In his account of _Lepidodendron mundum_, Williamson[644] described a section in which the primary wood is surrounded by a considerable thickness of secondary xylem; a diagram of this is shown in fig. 215, C. An examination of the section led me to compare the structure of the outer cortical cells, characterised by radial rows of tangentially elongated elements, with the outer cortex of _Stigmaria_. It has recently been shown by Weiss[645] that this and other similar sections present several points of agreement with _Stigmaria_, particularly with _Stigmaria Brardi_ as described by Renault. At _s_ in fig. 215, C, a vascular strand is seen passing through the outer cortex; this is almost certainly the bundle of a rootlet: in the sections described by Weiss rootlets are shown in a similar position. The chief anatomical features of the Stigmaria-like organs of _Bothrodendron_ are:—the considerable development of secondary xylem, the structure of the outer cortex, which is practically identical with that of _Stigmaria ficoides_, and the association of groups of short transfusion tracheids with the bundles of the rootlets. It is very probable that the absence of secondary xylem in the vegetative shoots of _Bothrodendron_ is merely an accident and not a real distinction between the aerial and subterranean branches of the plant; a supposition rendered probable by the occurrence of secondary xylem in the axis of the cone described by Watson. As Weiss points out, there are certain differences between the true _Stigmaria_ and the corresponding organ of _Bothrodendron_; the secondary xylem in _Bothrodendron_ is not broken up by broad medullary rays as in the common _Stigmaria_, and in _Bothrodendron_ the occurrence of a ring of primary xylem is another peculiarity. In the vegetative shoots of _Bothrodendron mundum_ the stele differs from those of _Lepidodendron_ in the narrower primary xylem ring and in the large size of the metaxylem tracheae; from _Lepidodendron Harcourtii_ and _L. fuliginosum_ the xylem is distinguished by its smoother outer face which consists of numerous narrow xylem elements. [Illustration: FIG. 216. _Bothrostrobus._ _l_, ligule. (After Watson.)] _Cones_ of Bothrodendron (_Bothrostrobus_[646]).