There are, of course, exceptions, and, as will be noted later on (see Chapter XVII), there are fossil seaweeds and fossil freshwater plants, but we may take it on the whole that the fossils we shall have to deal with and that give important evidence, are those of the land which had drifted out to sea, in the many cases when they are found in rocks together with sea shells. Let us now consider very shortly the salient features of the seven epochs we have named as the chief divisions of time. The vegetation of the Carboniferous Period is better known to us than that of any other period except that of the present day, so that it will form the best starting-point for our consideration. At this period there were, as there are to-day, oceans and continents, high lands, low lands, rivers and lakes, in fact, all the physical features of the present-day world, but they were all in different places from those of to-day. If we confine our attention to Britain, we find that at that period the far north, Scotland, Wales, and Charnwood were higher land, but the bulk of the southern area was covered by flat swamps or shallow inlets, where the land level gradually changed, slowly sinking in one place and slowly rising in others, which later began also to sink. Growing on this area wherever they could get a foothold were many plants, all different from any now living. Among them none bore flowers. A few families bore seeds in a peculiar way, differing widely from most seed-bearing plants of to-day. The most prevalent type of tree was that of which a stump is represented in the frontispiece, and of which there were many different species. These plants, though in size and some other ways similar to the great trees of to-day, were fundamentally different from them, and belonged to a very primitive family, of which but few and small representatives now exist, namely the Lycopods. Many other great trees were like hugely magnified “horsetails” or Equisetums; and there were also seed-bearing Gymnosperms of a type now extinct. There were ferns of many kinds, of which the principal ones belong to quite extinct families, as well as several other plants which have no parallel among living ones. Hence one may judge that the vegetation was rich and various, and that, as there were tall trees with seeds, the plants were already very highly evolved. Indeed, except for the highest group of all, the flowering plants, practically all the main groups now known were represented. The flora of the Devonian was very similar in essentials.