Vegetable Teratology / An Account of the Principal Deviations from the Usual Construction of Plants

by Maxwell T. Masters

An augmentation in the number of parts may arise from several causes, and may sometimes be more apparent than real. True multiplication exists simply as a result of over-development; the affected organs are repeated sometimes over and over again each in their proper relative position, and without any transmutation of form.

Metamorphy, on the other hand, often gives rise to the impression that parts are increased in number, when it may be that the stamens and pistils, one or both, are not so much increased in number as altered in appearance. The double anemones and ranunculus of gardens, amongst many other analogous illustrations, may be mentioned. In these flowers, owing to the petalody of the stamens and pistils, one or both, an impression of exaggerated number is produced, which is by no means necessarily a true one. Fission or lateral subdivision also gives rise to an apparent increase in number; thus, some so-called double flowers, the elements of which appeared to be increased in numbers, owe the appearance merely to the laciniation or subdivision of their petals.

The French botanists, following Dunal and Moquin, attribute an increase in the number of whorls in the corolla, and other parts of the flower, to a process which they call chorisis, and they consider the augmentation to be due to the splitting of one petal, for instance, into several;—somewhat in the same manner as one may separate successive layers of talc one from the other.

English botanists, on the other hand, have been slow to admit any such process, because, in most instances, no alteration in the law of alternation takes place in these double flowers, and in those few cases where the law is apparently infringed, the deviation is explained by the probable suppression of parts, which were they present would restore the natural arrangement of the flower; and, that this is no imaginary or purely theoretical explanation, is shown by some of the Primulaceæ, wherein a second row of stamens is occasionally present in the adult condition, and renders the floral symmetry perfect.

The double daffodil, where there are from forty to fifty petaloid organs instead of fifteen, and wherein each piece exhibits a more or less perfect coronal lobe at the junction of the claw and the limb, has been cited as an objection to chorisis, though it is difficult to see on what grounds.

In Delphinium, as shown by Braun,[376] the stamens and carpels are members of a continuous spiral series, and in the double balsam an extra corolline whorl is produced, without the suppression of the stamens, in the following manner: the ordinary stamens are replaced by petals, the carpels by stamens, while an additional whorl of carpels is produced at the summit of the axis. In this instance, therefore, the doubling is distinctly referrible to an absolute increase in the number of whorls, and not to chorisis.[377]

On the other hand, it must be admitted that there are many cases which are not to be explained in any other way than that suggested by the French botanists before alluded to. Probably, the main difficulty in the way of accepting the doctrine of chorisis is the unfortunate selection of the word used to designate the process; this naturally suggests a splitting of an organ already perfectly formed into two or more portions, either in the same plane as the original organs, "parallel chorisis;" or at right angles to it "collateral chorisis." Indeed, before so much attention had been paid to the way in which the floral organs are developed, it was thought that an actual splitting and dilamination did really take place; Dunal and Moquin both assert as much. The truth would rather seem to be that, in the so-called parallel chorisis at least, the process is one of hypertrophy and over-development rather than of splitting. The adventitious petal or scale is an excrescence or an outgrowth from the primary organ, and formed subsequently to it.

In the case of "compound stamens" the original stamens are first developed each from its own cellular "mamelon," or growing point; and, after a time, other secondary growing points emerge from the primary one, and in this way the stamens are increased in number, without reference, necessarily, to the so-called law of alternation. Outgrowths from leaves, multiplying the laminar surface, are alluded to under the head of hypertrophy, and it is probable that some of the cases of duplication of the flower, or of the formation of adventitious segments outside the ordinary corolla as alluded to in succeeding paragraphs (see Pleiotaxy of the corolla), are due to a similar process.[378]

The formation of parts in unwonted numbers may be merely a reversion to what is supposed to have been the original form, and in this way there may be a restoration of parts that are usually undeveloped or suppressed. There can be little or no doubt that there are in reality six stamens in Orchidaceæ, of which one only, under ordinary circumstances, is developed. When the numerical symmetry is restored, as it sometimes is, it is obvious that the augmentation that occurs is of a different character from that arising from a repetition or renewed development of organs. When the increased number arises from multiplication proper, or from repetition, the ordinary laws of alternation are not interfered with, but if from chorisis or "dédoublement," it may happen that the normal arrangement is disturbed.