Chapter XXVII (2)

The term _Aphlebia_ may be applied also to the Cyclopteroid pinnules on the petioles of some species of _Neuropteris_, _Odontopteris_ and _Archaeopteris_. Goebel[1399] has referred to the application by Potonié and other authors of the term Aphlebioid to the pinnules which serve as bud-protecting organs in recent fronds of _Gleichenia_ (fig. 226, p. 290); he expresses the opinion that it is superfluous and misleading to make use of a special designation for structures which are undoubtedly modified pinnules. In the case of fossils it is, however, convenient to employ the term _Aphlebia_ as a descriptive name for modified pinnules or stipular structures which cannot be connected with definite species of fronds. It is clear that some Aphlebiod leaflets, such as those of _Dactylotheca_, served as protective organs for the unexpanded pinnae[1400], and in all probability the large Aphlebiae served the same purpose as the fleshy stipules of _Angiopteris_ and _Marattia_ which cover the uncoiled fronds. The pinnatifid scale-leaves of considerable size (fig. 351) which occur in the leaf-axils or as ochrea-like stipules on the fronds of _Gunnera_ (a tropical and subtropical Dicotyledonous genus) bear a very close resemblance to some Palaeozoic Aphlebiae, e.g. _Aphlebia crispa_ (Gutb.). The recent and fossil scale-leaves may be regarded as similar in function as in form; moreover the delicate coiled fronds of Palaeozoic Pteridosperms or ferns, like those of some recent flowering plants, may have been kept moist by a secretion of mucilage. The pinnatifid stipules of _Marattia fraxinea_ (fig. 241, B, p. 317) resemble certain fossil Aphlebiae, and the wrinkled surface of the recent stipules presents an appearance similar to that which in some fossil forms has been erroneously described as veining. It is not improbable that mantle-leaves of such recent ferns as _Polypodium quercifolium_ (fig. 234, M, p. 303) are comparable with some fossil Aphlebiae which may have served as humus-collectors for Palaeozoic epiphytes.

The filiform appendages on the petioles of the recent fern _Hemitelia capensis_ (fig. 235, p. 304) have often been compared with the aphlebioid leaflets of fossil fronds.

Potonié who has discussed the nature of Aphlebiae regards them as vestiges of a once continuous lamina, which formed a winged border to the branched axes of more primitive forms of fronds. It is possible that the pinnules between the pinnae on the rachis of _Archaeopteris_ and the Cyclopteroid leaflets of _Neuropteris_ and _Odontopteris_ may have the morphological significance attributed to them by Potonié. In some cases it is probable that the Aphlebiae, whether vestiges or not, served the purpose of protecting either the whole frond or individual pinnae. Aphlebiae, though especially characteristic of Palaeozoic leaves, are occasionally met with in the form of modified pinnules at the base of the primary pinnae on Mesozoic ferns, e.g. in _Coniopteris hymenophylloides_[1401].

In some fern fronds the lowest pinnule of each pinna differs in shape or size from the normal ultimate segments, but it would be almost affectation to extend the use of the term _Aphlebia_ to such pinnules. The Jurassic species _Cladophlebis lobifolia_ (Phill.) is a case in point[1402]. In this fern, which some authors speak of, without sufficient reason, as _Dicksonia lobifolia_[1403], the lowest pinnule is large and different in shape from the others.

A. _Sphenopteris obtusiloba_. Pinnule. (Enlarged. After Zeiller.)
B, C. _S. obtusiloba_. (⅞ nat. size. After Zeiller.)
D. _Pecopteris arborescens_. (Slightly enlarged. After Zeiller.)
E. _Sphenopteris furcata_ (= _Diplotmema furcatum_). (Slightly
enlarged. After Zeiller.)]

Sphenopteris.

_Sphenopteris_ is one of the many generic names which we owe to Brongniart[1404]. It is the generic designation used for a great number of Palaeozoic and later fronds, most of which are those of true ferns while some Palaeozoic species are undoubted Pteridosperms. The genus, which is purely provisional, includes members of widely different families possessing pinnules of the same general type, such as is represented in some recent species of _Davallia_, _Asplenium_, and other ferns.

The fronds of _Sphenopteris_ may be bipinnate, tripinnate, or
quadripinnate; the rachis may be dichotomously branched or the
branching may be of the pinnate type characteristic of most recent
ferns. The pinnules are small; they vary considerably in shape even
in a single frond, but the chief characteristics are: the lobed
lamina, contracted and often wedge-shaped at the base (fig. 352),
the dichotomously branched veins radiating from the base or given
off from a median rib at an acute angle. The lamina may be divided
into a few bluntly rounded lobes (fig. 352, C) or deeply dissected
into linear or cuneate segments (fig. 352, A, B, E).

Examples of Sphenopteroid leaves have already been described under the genera _Coniopteris_, _Onychiopsis_, _Ruffordia_, etc. Among the numerous examples of _Sphenopteris_ species from the Carboniferous rocks mention may be made of _Sphenopteris obtusiloba_ Brogn.[1405] (fig. 352, A–C), which occurs in the Middle and Lower Coal-Measures of Britain[1406]. This type is characterised by the almost orbicular, oval or triangular pinnules which may reach a length of 15 mm.; they are occasionally entire, but more usually divided into 3 to 5 rounded lobes. The forked veins radiate from the base of the pinnule. The rachis may be dichotomously branched. Fructification unknown.

