Read Ebook: Note sur une Méthode pour la Réduction d'Intégrales Définies et sur son Application à Quelques Formules Spécials by Haan D Bierens De David Bierens

Font size: 10 px 15 px 20 px 25 px 30 px 35 px

Background color: BlackWhiteGrayLight GrayDark GrayDim Gray

Text color: BlackWhiteGrayLight GrayDark GrayDim Gray

Apply/Save settings

Ebook has 83 lines and 12974 words, and 2 pages

PAGE

Preliminary Ideas of Geological Chronology and of the Classification of Plants 1

Vegetation of the Laurentian and Early Paleozoic--Questions as to Algae 8

The Erian or Devonian Forests--Origin of Petroleum--The Age of Acrogens and Gymnosperms 45

The Carboniferous Flora--Culmination of the Acrogens--Formation of Coal 110

The Flora of the Early Mesozoic--Reign of Pines and Cycads 175

The Reign of Angiosperms in the Later Cretaceous and Early Tertiary or Kainozoic 191

Plants from the Tertiary to the Modern Period 219

General Laws of Origin and Migrations of Plants--Relations of Recent and Fossil Floras 237

PAGE

Table of Chronology of Plants Protannularia Harknessii 21 Nematophyton Logani 22, 23 Trail of King-Crab 28 Trail of Carboniferous Crustacean 28 Rusichnites 29 Palaeophycus 30 Astropolithon 31 Carboniferous Rill-mark 33 Cast of Shrinkage Cracks 34 Cone-in-cone 36 Buthotrephis 37 Silurian Vegetation 40 Erian Plants 49 Protosalvinia 54 Ptilophyton 62, 63 Psilophyton 64, 66 Sphenophyllum 65 Lepidodendron 66 Various Ferns 72, 73 Archaeopteris 74 Caulopteris 75 Megalopteris 76 Calamites 77 Asterophyllites 78 Dadoxylon 79 Cordaites 81 Erian Fruits 82 Foliage from the Coal-formation 111 Sigillariae 112-114 Stigmariae 115 Vegetable Tissues 117 Coals and Erect Trees 118, 119 Lepidodendron 120 Lepidophloios 121 Asterophyllites, &c. 122 Calamites 123-125 Ferns of the Coal-formation 126-129 Noeggerathia dispar 130 Cordaites 131 Fruits of Cordaites, &c. 132 Conifers of the Coal-formation 135 Trigonocarpum 136 Sternbergia 137 Walchia imbricatula 138 Foliage of the Jurassic Period 177 Podozamites 178 Salisburia 180 Sequoia 181 Populus primaeva 191 Stercalia and Laurophyllum 194 Vegetation of the Cretaceous Period 195 Platanus 198 Protophyllum 199 Magnolia 200 Liriodendron 201 Brasenia 207 Gaylussaccia resinosa 228 Populus balsamifera 229 Fucus 230

THE

GEOLOGICAL HISTORY OF PLANTS.

PRELIMINARY IDEAS OF GEOLOGICAL CHRONOLOGY AND OF THE CLASSIFICATION OF PLANTS.

The knowledge of fossil plants and of the history of the vegetable kingdom has, until recently, been so fragmentary that it seemed hopeless to attempt a detailed treatment of the subject of this little book. Our stores of knowledge have, however, been rapidly accumulating in recent years, and we have now arrived at a stage when every new discovery serves to render useful and intelligible a vast number of facts previously fragmentary and of uncertain import.

The writer of this work, born in a district rich in fossil plants, began to collect and work at these as a boy, in connection with botanical and geological pursuits. He has thus been engaged in the study of fossil plants for nearly half a century, and, while he has published much on the subject, has endeavoured carefully to keep within the sphere of ascertained facts, and has made it a specialty to collect, as far as possible, what has been published by others. He has also enjoyed opportunities of correspondence or personal intercourse with most of the more eminent workers in the subject. Now, in the evening of his days, he thinks it right to endeavour to place before the world a summary of facts and of his own matured conclusions--feeling, however, that nothing can be final in this matter; and that he can only hope to sketch the present aspect of the subject, and to point the way to new developments, which must go on long after he shall have passed away.

