The first includes the Marattiaceae, Osmundaceae, Schizaeaceae, Gleicheniaceae and Matoniaceae; the second the Loxsomaceae, Hymenophyllaceae, Cyatheaceae and the Dennstaedtineae (a group including species placed in the Synopsis Filicum in Dicksonia and Davallia); while the remaining Polypodiaceae constitute the Mixtae.
The Gleicheniaceae appear to have been represented by Triassic species in North America and Europe, and more abundantly in Jurassic, Weal den, or Lower Cretaceous rocks 3 4 in Belgium, Greenland, Poland s and elsewhere.
Certain fructifications have been referred to Gleicheniaceae (Oligocarpia, fig.
Part of the Mesozoic period the Gleicheniaceae held a position in the vegetation of the far north similar to that which they now occupy in the southern tropics of India and other regions.
When the survey is extended to the extinct Ferns of which the fructification is known, many of those from the more ancient rocks are found to group themselves with the existing sub-orders with large sporangia, such as the Marattiaceae, Gleicheniaceae and Schizaeaceae; the Polypodiaceae, on the other hand, do not appear until much later.