PAST HISTORIES OF PLANT FAMILIES VI. The Ferns
Unfortunately the records in the rocks do not go back so far as to touch what must have been the most interesting period in the history of the ferns, namely, the point where they diverged from some simple ancestral type, or at least were sufficiently primitive to give indications of their origin from some lower group.
Before the Devonian period all plant impressions are of little value, and by that early pre-Carboniferous time there are preserved complex leaves, which are to all appearance highly organized ferns.
Today the dominant family in this group is the Polypodiaceæ. It includes nearly all our British ferns, and the majority of species for the whole world. This family does not appear to be very old, however, and it cannot be recognized with certainty beyond Mesozoic times.
From the later Mesozoic we have only material in the form of impressions, from which it is impossible to draw accurate conclusions unless the specimens have sporangia attached to them, and this is not often the case. The cuticle of the epidermis or the spores can sometimes be studied under the microscope after special treatment, but on the whole we have very little information about the later Mesozoic ferns.
A couple of specimens from the older Mesozoic have been recently described, with well-preserved structure, and they belong to the family of the Osmundas (the so-called “flowering ferns”, because of the appearance of special leaves on which all the sporangia are crowded), and show in the anatomical characters of their stems indications that they may be related to an old group, the Botryopterideæ, in which are the most important of the Palæozoic ferns.
In the Palæozoic rocks there are numerous impressions as well as fern petrifactions, but in the majority of cases the connection between the two is not yet established. There were two main series of ferns, which may be classed as belonging to
Of these the former has still living representatives, though the group is small and unimportant compared with what it once was; the latter is entirely extinct, and is chiefly developed in the Carboniferous and succeeding Permian periods.
The latter group is also the more interesting, for its members show great variety, and series may be made of them which seem to indicate the course taken in the advance towards the Pteridosperm type. For this reason the group will be considered first, while the structure of the Pteridosperms is still fresh in our minds.
The Botryopterideæ formed an extensive and elaborate family, with its numerous members of different degrees of complexity. There is, unfortunately, but little known as to their external appearance, and almost no definite information about their foliage. They are principally known by the anatomy of their stems and petioles. Some of them had upright trunks like small tree ferns (living tree ferns belong to quite a different family, however), others appear to have had underground stems, and many were slender climbers.
In their anatomy all the members of the family have monostelic structure. This is noteworthy, for at the present time though a number of genera are monostelic, no family whose members reach any considerable size or steady growth is exclusively monostelic. In the shape of the single stele, there is much variety in the different genera, some having it so deeply lobed that only a careful examination enables one to recognize its essentially monostelic nature. In fig. 86 a radiating star-shaped type is illustrated. Between this elaborate type of protostele in Asterochlaena, and the simple solid circular mass seen in Botryopteris itself (fig. 88) are all possible gradations of structure.
In several of the genera the center of the wood is not entirely solid, but has cells of soft tissue, an incipient pith, mixed with scattered tracheids, as in fig. 87.
In most of the genera numerous petioles are given off from the main axis, and these are often of a large size compared with it, and may sometimes be thicker than the axis itself. Together with the petiole usually come off adventitious roots, as is seen in fig. 88, which shows the main axis of a Botryopteris. The petioles of the group show much variety in their structure, and some are extremely complex. A few of the shapes assumed by the steles of the petioles are seen in fig. 89; they are not divided into separate bundles in any of the known forms, as are many of the petiole steles of other families.
In one genus of the family secondary wood has been observed. This is highly suggestive of the condition of the stele in Heterangium, where the large mass of the primary wood is surrounded by a relatively small quantity of secondary thickening, developed in normal radial rows from a cambium.
Another noteworthy point in the wood of these plants is the thickening of the walls of the wood cells. Many of them have several rows of bordered pits, and are, individually, practically indistinguishable from those of the Pteridosperms, cf. fig. 81 and fig. 90. These are unlike the characteristic wood cells of modern ferns and of the other family of Palæozoic ferns.
