The institution of a special group-name for the reception of _Sphenophyllum_ is justified by the sum of its morphological features, which do not sufficiently conform to those of any existing group of Pteridophytes to warrant its inclusion in a system of classification based on recent genera. In the case of _Cheirostrobus_ we are limited to the characters of the cone and its peduncle. The suggestion that the Devonian fossils known as _Pseudobornia_ may represent the foliage shoots of a plant closely related to _Cheirostrobus_ has still to be proved correct. Although we may find justification in the highly complex and peculiar structure of _Cheirostrobus_ for the recognition of the genus as a type of still another group of Pteridophytes, it would be unwise to take this step without additional knowledge. The undoubted similarity between _Cheirostrobus_ and _Sphenophyllum_ coupled with striking points of difference favours the inclusion of the two genera in distinct families placed, for the present at least, in the group Sphenophyllales. Group =SPHENOPHYLLALES=. =Sphenophylleae=: genus _Sphenophyllum_. =Cheirostrobeae=: genus _Cheirostrobus_. It has recently been proposed to include the family Psilotaceae, comprising the two recent genera _Psilotum_ and _Tmesipteris_, as another subdivision of the Sphenophyllales. This proposal had been made by Professor Thomas[24] primarily on the ground that the sporophylls of _Tmesipteris_ and _Psilotum_ appear to afford the closest parallel among existing plants to the peculiar form of sporophyll characteristic of the Sphenophyllales. The morphological interpretation of the sporophylls of both _Sphenophyllum_ and _Cheirostrobus_ has been the source of considerable discussion[25]. If we regard each sporophyll as a leaf with two lobes, one fertile and one sterile, except in the case of _Sphenophyllostachys fertilis_ in which both are fertile, an obvious comparison may be made with the fern _Ophioglossum_; but the difference between a single fern frond, consisting of a comparatively large sterile lamina bearing a fertile branch composed of a long axis with two rows of sporangia embedded in its tissues, and the whorled sporophylls of _Sphenophyllum_ is considerable. [Sidenote: PSILOTACEAE]