The species _S. furcata_ Brongn.[1407], characteristic of the Middle and Lower Coal-Measures of Britain (fig. 352, E), is referred to under Stur’s genus _Diplotmema_[1408] in which it is included by some authors solely because of the dichotomous habit of branching of the pinnae.

The pinna represented in fig. 353 illustrates a similar type of pinnule. This species, which is very common in the Calciferous Sandstone of Scotland, was described by Lindley and Hutton as _Sphenopteris affinis_[1409].

The fronds of _Sphenopteris affinis_ were discovered by Mr Peach[1410] in a fertile condition, but he regarded the reproductive organs as those of a plant parasitic on the _Sphenopteris_ fronds. Kidston[1411] substituted Stur’s genus _Calymmatotheca_ for _Sphenopteris_ on the ground that the sporangia figured by Peach under the name _Staphylopteris Peachii_ bear a close resemblance to the organs which Stur described as valves of an indusium in his species _Calymmatotheca Stangeri_[1412]. An examination of Stur’s specimens by Miss Benson[1413] and by Prof. Oliver and Dr Scott has confirmed Stur’s interpretation of the appendages at the tips of the fertile pinnae as valves of an indusial or cupular structure. The superficially similar bodies on the fertile pinnae of _S. affinis_ are however true sporangia, and cannot legitimately be included in the genus _Calymmatotheca_ as described by Stur. For this reason Miss Benson institutes a new genus _Telangium_, the type-species of which, _T. Scotti_ from the Lower Coal-Measures of Lancashire, is based on petrified material. The Scotch species _Sphenopteris affinis_ (= _Calymmatotheca affinis_ of Kidston) is also transferred to _Telangium_; the sporangia are considered by Miss Benson to be microsporangia. This with other species is no doubt correctly included in the Pteridosperms. A complete frond of _Sphenopteris affinis_, showing a regular dichotomy of the main axes, is represented by an admirable drawing in Hugh Miller’s _Testimony of the Rocks_[1414].

Some of the Palaeozoic species of _Sphenopteris_ probably represent the fronds of true ferns, but others are known to have been borne by Pteridosperms. _S. Hoeninghausi_ (fig. 290, C, p. 399) is the foliage of _Lyginodendron_, and Scott[1415] speaks of three species, _S. dissecta_, _S. elegans_, and _S. Linkii_ as the leaves of _Heterangium_. Grand’Eury[1416] has recorded the occurrence in French Coal-Measures of seeds in association with other Sphenopteroid fronds.

Mariopteris, Diplotmema, Palmatopteris.

The discovery of sporangia on the fronds of several Palaeozoic species of _Sphenopteris_ and _Pecopteris_ has led to the institution of new generic names, which indicate an advance in knowledge beyond the stage implied by the use of those provisional designations based solely on the form and venation of the pinnules. Other names have been created by authors in place of _Sphenopteris_ and _Pecopteris_ on the ground that a striking feature in the mode of branching of fronds is sufficiently important to justify generic recognition even in the absence of fertile specimens. As examples of designations based primarily on the branch-system of compound leaves, the genera _Mariopteris_, _Diplotmema_, and _Palmatopteris_ may be briefly considered (fig. 354 A–C). Dr Kidston[1417] is of opinion that the creation of new genera for purely vegetative characters of fronds is of no real advantage, and he prefers to retain the older provisional names for species known only in the sterile condition. On the other hand, if we are sufficiently familiar with specimens large enough to enable us to recognise a well-defined morphological character, it may serve a useful purpose to employ a generic designation for features which may have a phylogenetic value. A comparative examination of Palaeozoic, Mesozoic, and recent compound fronds, including both Pteridosperms and true ferns, brings to light certain distinguishing features characteristic of the older types which, as Potonié maintains[1418], point to the derivation of the pinnate habit from a primitive dichotomous system of branching. For a more complete discussion of this question reference should be made to Potonié’s suggestive papers. Among recent ferns _Matonia_ and _Dipteris_, two survivals from the past, afford instances of fronds with a branching system of the dichotomous type.

Similarly, in _Gleichenia_, _Lygodium_, and more rarely in species of Polypodiaceae (_e.g._ _Davallia aculeata_, fig. 232) dichotomy is a striking feature of the fronds. In the great majority of recent ferns the fronds have assumed a pinnate habit. Among Palaeozoic fern-like fronds dichotomous branching of the main rachis and of the pinnae is much more common. Potonié draws attention to several other features which distinguish Palaeozoic fronds from the majority of later species: the frequent occurrence of pinnules borne directly on the main rachis (fig. 354, D), and of modified pinnules or Aphlebiae on the rachis and petiole, are characters to which he attributes an evolutionary significance. The main point is that a comparative examination of leaf-form affords evidence in favour of the view that the modern type of frond, with its naked rachis bearing two rows of pinnae, has been derived from a less specialised type in which the distinction between the parts of the leaf is much less evident. The primitive leaf was probably a dichotomously branched axis provided with a continuous lamina which eventually became broken up into separate lobes or pinnules.