The foliage of most members of the family is unknown, or at least, of the many impressions which possibly belong to the different genera, the most part have not yet been connected with their corresponding structural material. There are indications, however, that the leaves were large and complexly divided.
The fructifications were presumably fern sporangia of normal but rather massive type. Of most genera they are not known, though in a few they have been found in connection with recognizable parts of their tissue. The best known of the sporangia are large, in comparison with living sporangia (actually about 2.5 millimetres long), oval sacs clustered together on little pedicels. The spores within them seem in no way essentially different from normal fern spores.
The coexistence of the Botryopterideæ and Pteridosperms, and the several points in the structure of the former which seem to lead up to the characters of the latter group, are significant. The Botryopterideæ, even were they an entirely isolated group, would be interesting from the variety of structures and the variations of the monostele in their anatomy; and the prominent place they held in the Palæozoic flora, as the greatest family of ferns of that period, gives them an important position in fossil botany.
The other family of importance in Palæozoic times, the Marattiaceæ, has descendants living at the present day, though the family is now represented by a small number of species belonging to but five genera which are confined to the tropics. Perhaps the best known of these is the giant “Elephant Fern”, which sends up from its underground stock huge complex fronds ten or a dozen feet high. Other species are of the more usual size and appearance of ferns, while some have sturdy trunks above-ground supporting a crown of leaves. The members of this family have a very complex anatomy, with several series of steles of large size and irregular shape. Their fructifications are characteristic, the sporangia being placed in groups of about five to a dozen, and fused together instead of ripening as separate sacs as in the other fern families.
Impressions of leaves with this type of sorus (group of fern sporangia) are found in the Mesozoic rocks, and these bridge over the interval between the living members of the family and those which lived in Palæozoic times.
In the Coal Measure and Permian periods these plants flourished greatly, and there are remains of very numerous species from that time. The family was much more extensive then than it is now, and the individual members also seem to have reached much greater dimensions, for many of them had the habit of large tree ferns with massive trunks. Up till Triassic times half of the ferns appear to have belonged to this family; since then, however, they seem to have dwindled gradually down to the few genera now existing.
On the Continent fossils of this type with well-preserved structure have long been known to the general public, as their anatomy gave the stones a very beautiful appearance when polished, so that they were used for decorative purposes by lapidaries before their scientific interest was recognized.
The members of the Palæozoic Marattiaceæ which have structure preserved generally go by the generic name Psaronius, in which there is a great number of species. They show considerable uniformity in their essential structure (in which they differ noticeably from the group of ferns just described), so that but one type will be considered.
In external appearance they probably resembled the “tree ferns” of the present day (though these belong to an entirely different family), with massive stumps, some of which reached a height of 60 ft. The large spreading leaves were arranged in various ways on the stem, some in a double row along it, as is seen by the impressions of the leaf scars, and others in complex spirals. On the leaves were the spore sacs, which were in groups, some completely fused like those of the modern members of the family, and others with independent sporangia massed in well-defined groups. In their microscopic structure also they appear to have been closely similar to those of the living Marattiaceæ.
The transverse section of a stem shows the most characteristic and best-known view of the plant. This is shown in fig. 91, in somewhat diagrammatic form.
The mass of rootlets which entirely permeate and surround the outer tissues of the stem is a very striking and characteristic feature of all the species of Psaronius. Though such a mass of roots is not found in the living species, yet the microscopic structure of an individual fossil root is almost identical with that of a living Marattia.
Though these plants were so successful and so important in Palæozoic times, the group even then seems to have possessed little variety and little potentiality for advance in new directions. They stand apart from the other fossils, and the few forms which now compose the living Marattiaceæ are isolated from the present successful types of modern ferns. From the Psaronieæ we can trace no development towards a modern series of plants, no connection with another important group in the past. They appear to have culminated in the later Palæozoic and to have slowly dwindled ever since. It has been suggested that the male fructifications of the Bennettiteæ and the Pteridosperms show some likeness to the Marattiaceæ, but there does not seem much to support any view of phylogenetic connection between them.
