescence, or in such flowers as occur singly at the end of the flower-stalk, as in Tropæolum, Viola, &c. It would hence seem as if the freedom from pressure or restriction on one side allowed the flower to develop equally in all directions, and thus to produce regularity of form.

It is obvious, from what has been before said, that the process of fertilisation is in many cases interfered with and altered by the change in the conformation or the flower.

From overlooking the occasional existence of this form of peloria, new genera have sometimes been formed on insufficient grounds. The genus Aceranthus, for instance, consists of species of Epimedium in which the customary spurs are not formed.[229]

The occurrence both of regular and irregular peloria on the same plant has frequently been observed in Linaria. It has also been remarked that the seedlings raised from these forms are not always constant; thus, the late Mr. Crocker, formerly foreman in the Royal Gardens, Kew, informed me that he fertilised some flowers of a drooping Gloxinia with their own pollen, and that when the seedlings blossomed a large number of them produced the erect regular flowers.

From what has been already said it will be seen that regular peloria is closely allied to what Morren called epanody, or a return to the normal condition. The reversion of a monstrous form to the normal one, as, for instance, when the fern-leaved beech reverts to the normal type, was called by the same author epistrophy.[230]

The following are the genera in which regular peloria has been most often observed. It must, however, be remarked that in some of the flowers recorded as peloric there is no indication as to which form of peloria the case should be referred to. For other illustrations refer to chapters on Heterogamy, Number, Irregular Peloria, &c.

In addition to the references already given, further information on this subject may be gained from consulting the following publications. See also Irregular Peloria.

Giraud, 'Bot. Soc. Edinb.,' Dec. 12, 1839, Antirrhinum. Dareste, 'Ann. Sc. Nat.,' ser. 2, 1842, xviii, p. 220, Delphinium. C. Morren, 'Fuchsia,' p. 90, Calceolaria, 'Bull. Acad. Belg.,' xx, part ii, p. 57; and E. Morren, 'Bull. Acad. Belg.,' 2nd ser., xix. p. 224, Gloxinia. Richard, 'Mém. Soc. d'hist. nat.,' ii, p. 212, tab. 3. Lindley, 'Journ. Linn. Soc.,' iii, p. 9, Dendrobium. Michalet, 'Bull. Soc, Bot. France,' vii, p. 625, Betonica. Gubler, 'Bull. Soc. Bot. Fr.,' ix, 81, 'Des anomalies aberrantes et regularisantes.' Reichenbach fil. 'De pollinis orchid. genesi ac structura,' 1852, Oncidium. Clos, 'Mém. Acad. Toulouse,' vi, 1862, Salvia. Caspary, 'Verhandl. Phys. Œkon. Gesell. Königsberg,' 1860, i, 59, Columnea. Bureau, 'Bull. Soc. Bot. Fr.,' 1861, vol. viii, p. 710, Streptocarpus. Darwin, 'Variation of Animals and Plants,' ii, pp. 59 and 396. Godron, 'Ex. Bull. Bot. Soc. Fr.,' xiv, p. 165, 'Rev. Bibl.,' Wistaria. Marchand, 'Adansonia,' iv, p. 172, Lonicera. Baillon, 'Adansonia,' v, p. 177, 'Sur la regularité transitoire de quelques fleurs irreg.,' shows that during the development of some flowers which begin and end by being irregular, there is an intermediate state when all the parts are regular. Helye, 'Revue Horticole,' Sept., 1868, p. 327. In this last paper, published as this sheet is going through the press, the author states that he has raised from seed three generations of plants of Antirrhinum with regular spur-less flowers. The original wild plant was only partially peloric, but all the flowers produced on its descendants were regular.