CHAPTER III YESTERDAY AND TO-DAY

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Although to most people the study of fossil botany may appear to be an uninviting pursuit, there can be no question as to the importance of the science. It is only in this way that we are able to appreciate the changes which have led up to the existing types of plants. Now the question of the past history of the Vascular Cryptogams is of very special interest in more ways than one. It is, of course, most fascinating to be able to discover what kinds of Ferns flourished, for instance, at the period when the coal deposits were being formed. But, even in a cursory description, it will be quite impossible to allow the matter to rest there. The story of the past, in the case of the Vascular Cryptogams, is closely interwoven with some of the most absorbing phases in the evolution of the Flowering Plants which are such a dominant feature on the earth at the present time.

Quite recently we have had to alter our views materially on the matter of the past history of the Ferns. Within the last few years it has been proved that a huge number of the fossil remains, belonging to the PalÆozoic formation at any rate, are not Ferns at all. They belonged to a very distinct race of plants altogether, known as Pteridosperms, even though they had a superficial resemblance to Ferns. After a large amount of patient research it has been demonstrated that these plants bore seeds. The method of flowering and seed-production was vastly different from that which is to be observed in the flowering plants of to-day. The male or pollen-bearing organs were produced straight on the foliage in much the same way as the sporangium of a true Fern is developed. In a similar manner the seeds were borne straight on to the leaf. In some general points these plants also bore a strong resemblance to the Ferns, and it was this which misled the early observers. Without a doubt these Pteridosperms were related to the Ferns, and probably at some remote period the two groups had a common ancestry. There is good reason for believing that at the same time these Pteridosperms were flourishing true Ferns were also well represented.

Now the interesting point about these Ferns is that they were not vastly different, in many ways, from the species which exist on the earth at the present time. Of course certain types, of which we have living examples, were more fully represented than is the case nowadays; on the other hand, some of our most widely distributed families seem to have been at rather a low stage in their history. As well, the remains evidence a large number of very simple species, which perhaps give us an idea of what the original Ferns were like. But on the whole there is nothing to show that our living Ferns are any more developed than the highest types which grew in the coal forests. In these far-away times there were Tree Ferns; but so there are, of course, at the present time.

The early botanists who strove to prove that Ferns were, so to speak, the last development before the Flowering Plants were not, perhaps, very far from the truth. It has been seen that during the period when the coal deposits were being formed there flourished side by side races of true Ferns and Fern-like plants which bore seeds—the Pteridosperms. The point has also been suggested that in all probability these two groups of plants had a common origin. With the coming of later times (the Cretaceous and Jurassic periods) there appeared the BennettiteÆ. These remarkable plants seem to have entirely taken the place of the Pteridosperms, and were an enormous advance towards the Flowering Plants of the present day. Only recently have the BennettiteÆ been properly described and their interesting features fully understood. We have a few representatives of this important group in the Cycads, plants bearing a superficial resemblance to Palms, but actually very different in all other ways. By the manner in which the reproductive organs are produced, and the way in which the scheme is carried out, these BennettiteÆ appear to be a half-way house between the cryptogams and the advanced flowering plants. The stamens bearing the pollen are produced on the fronds very much like the sporangia of Ferns. On the other hand, the seed-bearing structures are collected together into a sort of pistil. This was borne at the tip of the branches and ended their growth, just as happens in the case of Flowering Plants. For some reason which we cannot understand these BennettiteÆ seem to have fallen back in the race for supremacy, for the group is but poorly represented in our modern Cycads and a few allied plants. In all the world there are perhaps not more than about a dozen species, the sole survivors of a race which at one time dominated the world. There seems every reason for thinking that the Flowering Plants arose as an offshoot of the BennettiteÆ, and in some way secured an advantage which enabled them to arrive at their present position.

