A plant originally described by Williamson[1125] from the Lower Coal-Measures of England as _Rachiopteris cylindrica_ (fig. 305) and afterwards more fully dealt with by Hick[1126], has a slender stem with a cylindrical stele characterised by well-defined central protoxylem elements in one or two groups. The leaf-traces are semi-lunar in section with the protoxylem on the flatter side. The stele of _Botryopteris cylindrica_ (fig. 305, A) is more cylindrical in section than that of _B. ramosa_ (fig. 306) and shows more clearly the differentiation into smaller central and larger peripheral tracheae. In the section reproduced in fig. 305, B the stele is giving off a branch almost identical in structure with the main vascular axis. Scott[1127], in referring to the inclusion of this type in the genus _Botryopteris_, expresses the opinion that its habit must have been very different from that of other species, and he suggests the institution of a new genus. [Illustration: FIG. 305. _Botryopteris cylindrica_ (× 30). From sections in the Cambridge Botany School.] _Botryopteris ramosa_ (Williamson). Fig. 306. This species, which bears a close resemblance to _Botryopteris hirsuta_, was originally described by Williamson from the Lower Coal-Measures of England as _Rachiopteris ramosa_[1128], the specific name being chosen on account of the numerous and crowded branches given off from the main axis. The section shown in fig. 306, A, illustrates Williamson’s description of the stem as being “always surrounded [when seen in transverse sections] by a swarm of similar sections of the large and small branches, though of varying shapes and sizes.” The stele is composed of a solid and more or less cylindrical rod of xylem tracheae of the reticulate type surrounded by phloem (figs. A and D): one or more internal groups of smaller protoxylem elements occur in an approximately central position (fig. A, _px_). The stele is in fact endarch like those of _Selaginella spinosa_ and _Trichomanes reniforme_, a feature which, as Tansley[1129] believes, probably entitles the vascular axis to be considered a primitive form of protostele. In the specimens represented in fig. 306 the phloem and inner cortical tissues were almost completely destroyed before petrifaction. The thick-walled outer cortex bears at its periphery numerous multicellular hairs. Some of the xylem strands given off from the stele no doubt supplied adventitious roots, but in most cases the outgoing branches are leaf-traces and the numerous sections of axes of different sizes seen in fig. A point to a repeated subdivision of the crowded fronds. The structure of a petiole is shown in figs. C and D. As seen in fig. C, the oval vascular strand has three protoxylem groups, _px_, on its flatter side; a well-defined epidermal layer is shown at _e_ in fig. C.