A. C. Seward

“ In certain parts of the world, as for example the north-west Highlands of Scotland, the Malvern Hills, Scandinavia, and in many other regions in Europe and North America, geologists have recognised what they believe to be the foundation stones of the world. These Archaean rocks, which underlie the oldest fossiliferous strata, belong to a period of geological evolution from which it appears to be hopeless to obtain any light as to the nature of the contemporary organic world. ”

“ If we pass beyond the stretch of time represented by the life of a single tree, a few successive generations suffice to carry our retrospect back to the days when forests of oaks, birches, and other trees impeded the progress of the Roman invaders, and, a stage farther back, to the age of Neolithic man whose remains are occasionally found in our heaths and moors and in the submerged forests round our coast. ”

“ Although most people are familiar with some of the commoner means by which plants are able to colonise new ground through the adaptation of their fruits and seeds to various methods of transport, the conception of a plant as a stationary organism tends to prevent due allowance being made for the comparative facility with which, in the course of successive generations, a species is able to wander from place to place. The individual animal is endowed with powers of locomotion enabling it to seek new feeding-grounds and to avoid enemies ”

“ It is customary to speak of the British flora as consisting for the most part of species introduced into this country by natural means, while some plants owe their introduction to human agency or are 'escapes' from cultivation. It is by no means an easy task in some instances to decide whether a species is native or introduced, but in some cases, a few of which are mentioned, there is no doubt as to the alien nature of the plants. ”

“ Many examples might be quoted from both the animal and plant kingdoms in support of the view that discontinuous distribution is a criterion of antiquity. When identical or very nearly identical plants occur in regions separated from one another by areas in which the particular species is unknown, the inference is either that the surviving individuals are remnants of a large number formerly distributed over a wider continuous area, or that in the course of evolution similar conditions in widely separated areas led to the production of identical types. ”

“ By cutting sections of these nodules and grinding them to a transparent thinness, the most delicate tissues of Carboniferous plants are rendered accessible to investigation under the high power of a microscope. As our attention is absorbed by the examination of the details of cell-structure it is easy to forget that the section has not been cut from a living plant, but from the twig of a tree which grew in the forests of the Coal age. ”

“ It is only in the minority of cases that the accidents of preservation of fragments of ancient floras have given us the means of investigating the internal structure of the plant organs. It is far more frequently the case that fossil plants are represented only by a carbonised film on the surface of a piece of shale or other rock: the actual substance of the plant has been converted into a thin layer of coal, and though the venation and other surface-features may be clearly revealed, the internal tissues have been destroyed. ”

“ For those who have neither the time nor the preliminary training to study great subjects on a grand scale these excellent handbooks seem specially designed. They have been written by scholars of eminence, and give in small compass an admirable epitome of the subjects with which they deal These little volumes represent the essence that the specialism of to-day can give to the people in popular form on the subjects dealt with. ”

“ Europe was much warmer than it is now, and long-before the beginning of the climatic changes which culminated in the Glacial period, there was a land-connexion between the west of Ireland and the south-west of the continent. Mr Praeger, whose work on the Irish flora is well known to systematic botanists, agrees with the conclusions of Forbes, and sees in the Portuguese and Mediterranean plants 'relics of a vegetation which once spread along a bygone European coast-line which stretched unbroken from Ireland to Spain' (23) . ”

“ It has long been recognised that several members of the British flora are related to Scandinavian « 22 » species. The Scandinavian flora, as Sir Joseph Hooker says in his well-known paper on the 'Outlines of the Distribution of Arctic plants,' 'not only girdles the globe in the Arctic Circle, and dominates over all others in the North Temperate Zone of the Old World, but intrudes conspicuously into every other temperate flora, whether in the northern or southern hemisphere, or on the Alps of tropical countries' (17) . ”

“ In the Rhaetic plant-beds of Northern and Central Europe, of North America, Tonkin, and elsewhere, numerous fossil leaves have been discovered which in shape, venation, and in the manner of occurrence of the sporangia bear a close resemblance to species of Dipteris. Ferns of this type were abundant in the Jurassic floras of the northern hemisphere, and it is interesting to find impressions of Dipteris-like leaves both in the Jurassic rocks of the Yorkshire coast as well as in slightly newer beds of the same geological period on the north-east coast of Sutherland. ”

“ A tree, unlike the higher animals, does not reach a stage at which the whole of its substance attains a condition of permanence and fixity. It consists of a complex branching-system in which each shoot increases in length by virtue of the youthful vigour of its apex: to a large extent the tree as a whole consists of lifeless material incapable of further growth, as is the case of the older portions of a coral-reef ”