The subject is one which has the disadvantage of presupposing some knowledge of the geological history of the earth, and of the classification and structures of modern plants; and in order that all who may please to read the following pages may be placed, as nearly as possible, on the same level, this introductory chapter will be devoted to a short statement of the general facts of geological chronology, and of the natural divisions of the vegetable kingdom in their relations to that chronology.

The crust of the earth, as we somewhat modestly term that portion of its outer shell which is open to our observation, consists of many beds of rock superimposed on each other, and which must have been deposited successively, beginning with the lowest. This is proved by the structure of the beds themselves, by the markings on their surfaces, and by the remains of animals and plants which they contain; all these appearances indicating that each successive bed must have been the surface before it was covered by the next.

As these beds of rock were mostly formed under water, and of material derived from the waste of land, they are not universal, but occur in those places where there were extensive areas of water receiving detritus from the land. Further, as the distinction of land and water arises primarily from the shrinkage of the mass of the earth, and from the consequent collapse of the crust in some places and ridging of it up in others, it follows that there have, from the earliest geological periods, been deep ocean-basins, ridges of elevated land, and broad plateaus intervening between the ridges, and which were at some times under water, and at other times land, with many intermediate phases. The settlement and crumpling of the crust were not continuous, but took place at intervals; and each such settlement produced not only a ridging up along certain lines, but also an emergence of the plains or plateaus. Thus at all times there have been ridges of folded rock constituting mountain-ranges, flat expansions of continental plateau, sometimes dry and sometimes submerged, and deep ocean-basins, never except in some of their shallower portions elevated into land.

Let us now tabulate the whole geological succession with the history of animals and plants associated with it:

ANIMALS. SYSTEMS OF FORMATIONS. PLANTS.

Age of Man and Mammalia.

Kainozoic. { Modern, { Pleistocene, Angiosperms and { Pliocene, Palms dominant. { Miocene, { Eocene.

Age of Reptiles.

Mesozoic. { Cretaceous, Cycads and Pines { Jurassic, dominant. { Triassic.

Age of Amphibians and Fishes. Age of Invertebrates.

Palaeozoic. { Permian, Acrogens and { Carboniferous, Gymnosperms { Erian, dominant. { Silurian, { Ordovician, { Cambrian, { Huronian .

Age of Protozoa.

Eozoic. { Huronian , Protogens and Algae. { Upper Laurentian, { Middle Laurentian, { Lower Laurentian.

It will be observed, since only the latest of the systems of formations in this table belongs to the period of human history, that the whole lapse of time embraced in the table must be enormous. If we suppose the modern period to have continued for say ten thousand years, and each of the others to have been equal to it, we shall require two hundred thousand years for the whole. There is, however, reason to believe, from the great thickness of the formations and the slowness of the deposition of many of them in the older systems, that they must have required vastly greater time. Taking these criteria into account, it has been estimated that the time-ratios for the first three great ages may be as one for the Kainozoic to three for the Mesozoic and twelve for the Palaeozoic, with as much for the Eozoic as for the Palaeozoic. This is Dana's estimate. Another, by Hull and Houghton, gives the following ratios: Azoic, 34?3 per cent.; Palaeozoic, 42?5 per cent.; Mesozoic and Kainozoic, 23?2 per cent. It is further held that the modern period is much shorter than the other periods of the Kainozoic, so that our geological table may have to be measured by millions of years instead of thousands.

We cannot, however, attach any certain and definite value in years to geological time, but must content ourselves with the general statement that it has been vastly long in comparison to that covered by human history.

Bearing in mind this great duration of geological time, and the fact that it probably extends from a period when the earth was intensely heated, its crust thin, and its continents as yet unformed, it will be evident that the conditions of life in the earlier geologic periods may have been very different from those which obtained later. When we further take into account the vicissitudes of land and water which have occurred, we shall see that such changes must have produced very great differences of climate. The warm equatorial waters have in all periods, as superficial oceanic currents, been main agents in the diffusion of heat over the surface of the earth, and their distribution to north and south must have been determined mainly by the extent and direction of land, though it may also have been modified by the changes in the astronomical relations and period of the earth, and the form of its orbit. We know by the evidence of fossil plants that changes of this kind have occurred so great as, on the one hand, to permit the plants of warm temperate regions to exist within the Arctic Circle; and, on the other, to drive these plants into the tropics and to replace them by Arctic forms. It is evident also that in those periods when the continental areas were largely submerged, there might be an excessive amount of moisture in the atmosphere, greatly modifying the climate, in so far as plants are concerned.

