The question of the relationship between different families of recent ferns and the older known fossil members of the group is beyond the scope of this book. Evidence has been discovered in recent years which warrants the statement that, although none of those Carboniferous ferns were generically identical with existing forms, they very clearly foreshadowed some of those structural features which characterise more than one family of present-day Ferns. The records of the older Mesozoic formations afford abundant evidence of the existence of certain types of Ferns showing a very close resemblance to recent species. [Illustration: Fig. 9. _Osmunda regalis_ Linn. Fertile frond, (2/5 nat. size.)] An enquiry into the geographical distribution of living Ferns reveals facts of special interest in connexion with the relative antiquity of different genera and families. The wide distribution of the Bracken fern has already been referred to: it is abundant in Tasmania; its vigour in the island is well illustrated by Mr Geoffrey Smith's statement that constant attention is necessary to keep it from invading newly opened country(45). On Mount Ophir in the Malay Peninsula the cosmopolitan bracken occurs in association with the two genera Matonia and Dipteris, ferns which are among the most striking examples of links with a remote past and have a restricted geographical range. With _Osmunda regalis_, the Royal Fern, the Bracken is conspicuous in the marsh vegetation of the Bermudas; it flourishes on the Atlas Mountains, in the Canary Islands, in Abyssinia, on Mt Kenia, in British East Africa, in the Himalayas, and is in fact generally distributed in the tropics in both the north and south temperate zones. The Royal Fern (Fig. 9) is another British species with a wide distribution; it occurs in Northern Asia and in North America; it is common in the Siberian forests and lives in several tropical countries, extending to Southern India and Cape Colony, and in South America it is represented by a closely allied species. Though at the present day _Osmunda regalis_ is one of the rare English Ferns, its occurrence in the submerged forest-beds round our coasts and in pre-Glacial beds points to its former abundance in the British area generally. The Royal Fern is a member of a family now represented by two genera, Osmunda and Todea. With the exception of _Todea barbara_, with its large spreading fronds and a short root-covered stem, which occurs in Australia and Cape Colony, all the species of this genus are filmy ferns with semitransparent fronds adapted to a moisture-laden atmosphere. The maximum development of the genus is in New Zealand. _Todea barbara_ affords an instance of discontinuous distribution; it was no doubt once widely spread in circumpolar regions and now survives only in South Africa and in Australia.