(_d_) _Asplenieæ._—Here the sorus is elongated or linear. The indusium arises from a vein to which the sorus is attached. Some very charming Ferns belong to this sub-family. Many botanists include the Lady Fern (_Athyrium filix-fæmina_) in this section. Certain of the Spleenworts (_Asplenium_) are common. The Wall Rue (_A. ruta-muraria_) and the Black Maidenhair Spleenwort (_A. adiantum-nigrum_) are well known. (_e_) _Polypodieæ._—The sori on the underside of the leaves are without any indusium. They are in rounded clusters, and look like small buttons. _Polypodium vulgare_ is one of our commonest Ferns. Some of the other species of this genus, such as the Oak Fern (_P. dryopteris_) and the Beech Fern (_P. phegopteris_), are abundant in some localities. (_f_) _Grammitideæ._—The Gold and Silver Ferns. The only British species is the Annual Maidenhair (_Gymnogramma leptophylla_). The plant occurs in the Channel Islands. This species is one of the few Ferns which are not perennial. The sori, which follow the veins, have no indusium. (_g_) _Acrosticheæ._—There are no British representatives of this sub-family. In this case the whole of the underside of the leaf is covered with sporangia, and there is no indusium. 3. _Cyatheaceæ._—There are no British representatives of this family, which is interesting, owing to the fact that it includes the Tree Ferns. 4. _Gleicheniaceæ._—A group of Ferns which are almost entirely tropical. 5. _Schizæaceæ._—Another tropical family. 6. _Marattiaceæ._—A family of large and handsome Ferns, the members of which occur in the tropics. There are not many representatives of this family nowadays, but remains in the Coal Measures show that the species were very much more numerous in Palæozoic times. 7. _Osmundaceæ._—A small family, but rather an important one, owing to the fact that a leading representative, the Royal Fern (_Osmunda regalis_), is so well known. In this species only the upper portion of the leaf is fertile. The sporangia have very short stalks, and are not provided with an annulus at all. They burst open in a longitudinal slit, opposite to a special group of cells just below the apex. The sorus has no indusium. 8. _Ophioglosseæ._—This family is represented by three British species, of which the Moonwort (_Botrychium lunaria_) and the Adder’s Tongue (_Ophioglossum vulgatum_) are best known. There is much doubt as to whether this family can be properly included amongst the Ferns at all. We may here give them the benefit of the doubt. The leaves in these species are unfolded from the sides—a totally distinct plan from that to be observed in all the Ferns which have been described, where the frond and its divisions are unrolled upwards. The prothallus is a small underground body destitute of chlorophyll. The fertile leaves are distinguished from the barren ones by the production of a special branch which bears the fructification. The sporangia are large.