Fig. 122.—Peloric flower of Calceolaria.
Morren[233] describes a form intermediate between the ordinary slipper-shaped corolla and the perfect peloria just described, and which he calls sigmoid peloria. This flower is intermediate in direction between the erect peloria and the ordinary reflected flower. The tube is curved like a swan's neck and is dilated in front into two hollow bosses, such as we see in the lower lip of an ordinary flower; beyond these it is contracted and is prolonged into a slender beak terminating in two hollow teeth, between which is the narrow orifice of the corolla. The colour at the base of the tube inside is as in the perfect peloria; while round the summit of the tube, in both cases, the intensity of colour is greatest on the outside. Now, in a normal flower the deepest colour is within just opposite the orifice of the corolla; this deep colour is also seen outside of the central and most elevated portions of the lower lip. In the peloria the deep colour at the base of the tube represents that which is near the orifice under ordinary circumstances, while the outer patch of colour at the apex corresponds to that formed on the upper surface of the lower lip. On the other hand, in peloric flowers of Cytisus Laburnum, Clitoria Ternatea, Trifolium repens, and other Papilionaceæ, it is the "standard," the form of which is repeated. In the case of peloric aconites[234] the lateral and sometimes the inferior coloured sepals assume the hooded form usually peculiar to the upper sepal only, the number of the petals or nectaries being correspondingly increased. Balsams become peloric by the augmentation in the number of spurs.[235] So when orchids are affected with irregular peloria it is the form of the labellum that is repeated, the accessory lips being sometimes the representatives of stamens, which are usually suppressed in these flowers,[236] but at other times the appearance is due simply to the fact that all three petals assume the form usually confined to the lip, the staminal column being unaffected, except that its direction and relative position with reference to the other parts of the flower is different from ordinary. This was the case in some flowers of Phalænopsis equestris sent to me by Mr. Wentworth Buller. Fig. 123 represents a flower of Aristolochia caudata with two lips, for which I am indebted to Mr. W. H. Baxter.
From these cases it is evident that the flowers in question become regular by the repetition of the irregular parts.
Fig. 123.—Two-lipped flower of Aristolochia caudata.
It is probable that peloria may occur in any habitually irregular flower, and that, if more attention were directed to the subject, illustrations might be obtained from a larger number of natural families than can be done at present. It is, however, necessary to exercise discrimination, and not to attribute to peloria all the cases that at first sight appear to be so referable. Thus, Professor Dickson exhibited at the Botanical Society of Edinburgh, December 13th, 1860, four abnormal flowers of the common Indian cress (Tropæolum majus), each presenting a supernumerary spur. On these he remarked that "in Tropæolum the posterior part of the receptacle between the insertion of the petals and that of the stamens is dilated so as to form the spur which is so characteristic in the genus. The position of the spur in a line with the posterior sepal has led many botanists to consider it as a process of that sepal, but the fact of its being situated within the insertion of the petals is conclusive as to its receptacular origin. In the flowers exhibited the supernumerary spur (as if to show its want of connection with any sepal) was placed exactly between a lateral sepal and one of the anterior sepals, sometimes on the one side of the flower and sometimes on the other. These additional spurs were precisely similar to the normal ones, except that they were a little shorter. This abnormality, although at first sight seeming to indicate a pelorian tendency, is no approximation to regularity, from the fact of the extra spur being differently placed, with regard to the sepals, from the normal one."
Peloria of this kind, when perfect, is very often associated with other alterations. Change of direction is one of the most common of these; the usually drooping flower becomes erect, the stamens and style also are changed in direction, while, not unfrequently, either the one or the other (most often the stamens) are entirely suppressed. With this suppression an increase in the size of the flower very generally coincides. The number of parts is also frequently increased; thus, in Antirrhinum majus the corolla, when subjected to peloria, is very generally six-parted, and has six stamens. Fusion of one or more flowers is also a common accompaniment of peloria, as in Digitalis purpurea, in which plant prolification often adds increased complexity to the flower.
It has been stated by Moquin and others that the uppermost flower of an inflorescence is the most subject to peloria; the uppermost flower of Teucrium campanulatum, for instance, is very generally regular. In Calceolaria it is the central terminal flower which is usually peloriated; on the other hand, in Linaria and Antirrhinum the lower flowers, or those on the secondary branches, are quite as often affected as the primary ones. Cassini considered that the spur of Linaria was developed from the lower petal rather than from the upper ones, because there is more room on the side of the flower farthest from the stem than on the opposite side. With reference to this point, M. Godron remarks that in habitually irregular flowers the apex of the peduncle is oblique, and hence the flowers are bent downwards or spread horizontally, but if the receptacle be quite flat and level then the flower is regular. The oblique position causes some of the organs to press on others, and hence induces abortion and suppression of some parts and increased growth in others that are not subjected to pressure. In a terminal peloriated flower of aconite, described by this naturalist, the flower was removed so far from the nearest bracts that all its parts had the chance of growing regularly. In ordinary cases M. Godron considers that the compression of the lateral bracts is the cause of the irregularity of the andrœcium and of the receptacle.[237]