Popular Science Monthly/Volume 42/January 1893/Some Vegetable Malformations
By Prof. BYRON D. HALSTED.
BY malformations are here understood those structures that are so unusual as to attract attention and so curious as to suggest that they are individual freaks to be explained by some peculiarity of surroundings or not at all. They may occur more frequently with some species of plants than with others, but are usually outside of the reign of the rules of inheritance, and therefore not governed by the ordinary laws of vegetative growth.
It is the purpose here first to treat of some of the more common and striking of these monstrosities, and then, if possible, to indicate how these extravagant forms may serve as keys to unlock some otherwise hidden secrets in vegetable morphology.
It is difficult to make any satisfactory classification of these monstrosities, and therefore instances will be given somewhat in the following order—namely, those of stems, of leaves, of flowers, and finally of fruits. One of the most frequent abnormities of the stem is that where, instead of the nearly cylindrical form, it becomes broad and ribbon-shaped. This type of malformation is confined to the less woody stems, as those of the asparagus. Fig. 1 shows such an instance, where the stem broadened out to nearly four inches in some places, while its thickness is less than half an inch. Numerous small side branches arise from the broad surface of this peculiar shoot, while the end is made up of a large number Fig. 1.—Asparagus Fasciation.of small buds fused together. As they grow, the individual stems lose their identity in the common belt of blended shoots. The photograph is made from a specimen brought last spring to the writer's laboratory, where the upper foot or more is still to be seen preserved in a large museum jar.
The sweet-potato vine perhaps most frequently illustrates this broadening of the stem, but upon a less grand scale than that shown in the asparagus. Only last week a student brought me a plant in which all the several vines were like ribbons, an inch or more in width and several feet in length. It is only a singular instance of a failure of the young formative branches to separate as they are developed from the closely situated buds at the tip; but that this failure should be constant in all the branches of a plant is more difficult to explain.
The reader will call to mind several other kinds of plants that illustrate this same abnormity, to which botanists have given the name of fasciation, from the resemblance of the stem to a bandage. Larkspur and dahlia stems sometimes show the same peculiarity, and, should we here include flower-stalks, the dandelion would afford abundant examples, for the long, hollow scapes are frequently doubled or flattened to a ribbon that sometimes has not strength enough to support the abnormal head of flowers. The garden "cockscomb" (Celosia) owes its attractiveness largely to the unusual development of the stem at its upper end, together with the high color and the fantastic shapes assumed. This is one of the few exceptions to the rule that a fasciation of the stem is not constant.
Last summer, while looking through the nursery rows of a propagator of hardy perennials, my attention was attracted to the stems of the large-flowered bell-flower (Campanula grandiflora), Instead of the cylindrical stem and the loose spray of flowers, these two had developed as shown in the asparagus, and from the broad, flat stalk the flowers were closely arranged. At the enlarged end there were several buds and blossoms more or less blended. In one instance three separate flowers were so closely grown together as to appear as a single monstrous blossom. Passing now to leaves, the reader will perhaps first of all think of the so-called "four-leaved" clover, in which, instead of the ordinary three leaflets, there is an additional one, or possiblyFig. 2—Proliferous Rosestwo or more, the abnormity sometimes running as high as seven leaflets. Some years ago, while in Iowa, the writer found a clover plant with fourteen leaves having four leaflets and seventeen with five leaflets, and these outnumbered the ordinary ones. A "sixleaved" leaf found upon another plant had a lobe growing from one side of one leaflet resembling a mouse's ear. There are clover leaves in which the fourth leaflet is shaped like a funnel. The same shape is rarely seen in geranium leaves, and cabbage and lettuce leaves sometimes show strange outgrowths from the middle of the under side. Twin leaves at the most unexpected places are, to say the least, surprising. One such in my possession is of the lilac, which ordinarily has foliage of a well-defined form.
It is when we come to the flower that the greatest absurdities are to be found. Plants may have their stem fasciated and their leaves with strange lobes and incisions, but in the blossom they sometimes go quite "crazy." Gardeners occasionally send or even bring roses that have taken on such peculiar developments that one can scarcely refrain from a smile when the structure is examined. Fig. 2 shows a sample that came to me accompanied by some most difficult questions. Instead of the blossom terminating the branch, as is usually the case, there is a continuation of the cane beyond the flower, where it forms leaves and new buds. This prolification, as it is termed, is found at rare intervals and in a less conspicuous manner in perhaps
a hundred different genera of plants. The plantains show this prolific manner of producing flowers in a marked degree, as also do the garden pinks.