Before leaving the palæozoic ferns, mention should be made of the very numerous leaf impressions which seem to show true fern characters, though they have not been connected with material showing their internal structure. Among them it is rare to get impressions with the sori or sporangia, but such are known and are in themselves enough to prove the contention that true ferns existed in the Palæozoic epoch. For it might be mentioned as a scientific curiosity, that after the discovery that so many of the leaf impressions which had always been supposed to be ferns, really belonged to the seed-bearing Pteridosperms, there was a period of panic among some botanists, who brought forward the startling idea that there were no ferns at all in the Palæozoic periods, and that modern ferns were degenerated seed-bearing plants!
These two big groups from the Palæozoic include practically all the ferns that then flourished. They have been spoken of (together with a few other types of which little is known) as the Primofilices, a name which emphasizes their primitive characters. As can be seen by the complex organization of the genera, however, they themselves had advanced far beyond their really primitive ancestors. There is clear indication that the Botryopterideæ were in a period of change, what might almost be termed a condition of flux, and that from their central types various families separated and specialized. Behind the Botryopterideæ, however, we have no specimens to show us the connection between them and the simpler groups from which they must have sprung. From a detailed comparative study of plant anatomy we can deduce some of the essential characters of such ancestral plants, but here the realm of fossil botany ceases, to give place to theoretical speculation. As a fact, there is a deep abyss between the ferns and the other families of the Pteridophytes, which is not yet bridged firmly enough for any but specialists, used to the hazardous footing on such structures, to attempt to cross it. Until the buttresses and pillars of the bridge are built of the strong stone of fossil structures we must beware of setting out on what would prove a perilous journey.
In the Coal Measures and previous periods we see the ferns already represented by two large families, differing greatly from each other, and from the main families of modern ferns which sprung at a later date from some stock which we have not yet recognized. But though their past is so obscure, the palæozoic ferns and their allies throw a brilliant light on the course of evolution of the higher groups of plants, and the gulf between ferns and seed-bearing types may be said to be securely bridged by the Botryopterideæ and the Pteridosperms.
GARDEN AND FOREST
Volume 1, Number 1
NEW YORK, WEDNESDAY, FEBRUARY 29, 1888.
Two Ferns and their Treatment.
Adiantum Farleyense.—This beautiful Maidenhair is supposed to be a subfertile, plumose form of A. tenerum, which much resembles it, especially in a young state. For decorative purposes it is almost unrivaled, whether used in pots or for trimming baskets of flowers or bouquets. It prefers a warm, moist house and delights in abundant water. We find it does best when potted firmly in a compost of two parts loam to one of peat, and with a good sprinkling of sifted coal ashes. In this compost it grows very strong, the fronds attaining a deeper green and lasting longer than when grown in peat. When the pots are filled with roots give weak liquid manure occasionally. This fern is propagated by dividing the roots and potting in small pots, which should be placed in the warmest house, where they soon make fine plants. Where it is grown expressly for cut fronds the best plan is to plant it out on a bench in about six inches of soil, taking care to give it plenty of water and heat, and it will grow like a weed.
Actiniopteris radiata.—A charming little fern standing in a genus by itself. In form it resembles a miniature fan palm, growing about six inches in height. It is generally distributed throughout the East Indies. In cultivation it is generally looked upon as poor grower, but with us it grows as freely as any fern we have. We grow a lot to mix in with Orchids, as they do not crowd at all. We pot in a compost of equal parts loam and peat with a few ashes to keep it open, and grow in the warmest house, giving at all times abundance of water both at root and overhead. It grows very freely from spores, and will make good specimens in less than a year. It is an excellent Fern for small baskets.
GARDEN AND FOREST
Volume 1, Number 1
NEW YORK, WEDNESDAY, FEBRUARY 29, 1888.