Croll, "Climate and Time."

Let us now consider the history of the vegetable kingdom as indicated in the few notes in the right-hand column of the table.

The most general subdivision of plants is into the two great series of Cryptogams, or those which have no manifest flowers, and produce minute spores instead of seeds; and Phaenogams, or those which possess flowers and produce seeds containing an embryo of the future plant.

The Cryptogams may be subdivided into the following three groups:

The Phaenogams are all vascular, but they differ much in the simplicity or complexity of their flowers or seeds. On this ground they admit of a twofold division:

It is this historical development that we have to trace in the following pages, and it will be the most simple and at the same time the most instructive method to consider it in the order of time.

VEGETATION OF THE LAURENTIAN AND EARLY PALAEOZOIC--QUESTIONS AS TO ALGAE.

The carbon thus occurring in the Laurentian is not to be regarded as exceptional or rare, but is widely distributed and of large amount. In Canada more especially the deposits are very considerable.

The graphite of the Laurentian of Canada occurs both in beds and in veins, and in such a manner as to show that its origin and deposition are contemporaneous with those of the containing rock. Sir William Logan states that "the deposits of plumbago generally occur in the limestones or in their immediate vicinity, and granular varieties of the rock often contain large crystalline plates of plumbago. At other times this mineral is so finely disseminated as to give a bluish-grey colour to the limestone, and the distribution of bands thus coloured seems to mark the stratification of the rock." He further states: "The plumbago is not confined to the limestones; large crystalline scales of it are occasionally disseminated in pyroxene rock, and sometimes in quartzite and in feldspathic rocks, or even in magnetic oxide of iron." In addition to these bedded forms, there are also true veins in which graphite occurs associated with calcite, quartz, orthoclase, or pyroxene, and either in disseminated scales, in detached masses, or in bands or layers "separated from each other and from the wall-rock by feldspar, pyroxene, and quartz." Dr. Hunt also mentions the occurrence of finely granular varieties, and of that peculiarly waved and corrugated variety simulating fossil wood, though really a mere form of laminated structure, which also occurs at Warrensburg, New York, and at the Marinski mine in Siberia. Many of the veins are not true fissures, but rather constitute a network of shrinkage cracks or segregation veins traversing in countless numbers the containing rock, and most irregular in their dimensions, so that they often resemble strings of nodular masses. It is most probable that the graphite of the veins was originally introduced as a liquid or plastic hydrocarbon; but in whatever way introduced, the character of the veins indicates that in the case of the greater number of them the carbonaceous material must have been derived from the bedded rocks traversed by these veins, to which it bears the same relation with the veins of bitumen found in the bituminous shales of the Carboniferous and Silurian rocks. Nor can there be any doubt that the graphite found in the beds has been deposited along with the calcareous matter or muddy and sandy sediment of which these beds were originally composed.

"Geology of Canada," 1863.

Paper by the author on Laurentian Graphite, "Journal of London Geological Society," 1876.

Matthew in "Quarterly Journal of the Geological Society," vol. xxi., p. 423. "Acadian Geology," p. 662.

It may fairly be assumed that in the present world, and in those geological periods with whose organic remains we are more familiar than with those of the Laurentian, there is no other source of unoxidized carbon in rocks than that furnished by organic matter, and that this has obtained its carbon in all cases, in the first instance, from the deoxidation of carbonic acid by living plants. No other source of carbon can, I believe, be imagined in the Laurentian period. We may, however, suppose either that the graphitic matter of the Laurentian has been accumulated in beds like those of coal, or that it has consisted of diffused bituminous matter similar to that in more modern bituminous shales and bituminous and oil-bearing limestones. The beds of graphite near St. John, some of those in the gneiss at Ticonderoga in New York, and at Lochaber and Buckingham, and elsewhere in Canada, are so pure and regular that one might fairly compare them with the graphitic coal of Rhode Island. These instances, however, are exceptional, and the greater part of the disseminated and vein graphite might rather be likened in its mode of occurrence to the bituminous matter in bituminous shales and limestones.

