Fossil plants, Vol. 2 : $b A text-book for students of botany and geologySeward, A. C. (Albert Charles)
Science
Fossil plants, Vol. 2 : $b A text-book for students of botany and geology
Seward, A. C. (Albert Charles)
Paleobotany
This species is represented in several Wealden localities by fragments
of fertile pinnae similar to those of _L. polypodioides_. It is almost
impossible to distinguish small specimens of the Wealden fern from
Heer’s genus _Nathorstia_ (Marattiaceae) unless the sori are well
preserved. This species occurs in Wealden beds in England, Germany,
Belgium, and elsewhere and has been discovered by Dr Marcus Gunn in
Upper Jurassic plant-beds of Sutherlandshire (N.E. Scotland).
• • • • •
_Laccopteris_ is widely spread in Rhaetic, Jurassic and Lower
Cretaceous floras. It affords evidence of the former abundance in
northern latitudes of a family now represented by the two species of
_Matonia_ confined to a restricted area in the southern hemisphere.
_Matonidium._
Schenk[879] instituted this convenient term for fossil fern fronds
agreeing in habit and in their sori with _Matonia pectinata_ (figs.
227, 228, p. 292). Zeiller[880] has drawn attention to the fact
that the Mesozoic species differ from the surviving types in the
greater number of sporangia in each sorus, and, it may be added,
in _Matonidium_ the fertile pinnules are more richly supplied with
sori than are those of _Matonia_. Unfortunately our knowledge of the
structure of the sporangia of _Matonidium_ is less complete than in the
case of _Laccopteris_, but such evidence as is available justifies the
conclusion that _Matonia_ is a direct descendant of ferns which formed
a prominent feature in European Jurassic and Wealden floras. It is
interesting to find that in a Cretaceous species, described by Krasser
(fig. 265, A) since the publication of Zeiller’s paper, the sori appear
to be identical in distribution and in appearance with those of the
recent species.
I am indebted to Prof. Bommer for permission to reproduce the
unpublished drawing represented in fig. 237 D (p. 310) of a section of
the rhizome of _Matonidium_ from the Belgian Wealden beds of Hainaut
(“Flore Bernissartienne”). The section shows an arrangement of vascular
tissue identical with that in the recent species: there may be two
solenosteles and in addition a solid axial strand. The form of the
leaf-trace in the fossil appears to be identical with that in _Matonia
pectinata_ (fig. 237, A, p. 310).
_Matonidium Goepperti_ (Ettingshausen)[881]. Fig. 269.
Under this name are included specimens from Inferior Oolite and Wealden
strata in Britain and elsewhere. It is, however, not impossible that if
more information were available, we should find adequate reasons for
recognising two specific types. Fontaine[882], adhering rigidly to the
rules of priority, speaks of this species as _Matonidium Althausii_
(Dunker), but Ettingshausen’s specific term is better known.
[Illustration: FIG. 269. _Matonidium Goepperti_ (Ettings.). (A, B, ½
nat. size; C, approximately nat. size.)]
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