•••••

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.
1856.Pecopteris Huttoniana, Zigno, Flor. foss. Oolit. Vol. I. p. 133.
1867.Acrostichites Goeppertianus, Schenk, Foss. Flor. Grenzsch. p. 44, Pl. V. fig. 5, Pl. VII. fig. 2.
1883.A. linnaeaefolius, Fontaine, Older Mesoz. Flora Virginia, p. 25, Pls. VI.–IX.
—A. rhombifolius, ibid. Pls. VIII. XI.–XIV.
1885.Todea Williamsonis, Schenk, Palaeont. Vol. XXXI. p. 168, Pl. III. fig. 3.
1889.Cladophlebis virginiensis, Fontaine, Potomac Flora, p. 70, Pl. III. figs. 3–8; Pl. IV. figs. 1, 4.