Horticultural Exhibitions in London.
At a late meeting of the floral committee of the Royal Horticultural Society at South Kensington among many novelties was a group of seedling bulbous Calanthes from the garden of Sir Trevor Lawrence, who has devoted much attention to these plants and has raised some interesting hybrids. About twenty kinds were shown, ranging in color from pure white to deep crimson. The only one selected for a first-class certificate was C. sanguinaria, with flowers similar in size and shape to those of C. Veitchii, but of an intensely deep crimson. It is the finest yet raised, surpassing C. Sedeni, hitherto unequaled for richness of color. The pick of all these seedlings would be C. sanguinaria, C. Veitchii splendens, C. lactea, C. nivea, and C. porphyrea. The adjectives well describe the different tints of each, and they will be universally popular when once they find their way into commerce.
Cypripedium Leeanum maculatum, also shown by Sir Trevor Lawrence, is a novelty of sterling merit. The original C. Leeanum, which is a cross between C. Spicerianum and C. insigne Maulei, is very handsome, but this variety eclipses it, the dorsal sepal of the flower being quite two and one-half inches broad, almost entirely white, heavily and copiously spotted with purple. It surpasses also C. Leeanum superbum, which commands such high prices. I saw a small plant sold at auction lately for fifteen guineas and the nursery price is much higher.
Lælia anceps Schrœderæ, is the latest addition to the now very numerous list of varieties of the popular L. anceps. This new form, to which the committee with one accord gave a first class certificate, surpasses in my opinion all the colored varieties, with the possible exception of the true old Barkeri. The flowers are of the average size and ordinary form. The sepals are rose pink, the broad sepals very light, almost white in fact, while the labellum is of the deepest and richest velvety crimson imaginable. The golden tipped crest is a veritable beauty spot, and the pale petals act like a foil to show off the splendor of the lip.
Two new Ferns of much promise received first class certificates. One named Pteris Claphamensis is a chance seedling and was found growing among a lot of other sporelings in the garden of a London amateur. As it partakes of the characters of both P. tremula and P. serrulata, old and well known ferns, it is supposed to be a natural cross between these. The new plant is of tufted growth, with a dense mass of fronds about six inches long, elegantly cut and gracefully recurved on all sides of the pot. It is looked upon by specialists as just the sort of plant that will take in the market. The other certificated fern, Adiantum Reginæ, is a good deal like A. Victoriæ and is supposed to be a sport from it. But A. Reginæ, while it has broad pinnæ of a rich emerald green like A. Victoriæ, has fronds from nine to twelve inches long, giving it a lighter and more elegant appearance. I don’t know that the Victoria Maidenhair is grown in America yet, but I am sure those who do floral decorating will welcome it as well as the newer A. Reginæ. A third Maidenhair of a similar character is A. rhodophyllum and these form a trio that will become the standard kinds for decorating. The young fronds of all three are of a beautiful coppery red tint, the contrast of which with the emerald green of the mature fronds is quite charming. They are warm green-house ferns and of easy culture, and are supposed to be hybrid forms of the old A. scutum.
Nerine Mansellii, a new variety of the Guernsey Lily, was one of the loveliest flowers at the show. From the common Guernsey Lily it differs only in color of the flowers. These have crimpled-edged petals of clear rose tints; and the umbel of flowers is fully six inches across, borne on a stalk eighteen inches high. These Guernsey Lilies have of recent years come into prominence in English gardens since so many beautiful varieties have been raised, and as they flower from September onward to Christmas they are found to be indispensable for the green-house, and indoor decoration. The old N. Fothergillii major, with vivid scarlet-crimson flowers and crystalline cells in the petals which sparkle in the sunlight like myriads of tiny rubies, remains a favorite among amateurs. Baron Schroeder, who has the finest collection in Europe, grows this one only in quantity. An entire house is filled with them, and when hundreds of spikes are in bloom at once, the display is singularly brilliant.