When we come to consider the past history of the Club Mosses the record is of a different nature to that of the Ferns. Nowadays the Club Mosses are not of great importance in the world, even though, as will be shown later, the number of species is considerable. But when we travel back to PalÆozoic times, particularly in the coal period, it is evident that these plants were represented by a number of very large and dominant families. Some of these early Club Mosses certainly came very near to rivalling the Flowering Plants. Probably the tendency of the world to become drier has had something to do with the decline, seeing that in all cases the fertilization is carried out under water. We may gather some idea of the importance of the Club Mosses in PalÆozoic times from the fact that in every part of the world where coal deposits have been examined great numbers of the fossil remains of these plants are always discovered. Many of these grew into large trees which were a hundred or more feet in height, sending out great branching shoots above and an enormous root system below.

From a botanical point of view there is no doubt that some of the Club Mosses, particularly those belonging to the family SelaginellaceÆ, have approached very nearly to the Flowering Plants. At the present time the existing species, the Selaginellas, bring us up to the very threshold of the dominant group. The lowest division of the Flowering Plants is the GymnospermÆ (which includes the Conifers), and it is interesting to note the points of similarity between a typical Gymnosperm and a Selaginella. To start away with, the Selaginella bears two kinds of spores, each of which in its development has a definite sex character. The smaller ones (microspores) are in their manner of production analogous to the pollen-grains of the Flowering Plant. The prothallus and the male organ (antheridium) are comparable to the special cell-group in the pollen-grain, whilst the spermatozoids approximate to the generative cells. In the larger spores (megaspores) these represent the embryo sac, and the sporangium in which they are produced closely approximates to the part containing the embryo sac in the Flowering Plant. The prothallus which arises from the megaspore in the Selaginella closely resembles the endosperm—a special tissue formed to feed the embryo in the case of flowering plants. The female organ (archegonium) and the cell which it produces are practically identical in both cases. Fossil remains have shown that some of the plants like Selaginella which flourished in PalÆozoic times seemed to have come very near to the production of seed. Thus one species which has been described shows a megaspore which was permanently within the sporangium, and which in its general development greatly resembled a fruit. It is, of course, impossible to give more than a very brief outline of some of the chief points in this highly important comparison between the Gymnosperm and the Selaginella. The author trusts that those of his readers who are interested will pursue the study in the admirable textbooks which are now available.

The Horsetails, like the Club Mosses, have had a very important past. Although they are few in number, as far as the species are concerned, they still retain many striking characteristics. Without a doubt the PalÆozoic Horsetails grew into giant plants, sending out branches and developing trunks which in some ways are comparable to those possessed by our trees at the present time. These great stems seem to have arisen from rhizomes which travelled about in the mud of the coal jungles. It is usual to refer to these PalÆozoic Horsetails as Calamites, owing to the fact that they were originally supposed to bear a resemblance to a reed (Calamus). In the later rocks, such as those which belong to the Jurassic and Triassic periods, occur the Equisetites, plants which were still of great size, but already in some respects showing signs of that decline which has culminated at the present day in the little group of plants which, were it not for a certain robustness of growth, would find it hard to maintain their position at all.

To complete our brief survey of the Vascular Cryptogams it is now necessary that we should review the position of these plants at the present time. Of course in number the Ferns are enormously in advance of all the other plants put together. In the whole world, there are not far short of seventy distinct genera, which include anything between three and four thousand species. The Ferns of the United Kingdom number not far short of fifty, and there are certain variations from the type which some folk are tempted to include as species. For some reasons which we cannot well understand, the Ferns alone amongst the Vascular Cryptogams have been able to hold their own in the world. It is probable that there are quite as many species, and that these are as varied, to-day as has ever been the case. The size of Ferns, as we have already seen, varies enormously. In the tropics and in Australasia there are Tree Ferns eighty feet in height, whilst with many of the Filmy Ferns the size is scarcely larger than that of Mosses. Owing to the fact that it is so necessary in the scheme of reproduction, the majority of Ferns are lovers of moisture. None the less, a few specimens have adapted themselves marvellously to drier conditions. Thus the Bracken will grow on the exposed hillside or cliff-top even where its rhizomes cannot carry the roots to a great amount of moisture. Some of the most interesting species of Ferns are those which grow on walls and rocks, where there is little dampness, during the summer at any rate. Many of these have adopted special devices to cope with drought, such as are to be seen in the Scaly Spleenwort. Here the underside of the frond is covered with hairy scales, and in dry weather the leaves roll up so that the well-protected underside is alone exposed to the sun. After all, however, Ferns are most at home where there is a comparatively deep shade with abundance of moisture. Many species which will grow in somewhat dry situations attain a much finer development under happier conditions.

