ii. _Leaves._ Before describing a second type of stem referred to _Cladoxylon_ it is important to consider briefly such evidence as we have as to the vascular supply of the leaves. Nothing is known of the reproductive organs and there is no satisfactory information with regard to the form of the fronds. Solms-Laubach has described the only known example of a lateral branch of a _Cladoxylon_ stem (fig. 459, E): this has a single concentric vascular strand of plate-like form with two blunt projections and there are four protoxylem-groups, two in the angle of the plate and two at the base of the projections. The structure is essentially fern-like; the xylem is wholly primary. This type of vascular strand agrees fairly closely with that of a petiole described by Unger as _Megalorhachis elliptica_, a section of which is in the Museum of the Geological Survey[518]. The petiole is oval in section and laterally winged, and the meristele is tangentially elongated and has two blunt projections almost identical with those in fig. 459, F. There is no evidence as to the nature of the supporting stem, but there can be little doubt as to the close connexion with _Megalorhachis_ and the section shown in fig. 459, F. In a note published in 1908 P. Bertrand stated that he had identified several of Unger’s genera as stems which bore leaf-traces having the form and structure of _Clepsydropsis_, one of the types referred by Unger to the Rhachiopterideae and described in the second volume of this work[519] as a Coenopteridean petiole. Bertrand points out that in the oval or plate-like steles of _Cladoxylon_, _Arctopodium_, _Hierogramma_, etc., there is a single protoxylem group near the distal end of the primary xylem, and he adds that the leaf-traces were formed of strands cut off from the distal portions of the vascular plates. Similarly the hour-glass-like leaf-trace in the primary rachis of _Clepsydropsis_ gives off from each end a ring of xylem to supply a secondary rachis. These laterally detached annular strands are, he believes, similar to the leaf-trace cut off from the steles in a _Cladoxylon_ stem. The conclusion is that _Cladoxylon_ is a fern stem and its leaf-trace represents the simplest form of the _Clepsydropsis_ type, namely an oval bundle of xylem with a central protoxylem, which is also the form of the trace given off from the stem of _Asterochlaena_. Solms[520], while admitting that Bertrand may be correct in uniting under one genus _Cladoxylon_ and such types as _Syncardia_, _Hierogramma_, and _Arctopodium_, disagrees with the view that they are _Clepsydropsis_ stems. A Clepsydropsoid leaf-trace has never been found in direct association with any of the stems of the _Cladoxylon_ type and such evidence as there is indicates a leaf-trace of an entirely different form (fig. 459, E). In his more recent memoir on _Asterochlaena_ Bertrand[521] draws attention to Solms’ figures of a stele of _Cladoxylon_ (fig.