THE ROMANCE OF THE FERN.

Hawera & Normanby Star, Volume XLII, Issue XLII, 6 January 1923, Page 2

THE ROMANCE OF THE FERN.

a AN INTERESTING STORY.

(By Fawcett Clapper ton, B.Sc.) Ferns do not often figure at tbe shows. They are the Cmderellas of the garden, valued only because they are supposed to be indifferent to sunshine and useful for covering up places where nothing else will grow. But the beauty and suggestiyeness of a welldesigned fernery, out of doors or in, will convince ■anyone that the esoteric cult of the fern need_ not be only for botanists, though, it .is true, the , scientific Study of ferns is oi very particular value. Charming effects are obtainable by the use of rockwork; and old stumps of trees may be employed Ito support the climbing Lygodium or ! the epiphytic Platycerium, as well as | all sorts of mosses, selaginellas, and i liverworts. A great variety of species ■ can be grown under one roof; the j different natural conditions, as regards j light and moisture, being approximated by a careful discrimination in the f positions allotted to the species. .'lf j'the'fernery is to suggest the "gloom ! divine" of the; forest,. or epitomise the flower less world of a bygone age, only ferns and their,/ allies should be admitted,, It is unnecessary—though as a concession permissible—to have a few of those woodland flowers whose habitat is that of the typical fern. Ferns are worthy of cultivation for their own sakes, and not because their elegant foliage enhances the colours of flowers. They will be found to satisfy the aesthetic sense as well as stimulate interest in their peculiar life history. I Th© discovery that ferns are flowerless sets up an inquiry as to how they procreate their kind. Even in" ancient times their lack of flowers seems to haye stimulated superstitious wonder. Hilderic Friend, in "Flowers and Flower Lore,'' tells us that in many parts of Europe < there is a tradition that on the eve of St. John the fern puts forth, a small and evanescent blue ' flower at the dim hour of twilight, that thereafter seed sets and ripens, I and falls.at midnight. Science puts ml place of this story pne not leg? stringe". ] _ The seed of an Ordinary flowering plant j is formed after the union of the con-j tents of qi grain of pollen with the egg-cell contained in an ovule of the same or another flower., This union is brought about by various agencies; the pollen from one-"flower being conveyed to the stigma of another by insects, wind, or water, or placed on the stigma of the same flower by the move--ment of the' stamens in which the pollen is formed. A < seed contains a sexually farmed embryo, supplied with the food /necessary to carry it over the critical period between germination and a state of full self-support. t The;'fern produces no such-seed. In-'' • stead, we find the reproductive bodies in the form of a fine dust called spores. These grow in neat spore-cases, usually on the back of the frond, and the structure of the spore-case is one of the chief characters by which the Systematise distinguishes lone species from another. Every gardener knows that when spores are germinated on damp soil they give rise, not to ferns, but to tiny plantlets which in the mass resemble a clump of moss. Examine them individually and they will be found to be sometimes mejre filaments of cells sometimes thin"T translucent, heart-shaped plates of cells attached to the soil by root-like hairs. If kept moist by occasional sprinklings, of water they develop to .the next stages marked by the appearance, j from underneath the plantlet.. of a leaf of sturdier texture, /which grows apace and shows a decided resemblance to the parent fern. It is well known that the first leaf of a seedling rarely resembles the mature ones, and it is natural to regard the little* plant that grows from the spore, as the seed-leaf of the fern. It may at once be stated .that this is not.the case. The plantlet or prothallus as it is called, stands hi a similar relation to the tern that a butterfly does to a caterpillar;- that is to say, the prothallus is produced asexually from the fern, and, to complete the cycle, a fern arises from a fertilised egg upon the prothallus. To verify these facts requires patient work with the microscope, but some of the points may be easily made out with the aid of a low power. Place one or. two prothalli upside down upon the glass slide, and a little search will reveal the boule-shaped organs that contain the eggs. The spherical autheridia filled with the male fertilising speriuatozoids are a little less easy to spot. If the prothalli be. covered with a drop of water one may be lucky enough to see,one of these autheridia split open, setting free the active spermatozoids. They swim about by means of delicate scilia until they come close to the mouth of the organ, iii which the egg lies. Into this they are drawn as by a magnet, and 'immediately fusion of the egg with one sperniatozoid takes place. The egg then begins to segment, ana finally grows into an embryo, ' which at first is dependent upon the prothallus for its nourishment, but later puts out roots and leaf of its own. It quickly outgrows tts parent in size; and the latter, becoming at, length like a mere scale beside its giant progeny, shrivels up fend dies. It will be clear that the stage in the life of a fern whiclf corresponds to the pollinating of a flower is not the spore-bearing stage, but the moment when the egg formed on the prothallus is fertilised by the spermatoaoid. * ' +T.There is a Pror°lln^y interesting theory that a plant or animal repeats in its individual life the history of its race, or, as Sir J. Arthur Thomson puts it, "climbs its own genealogical tree." For example, "the familiar development of frog-soawn into tadpoles and froglings is in some respects almost startling in its recapitulation of the evolution of the amphibian race ; from fish ancestors." According to ■■ this theory the development of the*fern through all its stages should give us hints concerning the evolution of the race of plants to which it belongs. Let us glance once again at the germinating spore. It first forms a thread of cells strongly resembling the, j simplest kinds of sea weeds and those . green algae which are commonly found •; m ponds, water-troughs, and clinging .to stones in running streams. There j is, a great accumulation of evidence ;to show that the remote ancestors of | ferns—and of. flowering* plants as well —were just such simple aquatic forms as these. They must, in course of time, have gradually adapted them- ■ selves to a land life; but never com-! petely, for, as we have seen, there is always one moment in the life of the fern, even the bracken on the dry moor, when its continued existence deypends upon a drop of water—the drop that enables the spermatozoid to swim Id, the egg. To that extent the fern

Is still an aquatic. Flowering plants, a much later form of evolution, have found a way of dispensing with even so much external water. It will be already wear why, of the two fern generations, the prothallus is usually referred to as the sexual, and the mature ferri as the asexual plant. Among the primitive aquatic plants from whose prototypes the ferns are supposed to be derived there are also found sexual_and asexual generations, and it wouiu appear that it was the latter which was able to adapt itself to a sub-aerial life. The other lagged behind, handicapped by its need for water and has remained the same unattractive thing it originally was, a filament or plate of simple tells. The asexual plant has been modified in countless ways, culminating in such superb forms as the giant Todea and Dicksonia of the New Zealand bush. "The Origin of a Land Flora," by Pjrofessor Brown, of Glasgow Univer- , sity, may be referred to as an interesting attempt to outline a possible line of descent., Unfortunately, the fossil remains of plants help little to elucidate the .problem. The kind of plants which would presumably be the ancestors of the ferns were, like mosses, liverworts and algae, too delicate in texture to resist disintegration while the petrifying agencies got to work. The testimony of the rocks is given, however, on another and as interesting a subject—namely, the evolutionary connection between ferns and flowering plants. Fossils of intermediate forms are preserved with wonderful completeness, showing internal structure almost as clearly as a living plant. Those interested in the subject will find it dealt with in Dr. Scott's "Studies in Fossil Botany,'' where no fewer than three divisions, of fossil fern-like plants are described as transitional between true ferns and primitive seed-plants of the fir and araucaria types. Fortunately ferns have heen so well adapted to their environment that they have not, while giving rise t onewe'r forms, themselves become * extinct. They' remain what, they have been since the. early ages of the world's history, aristocrats of plant life and most beautiful withal. i '