Seeing that the number of true ferns of Palaeozoic age has been recently considerably reduced and is likely to suffer further reduction, the consideration of such undoubted Carboniferous and Permian examples of the Filicales as are left acquires a special importance. In the first place it is natural to ask whether the Palaeozoic ferns include any types which, if not themselves ancestral forms, may serve to indicate the probable lines of evolution of existing families. It is probable that in the near future our knowledge of the Coenopterideae will be considerably extended; as yet we possess meagre information in regard to those characters on which most stress has generally been laid in the classification of recent ferns, namely the structure of the spore-bearing organs. The sporangia of _Diplolabis_ and _Stauropteris_ (figs. 309, A; 322) are exannulate; in the former genus they occur in sori or synangia consisting of a small number of sporangia, while in the latter they are borne singly at the tips of ultimate ramifications of a highly compound leaf. The resemblance of the synangium of _Diplolabis_ to that of _Kaulfussia_ (fig. 245, C) is not shared in an equal degree by the sporangia of _Stauropteris_, which are in some respects comparable with those of the Ophioglossaceae. In the Zygoptereae, or at least in the case of such fertile fronds as are known, and in _Botryopteris_ (fig. 319), the sporangia occur in groups, and the pedicel of each sporangium is supplied with vascular tissue as in _Helminthostachys_. Another characteristic of the sporangia of the extinct types is the possession of an annulus several cells in breadth, a peculiarity which supplies a point of contact with the Osmundaceae. In the sporangia of _Kidstonia_ we have a similar though not an identical type (fig. 256, E, p. 340). So far, then, as the evidence afforded by sporangial characters is concerned, it points to comparison with the Ophioglossaceae, the Osmundaceae, and the Marattiaceae. When we compare the steles of the stems we find a wide range of structure. All the genera agree in being monostelic; in _Tubicaulis_ and _Grammatopteris_ the protoxylem is exarch, in _Botryopteris_ it is internal, while the foliar strand of _Stauropteris_ and the stele of _Ankyropteris corrugata_ are mesarch. The axillary branching of species of _Ankyropteris_ suggests comparison with the Hymenophyllaceae. The investigation of the vascular system of the petioles has afforded results which in the hands of P. Bertrand have led to conclusions in regard to inter-relationships. We must, however, not overlook the danger of attributing can excessive importance to this single criterion and of neglecting the facts of stem anatomy. I. Botryoptereae. _Grammatopteris._