As the dichotomy of the frond became less regular, a pinnate habit was acquired, as is clearly seen in many Palaeozoic types which constitute connecting links between forked and pinnate fronds (fig. 354, D). The Aphlebiae may be remnants of the once-continuous lamina on the petiole, and the normal pinnules borne on the rachis may be regarded as the attributes of fronds in which the division of physiological labour had not reached the stage which characterises the leaves of recent ferns.

_Mariopteris._

This name, which is due to Zeiller[1419], is applied by him to Palaeozoic fronds characterised by a double bifurcation of the rachis of the primary pinnae. _Mariopteris muricata_ (= _Pecopteris muricata_ Schloth.) may be taken as the type of the genus. This species is common in the Lower and Middle Coal-Measures of Britain and rare in the Upper Coal-Measures[1420]. It is described by Kidston[1421] as one of the most polymorphic and widely distributed Coal-Measure species. The pinnules as seen in fig. 364, B, are of the Sphenopteroid type. No fertile specimens are known, but it is significant that Grand’Eury[1422] has recorded the association of _Mariopteris muricata_ and seeds.

The main rachis gives off alternate naked branches, each of which bifurcates at its apex into two short naked axes, and these are again forked, the ultimate branches having the form of bipinnate pinnae provided with large Sphenopteroid pinnules (fig. 354, B). Zeiller includes in _Mariopteris_ some species which Stur[1423] referred to his genus _Diplotmema_. Possibly some of the Palaeozoic fronds with a zigzag rachis may have been climbers like _Lygodium_.

A. _Palmatopteris._
B. _Mariopteris._ (A, B, after Potonié.)
C. _Diplotmema Zeilleri_, Stur. (After Zeiller.)
C′. _D. Zeilleri._ Pinnule. (× 3. After Zeiller.)
D. _Neuropteris macrophylla._ (British Museum.)
D′. _N. macrophylla._ Pinnule. (Slightly enlarged. After Kidston.)
E. _N. heterophylla._ Pinnule. (Slightly enlarged. After Zeiller.)
F. _N. Scheuchzeri._ (Slightly reduced. After Kidston.)
G. _Alloiopteris Essinghii._ (Enlarged. After Potonié.)]

_Diplotmema._

This generic name is employed by Zeiller[1424] and other authors in a more restricted sense than that in which it was originally used by Stur. The Upper Carboniferous species _Sphenopteris furcata_ Brongn. (fig. 352, E) may serve as the type. This species occurs in the Middle and Lower Coal-Measures of Britain[1425]. The main rachis gives off branches as in _Mariopteris_, but in _Diplotmema_ each naked lateral branch is forked at its apex into two opposite pinnae bearing deeply dissected Sphenopteroid pinnules. Zeiller[1426] and Stur have recorded fertile specimens of _Diplotmema_, but in no case have actual sporangia been discovered. In the species _Diplotmema Zeilleri_ Stur (fig. 354, C, C′) two Aphlebiae occur at the base of each secondary axis[1427]. It has been pointed out by Potonié that in _Diplotmema furcatum_ the equal dichotomy of the lateral branches is not characteristic of the frond as a whole. In the case of branches higher on the rachis the dichotomy becomes unequal and the forked axis is gradually replaced by a simple pinna (fig. 354, A). For this type of frond, Potonié proposed the generic name _Palmatopteris_ in place of _Diplotmema_, which he discards. The long comparatively slender rachis of _P. furcata_ suggests comparison with the liane species of _Lygodium_[1428].

A. _Cephalotheca mirabilis_, Nath. Fertile pinnae. (Partially
restored. After Nathorst.)
B. _C. mirabilis._ Sterile pinnule. Nat. size. (After Nathorst.)]

Cephalotheca.

This genus was proposed by Nathorst[1429] for some peculiar bipinnate fertile fronds from the Upper Devonian rocks of Bear Island. The pinnae bear slender forked ultimate segments represented by a few detached fragments (fig. 355, B), associated with the rachises. The fertile pinnae are given off in opposite pairs from the main axis over which they are concrescent (fig. 355, A). A mop-like cluster of sporangia is borne on the lower surface and close to the base of a fertile pinna: the exannulate sporangia are compared with those of _Scolecopteris_. Nathorst compares _Cephalotheca_ with a Belgian species of Upper Devonian age described by Crépin[1430] as _Rhacophyton condrusorum_ and by Gilkinet[1431] as _Sphenopteris condrusorum_. A similar fossil is also described by Baily[1432] as _Filicites lineatus_ from the Kitorkan Grits of Ireland.

The position of _Cephalotheca_ cannot be definitely determined from the available data, but it is more probable that it was a seed-bearing Pteridosperm and not a true fern. Zeiller[1433] has recently expressed the same opinion.

Thinnfeldia.

The genus _Thinnfeldia_, founded by Ettingshausen in 1852[1434] on some Hungarian Liassic specimens, though frequently included in the Filicales, cannot be said to occupy that position by virtue of any well-authenticated filicinean features. It is by no means improbable that many of the species referred to this genus are closely allied to Palaeozoic Pteridosperms.

