Ophioglossales (Fossil).
The fossils hitherto classed with the Ophioglossales are not such as
afford any satisfactory evidence in regard to the past history or
phylogeny of the group. In the generalised class of Palaeozoic ferns,
the Botryopterideae, we find certain characters suggesting comparison
with recent members of the Ophioglossaceae, but no trustworthy records
of these eusporangiate ferns are furnished by the older plant-bearing
strata.
[Illustration: FIG. 301. _Rhacopteris_ sp., Ballycastle, Ireland. From
a specimen in the Manchester Museum. [M.S.]]
The genus _Rhacopteris_ (fig. 301), characteristic of the Culm flora,
has been compared with _Botrychium_, but on grounds which are wholly
inadequate. The species _R. paniculifera_ Stur[1095] is characterised
by a stout rachis bearing two rows of laterally attached rhomboidal
or subtriangular segments with a more or less deeply lobed margin
and spreading veins. The rachis branches distally into two arms, and
these are again symmetrically subdivided into fertile axes bearing
clusters of small spherical bodies 1 mm. broad, which Stur speaks of as
exannulate sporangia similar to those of _Botrychium_. He includes the
species in the Ophioglossaceae. As Zeiller[1096] pertinently remarks,
_Rhacopteris_ differs essentially in habit from any recent member of
this family. _Rhacopteris_ also includes species characterised by
leaflets deeply dissected into linear segments; an example of this
form is represented by _Rhacopteris flabellata_ (Tate) recorded by
Kidston[1097] from rocks of Calciferous Sandstone age in Flintshire.
The specimen described by Renault[1098] from the Carboniferous rocks
of Autun as _Ophioglossites antiqua_ is equally unconvincing: it
consists of a carbonised fragment, 7 cm. × 1·5 cm., regarded as part
of a fertile lamina characterised by a vertical series of transversely
elongated slits, 7 mm. wide, some of which, on slight magnification,
are seen to contain a mass of small orange-yellow granulations.
The slits are compared with the surface-openings of the sunken
sporangia of _Ophioglossum_, and the yellow bodies are identified as
spores. The material is too imperfect to justify the use of the name
_Ophioglossites_.
_Noeggerathia._
This genus of uncertain position may be briefly described here,
though it has little claim to recognition as a representative of the
_Ophioglossales_. It is characteristic of Lower Carboniferous rocks and
is compared by Stur[1099] with recent Ophioglossaceae. _Noeggerathia
foliosa_ Sternb. (fig. 302) may be cited as a typical example of the
genus. It consists of an axis bearing ovate leaves with numerous
spreading veins. The upper part of the axis forms a spike composed of
fertile leaves in the form of transversely oval bracts 2 cm. broad with
a serrate edge bearing on the upper face several sporangia (3 × 4 mm.)
in some of which spores have been seen (fig. 302, B, C). In another
form described by Weiss[1100] the bracts bear a greater number of
sporangia characterised by the presence of an arillus-like basal ring.
[Illustration: FIG. 302. _Noeggerathia foliosa._ (After Stur; A,
reduced.) B, Fertile leaf; C, Sporangium.]
Geinitz[1101], who first described fertile specimens of _Noeggerathia_,
placed the genus in the Gymnosperms, and O. Feistmantel[1102] was in
favour of this view. C. Feistmantel[1103], who described the small
bodies in the sporangia, suggested comparison with Schizaeaceae, and
Weiss[1104] discussed various possibilities, asking but not answering
the question, are the so-called sporangia rightly so named or are
they fruits? Potonié[1105] places the genus in the Cycadofilices. An
important feature is the occurrence of the sporangia on the upper face
of the bracts as in Lycopodiales and _Sphenophyllum_, but in other
respects _Noeggerathia_ bears no resemblance to these two groups.
Sterile examples of the genus are similar in habit to _Rhacopteris_,
but in the latter genus the leaves or leaflets are laterally
attached and not obliquely inserted. Further, we may assume that in
_Rhacopteris_ the segments are leaflets of a compound leaf, whereas
in _Noeggerathia_ they are probably single leaves. We must leave the
position of this Lower Carboniferous genus undecided, merely expressing
the opinion that it is perhaps more nearly allied to the Cycads than to
any other group.
[Illustration: FIG. 303. _Chiropteris Zeilleri_, Sew. [From a specimen
in the British Museum (v. 3268). Nat. size.]]
The plant figured by Lindley and Hutton from the English Coal-Measures
as _Noeggerathia flabellata_, which some authors quote as a species of
_Noeggerathia_, is generally recognised as a _Psygmophyllum_ and placed
with some hesitation in the Ginkgoales.
_Chiropteris._
This genus was founded by Kurr on a leaf characterised by anastomosing
venation from Keuper beds near Stuttgart. A resemblance in form and
venation to the leaves of recent species of _Ophioglossum_ led authors
to suggest the inclusion of Kurr’s specimen in the Ophioglossaceae.
We have, however, no justification for considering _Chiropteris_ as a
member of this family; it may be a fern, and that is all that can be
said. The leaf represented in fig. 303 is the type-specimen of a South
African Rhaetic species _Chiropteris Zeilleri_[1106]. The genus is
recorded also from Rhaetic rocks in Queensland.[1107]
Newberry[1108] describes some leaves from the Lower Cretaceous of
Montana as species of _Chiropteris_: one of his types, _C. spatulata_,
is almost certainly a _Sagenopteris_, similar to _S. Phillipsi_ (figs.
327, 328) or _S. Mantelli_. A second species, _C. Williamsii_, is
probably not generically identical with the specimen represented in
fig. 303.