Luckily many kinds of Ferns are still very common in the United Kingdom. Of course, in much-visited localities the ravages of the trippers have practically exterminated some interesting species in these particular districts. Naturally, one hardly expects to find the Royal Fern flourishing to any extent in the popular holiday haunts—none the less, there are still any number of places where this noble plant “grows like a weed.” The wise man does not talk about such things to his friends. Many of our most beautiful Ferns are saved even in much-frequented places on account of the fact that they grow out of reach. No doubt the graceful Trichomanes of South Ireland would long ago have been stamped out in the Killarney district, were it not for the fact that it often grows in situations which it is almost impossible for anyone to reach.

As far as number is concerned, the living Club Mosses represent a comparatively insignificant group when compared with the Ferns. In all the world there are probably not more than five or six hundred species. These are very widely distributed, and there is hardly any part which cannot offer at least a few species. We have five species of Lycopodium in the United Kingdom. All are rather local, though often enough they occur in great abundance in special localities. Only one (Lycopodium inundatum) ever occurs in lowland districts; all the rest must be looked for on highland moors. A few exotic Lycopodiums grow to a fair size, though this is largely due to the fact that their creeping stems straggle along the ground for a considerable distance. The Selaginellas are a much more important group as far as the world generally is concerned. There are certainly as many as four or five hundred species, and some of these assume almost a shrubby habit. A species from Borneo (S. grandis) is said to attain the height of two feet. In the United Kingdom we have but a single species of Selaginella—S. spinosa, an insignificant little plant. Many exotic kinds are frequently grown in greenhouses, so that a variety of species is within the reach of everybody.

Authorities vary as to the exact number of species which belong to the only genus of the Horsetail—Equisetum; the estimate is never higher than forty. Nearly all these plants are striking in appearance, and some are quite large. A tropical American species is said to attain the height of thirty feet, though this is not so remarkable when one considers that the plant has a climbing habit. In the United Kingdom we have at least eight distinct species. Some of these are exceedingly common, and owing to their vigorous growth will often hold their own against all comers. Indeed, the existing Horsetails are, to use a common expression, “putting up such a good fight” that it is certain they will continue to hold their own for many a long day. Unlike the Club Mosses, the Horsetails seem to be quite happy in the vicinity of towns, and are often seen at their best on railway embankments and in similar situations.

Although the Vascular Cryptogams played an important part in helping to build up our vast stores of coal, it is astonishing to note of what little direct economic value they are to mankind at the present time. In a few parts of the world, where the native races make little or no attempt at agriculture, the root-stocks of Ferns—often rich in starch—are eaten. Thus the Maoris of New Zealand and some of the South Sea Islanders secure a poor kind of sago from some of the Tree Ferns which grow in their districts. The Japanese use the growing tips of the Bracken as food. Years ago, Ferns used to be burnt for potash in this country, and their astringent properties naturally attracted the old-world pharmacist. They are practically useless as fodder on account of their bitter taste, and no animal—except, perhaps, the goat—would think of eating Ferns. In many cases, however, Bracken is used regularly as a bedding-down material for cattle.

Coming to the Club Mosses, it is even more difficult to find that they are of any direct benefit. Some kinds in South America are said to yield a blue dye. Our Common Club Moss is in its huge quantity of spores responsible for the “Lycopodium Powder” which at one time was employed in the making of fireworks. The powder is said to be highly inflammable, but when shaken straight out of the cones it does not always ignite very readily. One of the Horsetails, the Dutch Rush (Equisetum hyemale), was—and perhaps is still—used in polishing, owing to the large amount of silica which is present in its stems. In addition, those who are interested in coast erosion say that the stronger-growing species of Equisetum should be planted to keep clay cliffs from falling. From an ornamental point of view the Ferns and some of the Club Mosses are, of course, of great value. They are widely cultivated in garden and greenhouse, and we may say that these plants make up in Æsthetic value what they lack from an economic point of view.

                                                                                                                                                                                                                                                                                                           

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