_Thinnfeldia_ may be briefly defined as follows:

Fronds simple and pinnatifid, pinnate or bipinnate: rachis broad
and occasionally dichotomously branched. Pinnules often fleshy or
coriaceous; broadly linear, entire or lobed, provided with a midrib
from which simple or forked secondary veins are given off at an
acute angle: or the laminae may be short and broad without a midrib
and traversed by several slightly divergent and forked veins.

No satisfactory evidence of reproductive organs has so far been
adduced.

The genus is chiefly characteristic of Upper Triassic, Rhaetic, and Jurassic floras, though it was in all probability represented in Permian floras. Several species, many of which are valueless, are recorded also from Cretaceous and Tertiary formations. Search should be made for fertile specimens or for evidence as to the association of seeds with _Thinnfeldia_ fronds.

Some Permian fossils from Kansas which Sellards[1435] has made the type of a new genus, _Glenopteris_, appear to be indistinguishable generically from leaves of Lower Mesozoic age universally recognised as typical examples of _Thinnfeldia_.

_Thinnfeldia odontopteroides_ (Morris)[1436]. Figs. 356–358.

This is a very variable species as regards the shape and size of the ultimate segments and their venation. It is a type of extended geographical range characteristic of Rhaetic or Upper Triassic rocks in Australia, South Africa, India, South America, and various European localities.

Frond bipinnate; the broad rachis may be dichotomously branched.
Pinnules with a thick lamina which may be almost semicircular in
form, deltoid, broadly oval or broadly linear, and often confluent
at the base. Short and broad pinnules occur on some fronds directly
attached to the main rachis between the pinnae. The longer and
narrower pinnules (fig. 356, C), resembling those of the Palaeozoic
genus _Alethopteris_, have a well-defined midrib, while the smaller
segments are characterised by several slightly divergent veins
which spring directly from the rachis (fig. 356, A). Epidermal
cells polygonal or, above the veins, rectangular in shape; stomata,
which are slightly sunk, occur on both the upper and lower
epidermis. Fertile specimens unknown.

The portion of a lobed pinnule shown in fig. 356, B, illustrates a form of segment intermediate between the linear type with a midrib and a row of shorter pinnules without a median vein. Fig. 356, D, represents another instance of variation in the arrangement of the veins in segments of different sizes. Various specific and generic names have been assigned to Thinnfeldia fronds of Rhaetic age on the ground of the occurrence of pinnules longer and narrower than those usually associated with _T. odontopteroides_; but in view of the range of variation met with in a single leaf it is advisable to extend rather than to restrict the boundary of what we are pleased to regard as a specific type.

A–D. _Thinnfeldia odontopteroides_ (Morris).
E. _Ptilozamites._ (E, after Nathorst.)]

The name _Thinnfeldia lancifolia_ has been applied by Morris to fossils from Australia which may be identified with _T. odontopteroides_, and the same designation is employed by Szajnocha and by Solms-Laubach[1437] for Rhaetic specimens from South America. Similar fronds are described by Geinitz[1438] as _Thinnfeldia tenuinervis_ from Argentine Rhaetic strata. _Odontopteris macrophylla_ Curran, _T. falcata_ Ten.-Woods, _Gleichenia lineata_ Ten.-Woods, and _Cardiopteris Zuberi_ Szaj. afford other examples of what are probably closely allied forms[1439].

Some exceptionally large examples of _T. odontopteroides_ are figured by Feistmantel[1440] from the Hawkesbury series of New South Wales in which the bipinnate frond has a breadth of 25–30 cm. A specimen from the Molteno beds of South Africa, probably of Rhaetic age, represented in fig. 357, illustrates a smaller leaf with pinnules of the linear type, some of which are partially divided into shorter pinnules with forked veins. The example represented in fig. 358, from Cyphergat (S. Africa), shows two equal branches of a rachis with small contiguous segments.

Some specimens figured by Zeiller[1441] from the Rhaetic strata of Tonkin as _Pecopteris (Bernouillia?_) sp. may be portions of _Thinnfeldia_ fronds, and the large leaves which he refers to _Ctenopteris Sarreni_ differ but slightly from the Australian specimens described by Feistmantel as _T. odontopteroides_.

_Thinnfeldia rhomboidalis_, Ettingshausen. Figs. 359, 360, C.

Under this name Ettingshausen described the type-specimen of the genus from Lower Lias strata at Steierdorf in Hungary. He assigned the plant to the Coniferae on the ground of a resemblance of the pinnules to the phylloclades of _Phyllocladus. Thinnfeldia rhomboidalis_ bears a close resemblance to _T. odontopteroides_, but the pinnules are usually longer and narrower, as shown in the English specimen from the Lower Lias of Dorsetshire represented in fig. 359. The darker margin of the pinnules shown in fig. 360, C, gives the impression of a revolute lamina, but a microscopical examination points to a thicker cuticle at the edge of the segments.

]

The species is recorded from Jurassic rocks of France, Germany, Italy, India, Australia, and elsewhere[1442].

