To the geologist and botanist the subject is one of importance with reference to their special pursuits, and one on which it has not been easy to find any convenient manual of information. It is hoped that its treatment in the present volume will also be found sufficiently simple and popular to be attractive to the general reader. In a work of so limited dimensions, detailed descriptions cannot be given, except occasionally by way of illustration; but references to authorities will be made in foot-notes, and certain details, which may be useful to collectors and students, will be placed in notes appended to the chapters, so as not to encumber the text. The illustrations of this work are for the most part original; but some of them have previously appeared in special papers of the author. J. W. D. _February, 1888._ CONTENTS. PAGE CHAPTER I. Preliminary Ideas of Geological Chronology and of the Classification of Plants 1 CHAPTER II. Vegetation of the Laurentian and Early Paleozoic--Questions as to Algæ 8 CHAPTER III. The Erian or Devonian Forests--Origin of Petroleum--The Age of Acrogens and Gymnosperms 45 CHAPTER IV. The Carboniferous Flora--Culmination of the Acrogens--Formation of Coal 110 CHAPTER V. The Flora of the Early Mesozoic--Reign of Pines and Cycads 175 CHAPTER VI. The Reign of Angiosperms in the Later Cretaceous and Early Tertiary or Kainozoic 191 CHAPTER VII. Plants from the Tertiary to the Modern Period 219 CHAPTER VIII. General Laws of Origin and Migrations of Plants--Relations of Recent and Fossil Floras 237 APPENDIX. I. Comparative View of Paleozoic Floras 273 II. Heer's Latest Statements on the Greenland Flora 281 III. Mineralisation of Fossil Plants 284 IV. General Works on Palæobotany 286 LIST OF ILLUSTRATIONS. PAGE