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

by Maxwell T. Masters

Co-relation.—The importance of this subject first prominently brought into notice by Geoffroy St. Hilaire gains in force daily. Rarely is a malformation an isolated phenomenon, almost always it is associated, from the operations of cause or effect, with some others. Instances of this co-relation have been cited in the preceding pages, and many more might have been mentioned, had the consideration of the relationship between form and function formed part of the plan of this volume. A change in itself slight, often acquires importance from its association with other alterations. This is particularly well seen in the case of the receptacle. Let an ordinarily concave thalamus remain, from defective development, flat, and how great the change in the appearance of the flower. Let the usually contracted receptacle be lengthened, and the whole aspect of the flowers so affected is altered to such an extent that, were their history not known, botanists would have no hesitation in assigning them to widely separate groups in their schemes of classification. Peloria, too, of either form, affords excellent illustrations of the co-existence of one changed condition with another. Not only is the form of one set of organs altered, but the number, the relative proportion, and the direction of the other organs of the flower are altered likewise.[562] Not only is the whole symmetry changed, but the physiological operations carried on in the flower undergo corresponding alterations.

There are certain co-relations which do not appear to have hitherto attracted the attention they merit; such, for instance, is that which exists between the particular period at which an organ is developed and its position and form. In normal morphology this has, to some extent, been worked out, as in the case of definite and indefinite, centrifugal and centripetal inflorescences, and in the definite or indefinite formation of shoots, &c.

Other instances may be cited in the frequent co-existence of regular flowers and definite inflorescence, the terminal position of many peloriated flowers, the relationship between indefinite inflorescence and prolongation of the axis, &c.

Again, the simultaneous evolution of the parts of the flower and their consequent verticillate arrangement, are often associated with the production of different forms from those characteristic of organs developed in succession, and, in consequence, arranged spirally. In the case of simultaneous development we meet with a repetition of whorls, as in what are termed hose-in-hose flowers (flores duplicati, triplicati, &c.), and also with cases of peloria. In instances where the organs are formed successively in spiral order, we meet with such changes as median prolification, petalody, and phyllody. All these are alterations which we might anticipate from the activity of the growing point being checked at a certain stage in the one case, while it is continuous in the other. This relationship between the definite and indefinite modes of growth and the form of the several organs of the flower, is more constant in reality than it may appear to be from a perusal of the lists of genera in the foregoing pages, in which it was not possible to show sufficiently well the comparative frequency of any given changes in individual plants. Had it been possible to give statistics setting forth the frequency of certain deviations in plants or groups having a particular organisation, as compared with the rarity of their occurrence in other plants of a different conformation, these co-relationships would have been rendered much more evident. A hundred different plants, for instance, may be named in any particular list, of which fifty shall be of one type of structure, and the remainder of another. And the co-relative changes in each fifty may appear to be evenly balanced, but so far is this from being the case, that the frequency of the occurrence of a particular change, in one species in the list, may be so great as far to exceed the instances of its manifestation in all the rest put together. This difficulty is only very partially obviated by the addition of the * to signify especial frequency of occurrence of any given malformation in the plants to whose names it is affixed.

Compensation.—But little further need be said on this head. An atrophied condition of one part is generally associated with an hypertrophied condition of another, and scarcely a change takes place in one direction, but it is associated with an inverse alteration in some other. This principle is not universal, and its application must not be unduly strained. It requires specially to be considered in reference to differences in the degree or kind of functional activity exercised by the organs implicated—points beyond the scope of the present volume.

Teratology and classification.—Lastly, there remain to be mentioned the bearings of teratology on systematic botany. There are those who would entirely exclude teratology from such matters. It may be expedient to do so when the object sought is one of convenience and facility of determination only, but when broader considerations are concerned, teratology must no more be banished than variation. In most instances the one differs but in degree from the other. If variation affords aid in our speculations as to the affinities and genealogical descent of species and other groups, so does teratology, and in a far higher degree.

Take the characters of exogens as distinct from endogens; even under ordinary circumstances, no absolute distinction can be drawn between them. There are plants normally of an intermediate character, while, to take exceptional instances, there are exogens with the leaves and flowers of endogens, and endogens whose outward organisation, at any rate, assimilates them to exogens. Diclinous or monochlamydeous plants owe their imperfect conformation to suppression, and may become structurally complete by a species of peloria. Structurally hermaphrodite flowers become unisexual by suppression, or are rendered incomplete by the non-development of one or more of their floral whorls. Hypogynous flowers become perigynous by adhesion, or by lack of separation; perigynous ones become hypogynous by an early detachment from the receptacle that bears them, or by the arrested development of an ordinarily cup-like receptacle.

How the relative position of the carpels and the calyx may be altered has already been alluded to, as has also the circumstance that while it is common to find an habitually inferior or adherent ovary becoming superior or free, it is much more rare to find the superior ovary adherent to the receptacle or to the calyx.[563] Regular and irregular peloria, too, serve to show how slight are the boundaries, not only between different genera, but also between different families.