Palaeobotanical literature contains numerous records of Jurassic, Cretaceous and some Tertiary species referred to _Thinnfeldia_, but many of these are probably not generically identical with _T. odontopteroides_ or _T. rhomboidalis_. Mr Berry[1443] in a paper on _The American species referred to Thinnfeldia_ concludes that the genus is “a rather indefinite one ... and badly in need of revision.” He regards the Middle and Upper Cretaceous American species as Conifers related to _Phyllocladus_ and probably forming a link between the Podocarpeae and Taxeae: for these forms he proposes the generic name _Protophyllocladus_. The opinion has been expressed elsewhere[1444] that this “problematical[1445]” genus rests on an unsatisfactory basis; the available data do not justify the use of a name which implies the existence in North American Cretaceous floras of a type related to the New Zealand and Tasmanian Conifer _Phyllocladus_. We are not in a position to assign a single species of _Thinnfeldia_ to the Filicales or the Gymnosperms.

A leaflet from Jurassic rocks of Poland figured by Raciborski[1446] shows what this author regards as the impression of a circular sorus: no sporangia have been found. A specimen in the British Museum[1447], which is said to come from Rhaetic beds in Queensland, shows a row of contiguous polygonal prominences on each side of the midrib which resemble the sori of a fern; but until sporangia are discovered we cannot determine the precise nature of this apparently fertile frond.

A species described by Fontaine[1448] from the Potomac beds (Wealden-Jurassic) of North America as _Thinnfeldia variabilis_ affords a good example of a plant which cannot be identified with any degree of confidence either as a fern or a seed-bearing type. Mr Berry draws attention to the former application of this name by Velenovský to a distinct Lower Cretaceous Bohemian species and proposes for Fontaine’s plant the name _T. Fontainei_; he maintains that no one has doubted the fern-nature of the Potomac plant. _T. variabilis_ may indeed be a fern, but the evidence is not such as to preclude legitimate doubts as to the correctness of this suggestion. Solms-Laubach[1449], in referring to Schenk’s view that _Thinnfeldia_ and its allies may represent a group intermediate between Ferns and Gymnosperms, admits that it is a possible supposition; he is, however, inclined to consider _Lomatopteris_ and _Cycadopteris_, “genera especially comparable with _Thinnfeldia_” as more probably ferns.

At this point we may conveniently consider a series of genera which occupy an equally uncertain position and bear a very close resemblance to _Thinnfeldia_.

A. _Lomatopteris jurensis_. (⅞ nat. size. After Kurr.)
B. _L. Schimperi_. (⅞ nat. size. After Salfeld.)
C. _Thinnfeldia rhomboidalis_, Ett. (Slightly enlarged. British
Museum. No. 52672.)]

Lomatopteris.

The generic name _Lomatopteris_ was proposed by Schimper[1450] for some bipinnate fronds originally described by Kurr[1451] from Jurassic rocks of Württemberg as _Odontopteris (?) jurensis_ (fig. 360, A). I have elsewhere expressed the opinion[1452] that this German species may be identical with _Thinnfeldia rhomboidalis_ Ett. Kurr’s type-specimen, a portion of which is reproduced in fig. 360, A, consists of a frond or large pinna characterised by a prominent and broad rachis giving off alternate linear pinnae bearing bluntly rounded, contiguous and basally concrescent pinnules having a thick or revolute border and a central rib. The lateral veins are visible in the ultimate segments of Kurr’s fossil. Saporta[1453] has described several species, which he refers to Schimper’s genus, from French Jurassic strata: it is, however, difficult to recognise some of the examples represented in his illustrations as specifically distinct forms. This author notices the resemblance of _Lomatopteris_ to _Thinnfeldia_, not only in habit but in the structure of the epidermal cells[1454]. In _Lomatopteris_ and in _Thinnfeldia_ the cells have straight and not sinuous walls and the slightly sunken stomata are surrounded by a ring of epidermal cells. Salfeld[1455] has recently described portions of fronds from Jurassic rocks of South-West Germany, which he identifies as _Lomatopteris jurensis_. He disagrees with my view that _Lomatopteris_ does not differ sufficiently from _Thinnfeldia_ to be accorded generic autonomy, chiefly on the ground that the folded-over edge of the pinnules is a distinguishing feature of _Lomatopteris_. There is, however, no difference, in appearance at least, between the leaflets of some species of _Thinnfeldia_, e.g. _T. rhomboidalis_ from Liassic rocks of England[1456], and those referred to _Lomatopteris_. In a later paper, Salfeld[1457] describes some Portlandian fragments from North Germany as _Lomatopteris Schimperi_, identifying them with a Wealden fossil of somewhat doubtful affinity, which Schenk[1458] makes the type of his species. The Portlandian specimens are described as tripinnate, with thick decurrent obtusely terminated pinnules with a revolute edge. The general form of the frond is very similar to that of _L. jurensis_. Salfeld publishes a photograph of a large specimen which he describes as fertile and a drawing of a piece of a pinna: the latter is reproduced in fig. 360, B. He speaks of sori occurring in two rows, probably attached to lateral veins, in the groove between the midrib and the revolute edge of the lamina. The sporangia are described as “nicht näher bekannt[1459].” An examination of the figures reveals nothing as to the nature of the “sori.” The specimens are considered by Salfeld to afford decisive evidence against the view that _Lomatopteris_ and _Thinnfeldia_ are generically identical. Nothing has so far been published which constitutes a valid argument in favour of retaining Schimper’s generic name.