A New Vegetable, a Japanese plant called Choro-Gi, belonging to the Sage family, was exhibited. Its botanical name is Stachys tuberifera and it was introduced first to Europe by the Vilmorins of Paris under the name of Crosnes du Japon. The edible part of the plant is the tubers, which are produced in abundance on the tips of the wiry fibrous roots. These are one and a half inches long, pointed at both ends, and have prominent raised rings. When washed they are as white as celery and when eaten raw taste somewhat like Jerusalem artichokes, but when cooked are quite soft and possess the distinct flavor of boiled chestnuts. A dish of these tubers when cooked look like a mass of large caterpillars, but the Committee pronounced them excellent, and no doubt this vegetable will now receive attention from some of our enterprising seedsmen and may become a fashionable vegetable because new and unlike any common kind. The tubers were shown now for the first time in this country by Sir Henry Thompson, the eminent surgeon. The plant is herbaceous, dying down annually leaving the tubers, which multiply very rapidly. They can be dug at any time of the year, which is an advantage. The plant is perfectly hardy here and would no doubt be so in the United States, as it remains underground in winter. [A figure of this plant with the tubers appeared in the Gardener’s Chronicle, January 7th, 1888.—Ed.]
Phalænopsis F. L. Ames, a hybrid moth orchid, the result of intercrossing P. grandiflora of Lindley with P. intermedia Portei (itself a natural hybrid between the little P. rosea and P. amabilis), was shown at a later exhibition. The new hybrid is very beautiful. It has the same purplish green leaves as P. amabalis, but much narrower. The flower spikes are produced in the same way as those of P. grandiflora, and the flowers in form and size resemble those of that species, but the coloring of the labellum is more like that of its other parent. The sepals and petals are pure white, the latter being broadest at the lips. The labellum resembles that ofP. intermedia, being three-lobed, the lateral lobes are erect, magenta purple in color and freckled. The middle or triangular lobe is of the same color as the lateral lobes, but pencilled with longitudinal lines of crimson, flushed with orange, and with the terminal cirrhi of a clear magenta. The column is pink, and the crest is adorned with rosy speckles. The Floral Committee unanimously awarded a first-class certificate of merit to the plant.
A New Lælia named L. Gouldiana has had an eventful history. The representative of Messrs. Sander, of St. Albans, the great orchid importers, while traveling in America saw it blooming in New York, in the collection of Messrs. Siebrecht & Wadley, and noting its distinctness and beauty bought the stock of it. The same week another new Lælia flowered in England and was sent up to one of the London auction rooms for sale. As it so answered the description of the American novelty which Messrs. Sander had just secured it was bought for the St. Albans collection, and now it turns out that the English novelty and the American novelty are one and the same thing, and a comparison of dates shows that they flowered on the same day, although in different hemispheres. As, however, it was first discovered in the United States, it is intended to call it an American orchid, and that is why Mr. Jay Gould has his name attached to it, In bulb and leaf the novelty closely resembles L. albida, and in flower both L. anceps and L. autumnalis. The flowers are as large as those of an average form of L. anceps, the sepals are rather narrow, the petals as broad as those of L. anceps Dawsoni, and both petals and sepals are of a deep rose pink, intensified at the tips as if the color had collected there and was dripping out. The tip is in form between that of L. anceps and L. autumnalis and has the prominent ridges of the latter, while the color is a rich purple crimson. The black viscid pubescence, always seen on the ovary of L. autumnalis, is present on that of L. Gouldiana. The plants I saw in the orchid nursery at St. Albans lately, bore several spikes, some having three or four flowers. Those who have seen it are puzzled about its origin, some considering it a hybrid between L. anceps and L. autumnalis, others consider it a distinct species and to the latter opinion I am inclined. Whatever its origin may be, it is certain we have a charming addition to midwinter flowering orchids.
London, February 1st.