44 



BRITISH EOCENE ELOEA. 



racid teiiui ; pinnis ohhngis ; pimiidis appro ximatis patentibus, linearihus vel lanceolato- 

 ohlongis, margine integerrimis vel crenatis ; apice oMusis ; nervatione Pecopteridis verce ; 

 nervo prhiiario e racld angulo subacuto, rarius recto exeunte, tenui, plus minusve Jlexuoso ; 

 nervis secundarm cum primario angulos acutos formantibus, abbreviatis, catadro7rds,furcatis, 

 rarius simplidbus ; nervis tertiariis catadromis, arcuatis, simplicibus, rarius furcatis, 

 injimo lateris exterioris receptaculum pnnctiforme emittente. Soris singularibus vel duobns 

 rotundis, lobatis. 



Middle Bagshot, Bournemouth. 



The stipes and rachis are slender, and are always found associated with the remains of, 

 and sometimes attached to the pinnules The repeatedly dichotomosing character of the 

 stem is well seen in the specimen, PI. VI, fig. 8, in which is also shown one of the young 

 buds produced at the forking of the larger stipes. The stipitss were furnished with short, 

 hook-like tendrils. Eigs. 9 and 10 show these tendrils with remains of the rachis, and 

 fig. 11 with the attachment to the stipes only. On this piece and at fig. 8 are spirally 

 rolled buds. The relative position of the tendrils and pinnae is shown on PI. X, fig. 2. 

 The remains of pinnae, represented in PI. VI, figs. 1, 2, 3, and 7, show them to have 

 been of an elongated, almost lanceolate shape, bearing linear or lanceolate pinnules of 

 unequal length. These are closely set, with crenate or entire margin and rounded apex. 

 The venation is that of Pecopteris vera. The midribs of the pinnules are sinuous and 

 relatively slender; they leave the rachis, which is itself slightly flexuous, at angles of 65° 

 to 80°, rarely either more acute or obtuse. The secondary veins leave the midrib in cata- 

 dromous order at the same angles as those formed by pinna and rachis, and are mostly 

 forked, rarely simple. The ternary veins are also catadromous and mostly simple. The 

 sori occur on one or both of the exterior venules of each group of veins. The sporangia 

 were deciduous, and arranged round a small, oval, punctiform receptacle. There are 

 visible six to eight impressions to each cluster, but only the bases of these are seen in 

 places where the leaf has chipped off. 



The fossil form is distinguished from all existing Gleichenia by the possession of 

 tendrils or hooks, indicating a more pronounced creeping or climbing habit. With this 

 exception, however, it bears a close resemblance to two recent species, forming sections 

 of the sub-genus Mertensia, G. pecti7iafa and G. dichotoma. The size and form of the 

 pinnae, the branched and zigzag stipes, the buds occurring in the forks, the venation, 

 and the sori, are all similar. The resemblance is considerably heightened by the very 

 unequal lengths of the pinnules, even when side by side, and by the fact that only those 

 which are much longer than the rest are regularly crenated, as if the crenations were an 

 expression of luxuriant growth. Adiantoid bracts are sometimes developed at the 

 forkings, and these, being found associated with the fossil Gleichenia, had been thought 

 to indicate the presence of Adiantum. 



G. pectinata, which it the more particularly resembles, is a native of tropical South 