Cycadopteris.

Zigno[1460] founded the genus _Cycadopteris_ on Italian Jurassic impressions regarded by Schimper as indistinguishable from _Lomatopteris_. As Solms-Laubach[1461] points out, the supposed sori of _Cycadopteris_ described by Zigno are not convincing. There appear to be no satisfactory reasons for separating _Cycadopteris_ from _Lomatopteris_, nor do the fronds described under these names exhibit any important differences from _Thinnfeldia_.

Ptilozamites.

Nathorst[1462] founded this genus on a remarkable series of specimens from the Rhaetic Coal-beds of Scania and assigned it to the Cycadophyta. The species _Ptilozamites Heeri_ may be taken as a representative type. The leaves are linear and simply pinnate. In the example shown on a much reduced scale in fig. 361 the frond is 53 cm. long and 2·1 cm. broad. The upper edge of each pinnule is straight or slightly concave; the lower edge is rounded; the veins are slightly divergent and dichotomously branched (fig. 356, E, p. 539). In some of Nathorst’s specimens the broad rachis is forked as in many Thinnfeldias.

As a comparison of fig. 356, A and E, shows, the pinnules of some specimens of _Thinnfeldia odontopteroides_ are identical with those of _Ptilozamites_. In the latter genus the rachis is either unbranched or occasionally forked, while in _Thinnfeldia_ the branching may be of the dichotomous or pinnate type. In _Ptilozamites_ the segments appear to be always without a midrib, while a median vein frequently occurs in those of _Thinnfeldia_. There can be little doubt as to the very close alliance between the Rhaetic species referred to these two genera. The name _Ptilozamites_ should perhaps be retained for such long and narrow fronds as that shown in fig. 361: no species included in _Thinnfeldia_ is known in which the rachis reached so great a length without branching. The habit of _Ptilozamites Heeri_ predisposes one in favour of Nathorst’s opinion that the fronds are Cycadean: we have no information in regard to the nature of the reproductive organs.

Ctenopteris.

This name was instituted by Saporta[1463], at Brongniart’s suggestion, for Liassic species characterised by pinnules like those of _Thinnfeldia_, but distinguished by the bipinnate habit of the frond. Saporta compares the genus with the Palaeozoic leaves known as _Odontopteris_, and with Italian Jurassic plants referred by Zigno to his genus _Dichopteris_.

The name _Ctenozamites_ is applied by Nathorst[1464] to the type of frond which Saporta, Zeiller, and other authors refer to _Ctenopteris_. Nathorst instituted _Ctenozamites_ for fossils agreeing in the form and venation of the pinnules with his genus _Ptilizamites_ but differing in being bipinnate and not pinnate.

Fronds of _Ctenopteris_ are characteristic of the Jurassic and Rhaetic series; they are known only in the sterile condition. As Zeiller[1465] says, _Ctenopteris_ may be a member of the Cycadofilices, an extinct group founded on Palaeozoic plants combining Cycadean and Filicinean characters, and some of which are now known to be Pteridosperms. It is probable that the genus is not a true fern: it is more likely to be a member of the Cycadophyta or of some generalised extinct group.

_Ctenopteris cycadea_ (Brongniart). Fig. 362.

1828. _Filicites cycadea_, Brongniart, Hist. Vég. foss. p. 387, Pl.
CXXIX.

1832. _Odontopteris cycadea_, Berger, Verstein. Coburg Geg. p. 23,
Pl. III.

1873. _Ctenopteris cycadea_, Saporta, Pal. Franç. Vol. I. p. 355,
Pls. XL. XLI.

Frond bipinnate, broad rachis giving off branches at an acute
angle; pinnules broadly linear, slightly falcate, with several
slightly divergent forked veins.

A frond very similar to the Lower Lias specimen from Dorsetshire represented in fig. 362 was described by Leckenby as _Ctenis Leckenbyi_ (Bean MS.) from the Inferior Oolite of Yorkshire[1466]. Leckenby recognised the possibility of a Cycadean affinity, but regarded the bipinnate habit as an objection. The branched fronds of the Australian Cycad _Bowenia_ supply an answer to this objection. Several good examples of _Ctenopteris cycadea_ are figured by Schenk[1467] from Rhaetic rocks of Persia. Zeiller’s Tonkin Rhaetic species, _C. Sarrani_[1468], affords a striking illustration of the difficulty of drawing a clear line of separation between _Ctenopteris_ and some species of _Thinnfeldia_.

]

_Ctenopteris_ is in all probability very closely related to _Thinnfeldia_ and _Ptilozamites_.

Dichopteris.

This genus was proposed by Zigno[1469] for some large specimens from the Jurassic plant-beds of Northern Italy.

The bipinnate leaves are characterised by the great breadth of the
rachis which is dichotomously branched in the distal region (fig.
363); the linear pinnae reach a considerable length. Pinnules
relatively small, oblong and slightly contracted at the base; the
decurrent and confluent lamina forms a narrow wing to the main
axis. Veins slightly divergent and forked, as in _Ptilozamites_.

_Dichopteris visianica_, Zigno. Fig. 363.