“ The plants of the Palaeozoic period, though often differing considerably from those of the same class in the floras of to-day, exhibit a remarkably high type of organisation. Some of the most abundant trees in the forest of the Coal age are decidedly superior in the complexity of their structure, as also in size, to modern survivals of the same stock. On the other hand, it must be remembered that Monocotyledons and Dicotyledons which now occupy the highest place in the hierarchy of plants have left no sign of their existence in any of the Palaeozoic strata. ”

“ Similarly, the close agreement between existing plants and species which lived in remote epochs speaks of continuity through the ages, and bridges across an extent of time too great to be expressed by ordinary standards of measurement. Terms of years when extended beyond the limits to which our minds are accustomed cease to have any definite meaning. While there is a certain academic interest in discussions as to the age of the earth as expressed in years, we are utterly unable to realise the significance of the chronology employed. ”

“ The Ferns and other plants in which the male cells are motile, represent earlier stages in the progress of plant development, when the presence of water was essential for the act of fertilisation, a relic of earlier days when the whole plant-body was fitted for a life in water. As higher types were produced, the plant-machinery became less dependent on an aqueous habitat, and the loss of organs of locomotion in the male cells is an instance of the kind of change accompanying the gradual adaptation to life on land. ”

“ From Tertiary strata in the Isle of Wight, on the Hampshire coast, and in the London basin numerous fossil plants have been obtained, which afford convincing evidence of climatic conditions much more genial than those of the present day. The presence of palm leaves and of a wealth of other sub-tropical plants in Lower Tertiary beds in England reveals the existence of a flora differing considerably both from that in the uppermost Tertiary beds of Norfolk and from the modern British flora, but closely allied to the present Mediterranean flora. ”

“ One of the Sheppey fruits may be mentioned as an especially interesting sample of the early Tertiary flora, namely the genus Nipadites, so named from the very close resemblance of the fossils to the fruits of the existing tropical plant Nipa. Nipa fruticans, sometimes described as a stemless palm because of the absence of the erect stem which is usually a characteristic feature of palms, grows in brackish estuaries of many tropical countries (Fig. 5, A) : it has long leaves not unlike those of the date-palm and bears clusters of fruits as large as a man's head ”

“ Ancestors of Araucaria must have been common trees in the European vegetation in Jurassic and Lower Cretaceous periods, and even as late as the Tertiary period there is evidence that representatives of the family still lingered in the north. One conclusion which seems almost unavoidable is that the species of Araucaria and Agathis that survive, in some cases only in one or two small islands in the South Pacific, have in the course of successive ages wandered from the other end of the world. ”

“ There were occasional pauses in the volcanic activity, during which vegetation established itself on the weathered surface of the lava, and left traces of its existence in the leaves and twigs preserved in the sedimentary material enclosed between successive lava-floras. At Ardtun Head in the Isle of Mull beautifully preserved leaves of Ginkgo, 2-4 inches in breadth, with the median sinus and the venation characteristic of the leaves of the existing plant, have been discovered in a bed of clay which marks the site of a lake in a depression on the lava-plateau. ”

“ The more efficient protection of the ovules, the germs which, after fertilisation, become the seeds, the extraordinary variety in the floral mechanisms for assisting cross-pollination, the arrangements for nursing the embryo, and the structural features of the wood in relation both to rapid transport of water and to the storage of food, are factors which have probably contributed to the success of the Angiosperms. ”

“ Though hardy in England, it requires warmer summers for full development and regular flowering. To botanists this Eastern tree is of peculiar interest, partly because of the isolated position it occupies in the plant-kingdom and partly by reason of its great antiquity. There is probably no other existing tree which has so strong a claim to be styled a 'living fossil,' to use a term applied by Darwin to survivals from the past. ”

“ Others which flourished in a former period no longer survive, either themselves or in direct descendants. 'The extinction of species has been involved in the most gratuitous mystery.' We can only speculate vaguely as to the cause of success or failure. Certain types were better armed for the struggle for life, and produced descendants able to hold their own and to perpetuate the race through the ages in an unbroken line. Others had a shorter life and fell out of the ranks of the advancing and ever changing army. To quote Darwin's words:'We need not marvel at extinction ”

“ In the peat-beds of Scotland even up to 3000 feet above sea-level the stumps of pines occur in abundance, and in many places recent researches have revealed the occurrence of successive forests of pines, oaks, and spruces separated from one another by the accumulations of swampy vegetation (9) . The spruce fir has long ceased to be a member of the British flora, but in a few localities in the Scottish Highlands patches of primeval pine forests remain. ”