We may compare the disseminated graphite to that which we find in those districts of Canada in which Silurian and Devonian bituminous shales and limestones have been metamorphosed and converted into graphitic rocks not very dissimilar to those in the less altered portions of the Laurentian. In like manner it seems probable that the numerous reticulating veins of graphite may have been formed by the segregation of bituminous matter into fissures and planes of least resistance, in the manner in which such veins occur in modern bituminous limestones and shales. Such bituminous veins occur in the Lower Carboniferous limestone and shale of Dorchester and Hillsborough, New Brunswick, with an arrangement very similar to that of the veins of graphite; and in the Quebec rocks of Point Levi, veins attaining to a thickness of more than a foot, are filled with a coaly matter having a transverse columnar structure, and regarded by Logan and Hunt as an altered bitumen. These palaeozoic analogies would lead us to infer that the larger part of the Laurentian graphite falls under the second class of deposits above mentioned, and that, if of vegetable origin, the organic matter must have been thoroughly disintegrated and bituminised before it was changed into graphite. This would also give a probability that the vegetation implied was aquatic, or at least that it was accumulated under water.

Granby, Melbourne, Owl's Head, &c., "Geology of Canada," 1863, p. 599.

Dr. Hunt has, however, observed an indication of terrestrial vegetation, or at least of suba?rial decay, in the great beds of Laurentian iron-ore. These, if formed in the same manner as more modern deposits of this kind, would imply the reducing and solvent action of substances produced in the decay of plants. In this case such great ore-beds as that of Hull, on the Ottawa, seventy feet thick, or that near Newborough, two hundred feet thick, must represent a corresponding quantity of vegetable matter which has totally disappeared. It may be added that similar demands on vegetable matter as a deoxidising agent are made by the beds and veins of metallic sulphides of the Laurentian, though some of the latter are no doubt of later date than the Laurentian rocks themselves.

"Geology of Canada," 1863.

It would be very desirable to confirm such conclusions as those above deduced by the evidence of actual microscopic structure. It is to be observed, however, that when, in more modern sediments, Algae have been converted into bituminous matter, we cannot ordinarily obtain any structural evidence of the origin of such bitumen, and in the graphitic slates and limestones derived from the metamorphosis of such rocks no organic structure remains. It is true that, in certain bituminous shales and limestones of the Silurian system, shreds of organic tissue can sometimes be detected, and in some cases, as in the Lower Silurian limestone of the La Cloche Mountains in Canada, the pores of brachiopodous shells and the cells of corals have been penetrated by black bituminous matter, forming what may be regarded as natural injections, sometimes of much beauty. In correspondence with this, while in some Laurentian graphitic rocks, as, for instance, in the compact graphite of Clarendon, the carbon presents a curdled appearance due to segregation, and precisely similar to that of the bitumen in more modern bituminous rocks, I can detect in the graphitic limestones occasional fibrous structures which may be remains of plants, and in some specimens vermicular lines, which I believe to be tubes of Eozoon penetrated by matter once bituminous, but now in the state of graphite.

When palaeozoic land-plants have been converted into graphite, they sometimes perfectly retain their structure. Mineral charcoal, with structure, exists in the graphitic coal of Rhode Island. The fronds of ferns, with their minutest veins perfect, are preserved in the Devonian shales of St. John, in the state of graphite; and in the same formation there are trunks of Conifers in which the material of the cell-walls has been converted into graphite, while their cavities have been filled with calcareous spar and quartz, the finest structures being preserved quite as well as in comparatively unaltered specimens from the coal-formation. No structures so perfect have as yet been detected in the Laurentian, though in the largest of the three graphitic beds at St. John there appear to be fibrous structures, which I believe may indicate the existence of land-plants. This graphite is composed of contorted and slickensided laminae, much like those of some bituminous shales and coarse coals; and in these are occasional small pyritous masses which show hollow carbonaceous fibres, in some cases presenting obscure indications of lateral pores. I regard these indications, however, as uncertain; and it is not as yet fully ascertained that these beds at St. John are on the same geological horizon with the Lower Laurentian of Canada, though they certainly underlie the Primordial series of the Acadian group, and are separated from it by beds having the character of the Huronian.

Share on: WhatsApp @Hash Facebook Tweet