A specimen of this species in the Padua Museum has a total length of 83 cm. It has been elsewhere suggested[1470] that a fragment figured by Zigno as a fertile example of this type is probably part of a frond of the Osmundaceous fern _Todites_. Since this opinion was expressed I have had an opportunity of examining the actual specimen at Padua: the circular patches described by Zigno as sori appear to be irregularities in the matrix and not an original feature.

Brongniart[1471] instituted the genus _Pachypteris_ for some imperfectly preserved English Jurassic fossils from Whitby, which he described as _P. lanceolata_. Specimens have since been described[1472] from the Inferior Oolite rocks of the Yorkshire coast. Brongniart described the pinnules as being without veins or as possessing only a midrib. It is almost certain that the apparent absence of veins in most specimens[1473] is due to the fleshy nature of the segments and that the species _P. lanceolata_ should be transferred to _Dichopteris_.

Krasser[1474] has described a species from Cretaceous rocks of the island of Lesina, off the Dalmatian coast, as _Pachypteris dalmatica_ which is very similar in habit to the English specimens and to Zigno’s _Dichopteris visianica_. One of Krasser’s specimens is practically identical with _Dichopteris lanceolata_ (Brongn.), while in others the small pinnules are replaced in some of the pinnae by a continuous lamina with a few distal serrations. The latter form a link between the _Dichopteris_ and _Thinnfeldia_ type of segment. Krasser gives a full résumé of opinions expressed by other authors in regard to the position of _Pachypteris_ (= _Dichopteris_) and decides in favour of a Cycadean alliance.

A French Jurassic plant which Saporta[1475] made the type of a new genus _Scleropteris_, and described as _S. Pomelii_, appears to be indistinguishable from _Dichopteris_.

_Dichopteris_, though conveniently retained as a distinct genus, agrees so closely, in the broad and forked rachis and in the fleshy pinnules, with _Thinnfeldia_ that it would seem reasonable to regard the two genera as members of the same group.

Several authors have drawn attention to the striking resemblance in form and venation between the fronds of the Palaeozoic genus _Odontopteris_ and those of _Ctenopteris_ and _Thinnfeldia_. In _Odontopteris_, as in _Neuropteris_, another Palaeozoic genus, the rachis occasionally bifurcates as in _Thinnfeldia_ and _Dichopteris_, and the ultimate segments of some species of _Odontopteris_ (fig. 366, A) are practically identical with those of _Thinnfeldia_ and _Ptilozamites_.

_Odontopteris_ is probably a Pteridosperm. There is no adequate reason for supposing that this group of plants which played a prominent part in the Permo-Carboniferous floras was no longer in existence during the Mesozoic era.

Odontopteris.

Brongniart[1476] instituted the genus _Odontopteris_ for compound fronds from the Coal-Measures characterised by pinnules attached by the whole breadth of the base and traversed by numerous forked veins. _Odontopteris_ is very rare in British Carboniferous rocks and “appears to be restricted to the Middle and Upper Coal-Measures[1477].”

A. _Alethopteris lonchitica_ (Schloth.). ½ nat. size.
B. _Mariopteris muricata_ (Schloth.). × 2.
C. _Odontopteris_ cf. _alpina_ (Presl). ⅗ nat. size.
D. _O_. cf. _alpina_. Portion of pinna enlarged.

(A–D. From photographs by Dr Kidston.)]

Fronds large, bipinnate or tripinnate, the main rachis, which
may be dichotomously branched, bears long linear pinnae with
broadly linear or deltoid pinnules, acute or blunt, attached
by the whole of the base; the lower margin of the lamina,
which is usually entire and rarely lobed (e.g. _Odontopteris
osmundaeformis_)[1478], is often decurrent on the axis of the
pinna. The basal pinnule of each pinna is frequently attached by
a contracted base, and the lamina may differ in form from that of
the normal segments. Pinnules often occur on the main rachis,
and in some species the petiole bears modified pinnules which are
larger than the ultimate segments of the pinnae and in some cases
Cyclopteroid in shape. The pinnules are traversed by numerous
dichotomously branched veins; if a midrib is present it dies out in
the basal part of the lamina. In some species (genus _Mixoneura_)
pinnules of the Neuropteroid type, characterised by a well-defined
midrib, occur in association with typical Odontopteroid pinnules on
the same pinna.

]