In the doubling of flowers—that is, the change of stamens or pistils or both into petals—there are many strange combinations produced. All gradations between the perfect stamen with its pollen-bearing tip and the normal petal can be found. In such large flowers as the pæonia the malformations seem like a fruitless struggle between two contending forces, one to keep the flower single and sexual and the other to reduce all parts to a barren neutrality. In the lilies a similar confusion arises in the attempt of the blossoms to hold their essential organs while the surrounding conditions are such as to turn them into the more showy petals. All this multitude of instances, while of exceeding interest to the student of floral structures, is perhaps more monotonous than amusing from the point of view of this paper, which deals more particularly with the unexplainable and eccentric than with strange shapes that are the natural result of an underlying law. Thus the garden petunia "doubles" easily, and in so doing loses its stamens, or some of them, and much of its former beauty. In a study of this process some threeFig. 8.years ago, in which hundreds of specimens were examined, a peculiarity of still greater interest than the simple changing of stamens into petals was brought to light. The unusual size of the petals in some of the doubled flowers led to a dissection of them, when it was found that the contents consisted of stamens partly changed into petals and often highly colored, while in the center of all was a small pistil about one third the normal size. Not infrequently the ovarian stamens had their anthers tipped with a small stigmatic surface, thus indicating the close association of the sexual elements in the floral structures. Fig. 3 shows a normal pistil, the one at Fig. 4 is from a doubled blossom, and Fig. 5 shows the secondary pistil at the center.
Last year, while examining some peppers for a fungous disease, a peculiar formation was met with that comes in the same category with the petunia above mentioned. In making a longitudinal section of the fruit, the seed-bearing column was found crowned by a small pepper which in itself was a fruit in miniature. This freak is shown in Fig. 6.
It is an easy step from flower to fruit, for the latter is a part of and a natural result of the former. The prolification seen in the rose and in many other flowers has its counterpart in fruits of various kinds. Thus, strawberries have been known to bear a branch at the free end, and pears sometimes exhibit the same freak. Fig. 7 shows such a fruit with a branch and a number of leaves extending beyond the blossom end.
Instead of a leaf-bearing shoot, the axis is extended by the production of another fruit, or branching may take place in an irregular way, and a structure as monstrous as that shown in Fig. 8 results.
The apple as well as other fruit is not infrequently twinned by the union of two forming buds, as shown in Fig. 9. In others there is less frequently a second row of seed cavities, thus making a "two-storied" fruit, so to speak, as seen in Fig. 10.
Passing below ground, there are more abnormities to be found than most persons are aware of. The peculiar conditions that attend the subterranean habit favor monstrous growths. Not long ago a cluster of sweet potatoes was brought to me. Some were all red upon the surface, others were all yellow, and some were one half red and the other side yellow. The Irish potato is fertile in its freaks. Seemingly not content with the underground situation, potatoes sometimes appear upon the branches among the leaves. Occasionally a potato when planted whole will develop other new and small potatoes beneath the skin and
out of sight, which only calls to mind how a hollow turnip may have its cavity filled with an after-growth of foliage, only to be discovered when the root is cut in two.
Sometimes the abnormal growths bear a strong resemblance to some other object very far from the one really shown. Thus Fig. 11 shows what might well pass for the human hand, but it is nothing more or less than an ear of corn with the grain removed. Instead of ending in the usual way, it has become branched, thus giving rise to the "lingers," while the lower portion of the cob makes a fair-shaped "wrist." The engraving is made from a photograph recently sent from Missouri.
It would be impossible to mention the instances even of abnormal forms in seeds, or to go further and show how there mayFig. 11.—Hand-cob.be monstrous forms that can only be seen through the compound microscope.
The molds, mildews, rusts, smuts, and various blights that feed upon higher plants have their freaks that are sometimes puzzling to those who study these minute structures.
A large museum might be filled with the eccentricities of the vegetable world. Some of them would only teach the lesson of a lack of equilibrium among the laws which determine definite lines of growth. Others would serve to open the door to some hidden fact of vegetable morphology. Thus, the interchange of stamens and pistils in some abnormal blossom teaches the lesson of the common origin of the two essential organs, while the gradation of either or both to floral envelopes indicates that pistils are only petals of a special form for a special purpose. In short, the malformations as we speak of them are only forms in less than their usual disguise. The leaf is the unit of structure in the flower, and the flower is a metamorphosed branch, which may terminate in a seed-vessel, as the pear, or in rare instances in a leafy branch beyond the fruit, thereby corroborating the belief that the fruit is a part of a stem.
Some one has said that when under the influence of an intoxicant the victim throws off his disguise and lets his inner self appear; so likewise the plant, when it for some reason not easily seen departs from the normal, lets the thoughtful student of plant nature get glimpses of truth not otherwise vouchsafed to him. Teratology is not chaos, neither are malformations meaningless. The unit of origin of parts is no better demonstrated than through some of the "inebriated" conditions as found from time to time in the kingdom of plants.