This species, originally described by Corda as Pecopteris Zippei[864] and afterwards figured by Heer[865] as Gleichenia Zippei ([fig. 262], D) from Urgonian rocks of Greenland, affords a striking example of a Mesozoic member of the Gleicheniaceae. It is characterised by the dichotomous branching of the frond and by the occurrence of arrested buds in the forks. The long and slender pinnae, reaching a length of 9 cm. and a breadth of 6–8 mm., bear small crowded pinnules occasionally with circular sori which are described by Heer as consisting of a small number of sporangia (cf. [fig. 262], C). Several other Lower Cretaceous species are recorded by Heer from Greenland, some of which are probably unnecessarily separated from Gleichenites Zippei. Examples of these are represented in [fig. 262], A, B, C.
A Gleicheniaceous species described by Debey and Ettingshausen from Lower Cretaceous rocks of Aix-la-Chapelle as Didymosorus comptonifolius[866] is very similar in habit to some of Heer’s Greenland species: this should probably be referred to the genus Gleichenites.
Gleichenites hantonensis, Wank. Fig. 263.
From the Eocene beds of Bournemouth, Gardner and Ettingshausen[867] have described under the name Gleichenia hantonensis what is in all probability a true Gleichenia ([fig. 263]). This species, originally recorded by Wanklyn[868], is characterised by a slender forked rachis showing what may be traces of arrested buds between the arms of the branches, by circular sori of six or eight sporangia and by the presence of peculiar tendril-like appendages on the pinnae. If the description of the tendrils is correct, this British species affords one of the few instances of ferns adapted for climbing and may be compared with the recent species Davallia aculeata ([fig. 232], p. 299).
Matonineae.
The genera Laccopteris and Matonidium may be described as examples of Mesozoic ferns exhibiting a very close agreement with Matonia.
Laccopteris. This genus, founded by Presl[869], may be described as follows:—
Frond pedate, in habit resembling Matonia pectinata, with pinnate or pinnatifid pinnae; ultimate segments linear, provided with a well-marked midrib giving off numerous dichotomously branched secondary veins which are in places connected by lateral anastomoses. Sori circular, forming a single row on each side of the midrib ([fig. 278], B); sporangia 5–15 in each sorus, with an oblique annulus and tetrahedral spores. The presence of an indusium is not certainly established.
Fig. 263. Gleichenites hantonensis Wank. (Restoration, after Gardner and Ettingshausen.)