The primitive Osmundaceous stele was composed of solid xylem surrounded by phloem (_Thamnopteris_ and _Zalesskya_); at a later stage the xylem cylinder lost its inner zone of wide and short tracheae and assumed the form seen in _Osmundites Kolbei_, in which the centre of the stele consists of parenchyma with some tracheae. Another type is represented by _O. Dowkeri_ in which the pith is composed wholly of parenchyma and the xylem ring is continuous. From this type, by expansion of the xylem ring and by the formation of overlapping leaf-gaps, the form represented by _Osmunda regalis_ was reached. _Osmunda cinnamomea_, with internal phloem in the regions of stelar branching, probably represents a further stage, as Kidston and Gwynne-Vaughan believe, in increasing complexity due to the introduction of phloem from without through gaps produced by the branching of the stele. In _Osmundites skidegatensis_ the leaf-gaps became wider and the external phloem projected deeper into the stele until a continuous internal phloem zone was produced. This most elaborate type proved less successful than the simpler forms which still survive. _Osmundites Sturii._ Impressions of fertile pinnae with narrow linear segments bearing exannulate sporangia described by Raciborski from Lower Jurassic rocks in Poland as _Osmunda Sturii_[794] may with some hesitation be included in the list of Mesozoic Osmundaceae. _Osmundites Dowkeri._ Under this name Carruthers[795] described a petrified stem from Lower Eocene beds at Herne Bay, which in the structure of the stele agrees closely with the Jurassic species _O. Gibbiana_ and conforms to the normal Osmundaceous type. It is possible, as Gardner and Ettingshausen[796] suggested, that the foliage of this species may be represented by some sterile _Osmunda_-like fragments recorded from the Middle Bagshot beds of Bovey Tracey and Bournemouth as _Osmunda lignitum_. _Todites._ This generic name[797] has been applied to fossil ferns exhibiting in the structure of the sporangia and in the general habit of the fertile fronds a close resemblance to the recent species _Todea barbara_ (fig. 221, D, p. 286). _Todites Williamsoni_ (Brongniart) figs. 256, B, C, G. 1828. _Pecopteris Williamsonis_, Brongniart, Prodrome, p. 57; Hist. vég. foss., p. 324, Pl. CX. figs. 1 and 2. —— _P. whitbiensis_, Brongniart, Hist. vég. foss. p. 321, Pl. CIX. figs. 2–4. —— _P. tenuis_, _ibid._ p. 322, Pl. CX. figs. 3, 4. 1829. _Pecopteris recentior_, Phillips, Geol. Yorks. p. 148, Pl. VIII. fig. 15. —— _P. curtata_, _ibid_. Pl. VIII. fig. 12. 1833. _Neuropteris recentior_, Lindley and Hutton, Foss. Flora, Vol. I. Pl. LXVIII. —— _Pecopteris dentata_, _ibid._ Vol. III., Pl. CLXIX. 1836. _Acrostichites Williamsonis_, Goeppert, foss. Farn. p. 285. 1841. _Neuropteris Goeppertiana_, Muenster, in Goeppert, Gattungen foss. Pflanz. Lief. 5 and 6, p. 104, Pls. VIII.–X.