I. COMPARATIVE VIEW OF PALEOZOIC FLORAS II. HEER'S LATEST STATEMENTS ON THE GREENLAND FLOR Rusichnites Palæophycus Astropolithon. Carboniferous Rill-mark. Cone-in-cone Silurian Vegetation. Protosalvinia Ptilophyton (two Figures) Sphenophyllum (Frontispiece.) PAGE Lepidodendron Various Ferns. Archæopteris Caulopteris Megalopteris Calamites Asterophyllites Dadoxylon 65 66 72, 73 74 75 76 77 78 79 THE GEOLOGICAL HISTORY OF PLANTS. CHAPTER I. 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 ་་ B the more eminent workers in the subject. evening of his days, he thinks it right to place before the world a summary of facts a matured conclusions-feeling, however, tha be final in this matter; and that he can sketch the present aspect of the subject, and way to new developments, which must go he shall have passed away. The subject is one which has the disadva supposing some knowledge of the geologi the earth, and of the classification and struc ern plants; and in order that all who may the following pages may be placed, as nearl on the same level, this introductory chapt voted to a short statement of the general fact chronology, and of the natural divisions of kingdom in their relations to that chronolo The crust of the earth, as we somewhat that portion of its outer shell which is open vation, consists of many beds of rock sup each other, and which must have been dep sively, beginning with the lowest. This is structure of the beds themselves, by the their surfaces, and by the remains of anima which they contain; all these appearances i each successive bed must have been the su was covered by the next. As these beds of rock were mostly formed and of material derived from the waste of not universal, but occur in those places whe extensive areas of water receiving detritus f Further, as the distinction of land and wate rily from the shrinkage of the mass of t from the consequent collapse of the crust i and ridging of it up in others, it follows th from the earliest geological periods, beer |