an inversely orientated cylinder in the central region of the root. This abnormal root does not, however, supply an argument in favour of the derivation of a monostelic type of stem from one that was polystelic, but it shows a close relation between the two plans in one organ. The seedling is not altogether normal in form apart from structure and it is not improbable that the anatomical abnormality is connected with some pathological cause. It has been suggested[423] that Worsdell attaches too much phylogenetic significance to the irregularities in the disposition and form of the vascular bundles in the peduncle of _Stangeria_, and the criticism that insufficient allowance is made for the possible reaction on structure of the special physiological requirements of reproductive shoots is well founded. Granting an overestimate of the arguments drawn from the occasional occurrence of concentric vascular strands, a considerable body of evidence remains in favour of Worsdell’s main contention. Mrs Thoday[424] has drawn attention to certain features exhibited by the inflorescence-axes of _Welwitschia_, particularly the occurrence of concentric and inversely orientated bundles, similar to those characteristic of the seedling of _Cycas siamensis_[425] described by Matte, and to anatomical characters occasionally present in adult cycadean stems and normally represented in _Medullosa_. She is of opinion that the occurrence in _Welwitschia_ of certain Medullosan features has a phylogenetic significance. The differences between the Gnetales, Medulloseae, and Cycadales are considerable, and it would seem unlikely that the anatomical resemblances described by Mrs Thoday are of great value as criteria of close relationship. The comparison of _Lagenostoma_ with gnetalean seeds is alluded to elsewhere. To the statement that the presence of concentric and inversely orientated steles in _Welwitschia_ are reminiscent of the polystelic Medulloseae, Mrs Thoday adds the qualifying remark that the occurrence of four concentric groups of vascular tissue in the hypocotyl of _Welwitschia_ is not sufficient to justify the conclusion that the ancestral type was polystelic. This reservation accords with the contention of Scott and other botanists, that the occasional occurrence in cycadean seedlings and adult stems of anatomical features suggestive of polystely does not in itself furnish an adequate reason for doubting that the apparent monostely of Cycads is phylogenetically what it seems to be, namely, an indication of monostelic ancestry. This brings us to the question of a possible monostelic ancestor. It may be that the Upper Carboniferous genus _Sutcliffia_ affords a clue to the problem of the origin of the polystelic type illustrated in various forms by _Medullosa_. The protostele of _Sutcliffia_ bears a close resemblance to each of the three steles of _Medullosa anglica_; the fact that _Sutcliffia_ is exarch and that _Medullosa anglica_ has mesarch xylem