The Upper Triassic ferns described by Heer, Krasser[1045], and Leuthardt[1046] as Bernouillia have been referred to the Marattiaceae, but without trustworthy evidence in favour of this affinity.

The large leaves, 70 cm. long and 7 cm. broad, described by Zigno[1047] from the Jurassic of Italy as Danaeites Heeri, are probably Cycadean. The Polish Jurassic species Danaea microphylla[1048] is a more satisfactory record.

Fig. 294.

Nathorstia.

This name was instituted by Heer[1049] for pieces of pinnate fronds from Lower Cretaceous rocks of Greenland. The resemblance of the long pinnules to the fertile segments of Laccopteris is so close that generic identity might well be assumed, but it has recently been shown by Nathorst[1050] that the soral characters justify Heer’s use of a distinctive name for the Arctic fern. The circular sori arranged in two rows ([fig. 294], A, B) are superficially identical with those of Laccopteris, but consist of concrescent sporangia forming a circular synangium ([fig. 294], C, D) like those of Kaulfussia and Ptychocarpus. The lighter areas in [fig. 294], D, represent the sporangia: fig. C shows the radial disposition of the numerous sporangial compartments round a central receptacle. From a stout midrib lateral veins arise at right angles, but their distal terminations are not preserved. It is probable, as Nathorst suggests, that Bayer’s[1051] species Drynaria fascia from the Lower Cretaceous rocks of Bohemia should be referred to Heer’s genus. In the absence of well-preserved sori it would be exceedingly difficult, or even impossible, to distinguish between pinnules of Laccopteris and Nathorstia.

A Tertiary species, Marattia Hookeri ([fig. 261], C, p. 350), described by Gardner and Ettingshausen[1052] from the Eocene beds of the Isle of Wight is referred by them to the Marattiaceae because of a resemblance of the sterile pinnae to those of M. Kaulfussii; but this is insufficient evidence of relationship.

CHAPTER XXIII.