An interesting feature in the stems is the occurrence of cortical vascular strands (fig. 416, A, _a_, _b_), reaching a diameter of 7 mm., containing scattered tracheids in a parenchymatous core surrounded by secondary xylem and phloem. These cauline bundles are almost identical both in structure and distribution with the accessory steles in the stem of a recent _Cycas_, and the agreement is emphasised by the presence of short square-ended tracheids in the primary xylem. The roots branch freely and may attain a diameter of more than 1 cm.: they are generally triarch and the triangular primary xylem is enclosed by secondary xylem except opposite the protoxylem. The cortex is like that of _Lyginopteris_ roots and a conspicuous double layer of superficial tissue is another feature common to both (_cf._ fig. 410). The exceptionally well preserved specimens described by Arber[248] show very clearly the thick zone of periderm which forms the covering of older roots, and in some of the sieve-tubes groups of dark brown patches show the form and arrangement of the sieve-plates. _Reproductive organs._ We have as yet no precise information in regard to the reproductive organs of _Medullosa anglica_, but there can be little or no doubt that the fronds bore seeds that have long been known under the generic name of _Trigonocarpus_. Many years ago Mr Hemingway noticed the almost constant association of the fronds of _Alethopteris lonchitica_ with _Trigonocarpus_, and Dr Kidston’s discovery[249] of seed-bearing _Neuropteris_ pinnae considerably strengthened the evidence derived from mere association. The structure of _Trigonocarpus_ is described later (p. 117) in a section devoted to reproductive organs attributed to _Medullosa_. Nothing is known as to the microspore-bearing organs. While in the structure of each of the steles _Medullosa anglica_ agrees very closely with _Heterangium_, it differs from that genus in the presence of three steles and in the structure of the petioles which are much less fern-like than the simpler petioles of _Heterangium_ and _Lyginopteris_. From the continental species the British species is distinguished by its simpler stelar system, though there is a close correspondence as regards individual steles. _Medullosa pusilla_ Scott.