Other abnormalities occur in which the synangium is raised on a distinct stalk instead of being more or less sessile at the point from which the leaf-lobes diverge. A third form of departure from the normal is that in which there is no synangium on the bilobed sporophyll, its place being taken by a leaf-lobe. The deduction from the occurrence of these abnormalities is that the synangium of _Tmesipteris_ represents a ventral leaf-lobe, as Scott suggested. Professor Thomas draws attention to the resemblance between _Tmesipteris_ sporophylls and the foliage-leaves of _Sphenophyllum_, which are either simple with dichotomously branched veins or the lamina is deeply divided into two or more segments. In some types of _Sphenophyllostachys_ the bracts are simple (_S. Dawsoni_), but in others (_Sphenophyllum majus_, fig. 113, C) they are forked like the foliage-leaves and bear a close resemblance to the abnormal sporophylls of _Tmesipteris_. Moreover, in _Sphenophyllostachys Römeri_ (fig. 113, A) each ventral lobe of a sporophyll bears two sporangia, a condition almost identical with that represented by the occasional occurrence of a synangium on a comparatively long stalk in _Tmesipteris_. Similarly the more elaborate sporophylls of _Cheirostrobus_ may be compared with the branched sporophylls of _Tmesipteris_ (fig. 120). This agreement between the sporophylls of the Palaeozoic and recent genera acquires additional importance from the very close resemblance between the exarch stele of _Sphenophyllum_ and that of the genus _Psilotum_, which conforms to the Palaeozoic type not only in the centripetal character of the primary xylem and in its exarch structure, but also in the occasional occurrence of secondary xylem[31], and in the stellate form of its transverse section. The occasional mesarch structure of the stele of _Cheirostrobus_ finds a parallel in the mesarch xylem groups in the stem of _Tmesipteris_. It is thus on the strength of these resemblances that Thomas and Bower would remove the Psilotaceae from the group Lycopodiales and unite them with _Sphenophyllum_ and _Cheirostrobus_ in the Sphenophyllales. While admitting the validity of the comparison briefly referred to above, I prefer to retain the Psilotaceae as a division of the Pteridophyta including only _Psilotum_ and _Tmesipteris_. [Sidenote: SPHENOPHYLLUM]