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

by Maxwell T. Masters

All the parts of the flower may be thus affected; but, as might have been anticipated from the foliaceous nature of the sepals, the new bud usually arises from within the axil of one of those organs. Next in frequency to the calyx, the pistil is subjected to this change—the carpels in such a case being disunited and leaf-like. The petals rank next, and lastly the stamens; these latter, indeed, are usually, but not invariably, absent, the new growth occupying their position. Hence it may well be that when such is the case, there is no real axillary prolification, but rather the substitution of a bud for a stamen. Generally, however, the position of the accessory bud is such that it may properly be referred to the axil of an undeveloped or rudimentary stamen.

The largest number of instances of this malformation, not merely generically, but also individually, occurs in plants the members of whose floral whorls are not united one to the other; thus, it is far more common in polypetalous plants than in gamopetalous ones. In the prolified flowers belonging to the latter group, the sepals, if not actually uncombined, are only united for a short distance. The same relationship, but in a much less degree, exists in the case of median prolification, as that aberration is likewise most commonly met with in polypetalous flowers. Another feature of interest is the rarity with which axillary prolification is found in irregular gamopetalous blooms. It may be that the irregular and comparatively excessive growth in some parts of these flowers, as compared with others, may operate in checking any luxuriant tendency in other directions.

As in the case of median prolification, plants having an indefinite inflorescence are more liable to be affected with ecblastesis than those having a definite one. The degree of branching of the inflorescence may be noticed, as this deformity is far more common in plants whose peduncles are branched than in those which have either a solitary flower or an unbranched flower-stalk. More than two thirds of the entire number of genera cited as the subjects of this malformation have a branched inflorescence of some form or other; and about two thirds of the cases occur in genera having some form of indefinite inflorescence. If individual instances could be accurately computed, the proportion would be even higher.

Fully three fourths of the entire number of genera recorded as occasionally the subjects of this irregularity possess in their usual state some peculiarity of the thalamus; for instance, in about a third of the whole number of genera the thalamus is more or less prolonged between some or other of the floral whorl, e.g. Caryophyllaceæ, Potentilla, Anemone, Dictamnus, Umbelliferæ, &c. About one fourth of the genera have numerous stamens or numerous carpels, or both, springing naturally from the thalamus. In others (about one sixth) the thalamus is enlarged into a disc, or else presents one or more glandular swellings, e.g. Reseda, Nymphæa, Cruciferæ. In the last-named family, as has been already remarked, prolification is very common. It would be interesting to ascertain precisely what part of an inflorescence is most liable to this affection; but as information on this point is but rarely given in the records of these cases, I can only give the results of my own observations, which go to show that, in a many-flowered inflorescence, those flowers at the outside, or at the lower portion, seem to be more frequently the subjects of this change than those situated elsewhere. This may probably be accounted for by the fact that the malformation is met with most generally in plants with an indefinite form of inflorescence, and therefore the lowermost or outermost flowers are most fully nourished; the upper flowers being in a less advanced condition, the change is more likely to be overlooked in them; or it may be that from the unusual luxuriance in the lower flowers, the upper ones may be either present in their ordinary condition, or may be (as indeed frequently happens) stunted in the size and proportion of their several parts.

Axillary foliar prolification of the flower.—The formation of an adventitious leaf-bud in the axil of any of the parts of the flower is not of such common occurrence as the development of a flower-bud in similar situations, nor is it so frequent as median foliar prolification. I have seen leafy shoots proceeding from the axils of the sepals in the flowers of Brassica, and a similar occurrence has been noticed in Caltha palustris, Herreria parviflora, and other plants. Dr. Marchand's flowers of Anagallis, previously referred to at p. 117, showed good illustrations of this occurrence, as also some specimens described by Kirschleger in A. phœnicea.[134] Steinheil has figured and described[135] a flower of Scabiosa in which there was an adventitious formation of leafy shoots in the axil of the outer calyx. In some flowers, such as Convolvulus, Anemone, &c., the exact nature of the sub-floral leaves is uncertain, i.e. it is open to doubt whether the organs in question are bracts or leaves pertaining to the inflorescence, or whether they are really parts of the flower. When leafy shoots are formed in the axils of such organs, the adventitious growth may be referred to extra-floral prolification, prolification of the inflorescence that is, or to axillary prolification, according to the view taken of the real nature of the sub-floral leaves. So far as the mere occurrence of prolification is concerned, it is not very material which view be adopted. The same remark applies to cases where leaf-buds occur on the outer surface of inferior ovaries, as in Rosaceæ, Pomaceæ, Philadelphus, or Tetragonia expansa, as elsewhere mentioned.

It would seem more consistent with the general arrangements of parts, that the adventitious buds should be formed more frequently outside than within the flower proper.

Knight[136] figures and describes the occurrence of small tubers or fleshy leaf-buds in the axils of the sepals of a potato, a curious illustration of the real morphological nature of the tuber.

Axillary floral prolification of the flower.—As already stated, this is of more common occurrence than the formation of a leaf-bud in a similar situation. Any of the parts of the flower may thus subtend a flower-bud, though probably the new buds more frequently originate in the axils of the sepals than in the other whorls. In Cruciferæ the change in question is, relatively speaking, very common. In cauliflowers and broccoli I have frequently met with stalked flowers proceeding from the axils of the sepals, so also in some fuchsias I have seen a ring of stalked flower-buds alternating with the petals, which, together with the stamens and pistil, remained unaffected. The number of parts in the supernumerary structures is generally less than the normal flowers.

In Mr. Herbert Spencer's 'Principles of Biology,' part iv, p. 37, are figured and described some monstrous inflorescences in Angelica and other Umbelliferæ, from which, amongst other things, the author draws the conclusion that there is no absolute distinction between leaf and branch. Without staying for the moment to discuss this matter, it may here be said that the Umbellifers in question apparently owe their peculiarities rather to axillary prolification within the flower, or to prolification of the inflorescence, than to an actual transformation of a flower or any portion of a flower into an umbellule.[137]

In the 'Gardeners' Chronicle,' 1855, p. 551, an instance is figured of the production of a supernumerary flower proceeding from the axil of a stamen in a species of Nymphæa (fig. 65). The ovary in this case was wanting, but in its place was a tuft of small leaves. It is curious that among Dr. Kirk's drawings of east tropical African plants now at Kew, there should be one representing a precisely similar state of things. The species in both instances was Nymphæa Lotus, or a cultivated variety of it.