The species represented in fig. 364, C, D, from the Middle Coal-Measures of Barnsley, Yorkshire, illustrates the form and venation of the _Odontopteris_ type of pinnule. Another species, _O. Reichiana_ Gutb.[1479], is also recorded by Kidston from the Lower Coal-Measures of Lancashire. Some unusually good specimens of the type-species of the genus _Odontopteris minor_, Brongn., have been figured by Zeiller[1480] from the Coal-Measures of Blanzy (fig. 365) which show the dichotomy of the main axis and the occurrence of Aphlebiae on the petiole. The late Dr Weiss[1481] divided _Odontopteris_ into two sections, _Xenopteris_ and _Mixoneura_, the pinnules of the former having the form shown in fig. 364, D; while in species of the latter sub-genus some of the pinnules are identical in form and venation with those of _Neuropteris_ except that they are attached by the whole breadth of the base. Zeiller[1482] employs _Mixoneura_ as a generic designation. In an American species _O. Wortheni_ Lesq.[1483] the pinnules bear numerous hairs like those on some species of _Neuropteris_ (fig. 373, p. 570). The large size of the fronds of _Odontopteris_ suggested to Weiss[1484] that they were borne on the stems of tree-ferns, but Grand’Eury’s[1485] examination of specimens in the Coal-beds of central France led him to picture the plant as bearing a tuft of leaves on a short subterranean stem. Renault and Zeiller[1486], on the other hand, obtained evidence in the Commentry Coal-field of fronds borne on elongated stems which grew on the ground and were supported by stronger plants. Stur[1487] was the first to suggest that _Odontopteris_ should be excluded from the ferns. Grand’Eury’s[1488] supposed fertile pinnules of _Odontopteris_ do not afford any satisfactory evidence of the sporangial nature of the small swellings which he figures at the ends of the veins. This author pointed out several years ago that the petioles of some species of _Odontopteris_ possess the anatomical features of _Myeloxylon_, a type of leaf-stalk which is now known to belong to Pteridosperms. In a recent paper Grand’Eury[1489] records the association of _Odontopteris_ fronds with small seeds (_Odontopterocarpus_), a discovery which leaves little or no doubt as to the Pteridospermic nature of the genus. The fronds of _Odontopteris_ are very similar in habit to those of _Neuropteris_, another Pteridospermic genus.

The similarity between some _Odontopteris_ and _Thinnfeldia_ leaves, to which attention has already been called, is well illustrated by _O. genuina_ Grand’Eury[1490], a pinnule of which is represented in fig. 366, A. _Odontopteris_ is a fairly widespread genus in Upper Carboniferous and Lower Permian rocks, and is recorded also from Triassic strata: it is represented in the Coal-fields of North America and in several parts of Europe[1491].

In some fronds included in _Odontopteris_ the pinnae are characterised by a broad irregularly lobed lamina which also forms a winged border to the rachis. Examples of this form are afforded by _Odontopteris Browni_ Sew.[1492] from the Burghersdorp Series (Triassic?) of Cape Colony, and _O. Fischeri_ described by Brongniart[1493] from the Permian of Russia. The Russian species would perhaps be more appropriately placed in the genus _Callipteris_, as Weiss[1494] suggests; the absence of venation in _O. Browni_ renders generic identification unsatisfactory.

A. _Odontopteris genuina_ (Grand’Eury). (× 2⅝. After Renault and
Zeiller.)
B. _Callipteridium gigas_ (Gutb.). (× 2⅝. After Zeiller.)
C. _Callipteris Pellati_ (Zeill.). (× 1¾. After Zeiller.)
D. _C. lyratifolia_ (Goepp.). (× 1¾. After Zeiller.)]

Callipteris.

Brongniart[1495] instituted this genus for certain species of supposed ferns previously referred to the genera _Pecopteris_, _Alethopteris_, and _Neuropteris_. _Callipteris_ is a characteristic Permian plant which is almost certainly a Pteridosperm. Zeiller has pointed out that such descriptions of fertile specimens as have been written are unsatisfactory. A few years ago, however, Grand’Eury[1496] recorded the occurrence of seeds in association with Callipteris fronds in the Autun district, and in some cases they were found attached to the pinnae and rachis. The seeds are ovoid or spherical (5–10 mm. broad) and smaller than those of _Neuropteris_. The drawings of fertile segments published by Weiss[1497] afford no indication of reproductive organs. Potonié[1498] figures some pinnules of _Callipteris conferta_ in which the thick lamina is covered with sinuous grooves probably made by some insect larvae: as he suggests, similar markings may have been mistaken for the remains of sori. The occurrence of _Callipteris_ fronds recorded by Weber and Sterzel[1499] in association with _Medullosa_ stems in the Lower Permian of Saxony is in accordance with Grand’Eury’s conclusion.

Fronds reaching 1 metre in length, bipinnate or tripinnate, main
rachis frequently exhibiting a combination of dichotomous and
pinnate branching. Pinnae linear, usually crowded, decurrent on the
rachis; the pinnules on the lower side of the pinnae are continued
on to the rachis. Pinnules of the Pecopteroid type, entire or
slightly lobed, or of the Sphenopteroid type and more or less
deeply dissected (fig. 366 C, D), the lamina of adjacent pinnules
concrescent; on the lower pinnae the lamina may be continuous as in
an Alethopteris pinnule. A midrib may extend almost to the bluntly
rounded apex of the ultimate segments, giving off oblique, simple,
or forked veins, the lowest of which arise directly from the
rachis; in the Sphenopteroid forms the lateral veins are given off
at a more acute angle.

A striking feature of the genus is the occurrence of pinnules on the main rachis, as in _Odontopteris_. Zeiller has wisely extended the application of _Callipteris_ to fronds possessing this character irrespective of the entire or lobed form of the ultimate segments. He found among the numerous examples of the genus obtained from Autun[1500] and Lodève[1501] transitional forms connecting such species as _C. conferta_ (fig. 367) and _C. Pellati_ Zeill. (fig. 366, C) in which the Pecopteroid pinnules are slightly lobed, with _C. lyratifolia_ (Goepp.) (fig. 366, D), _C. flabellifera_[1502] (Weiss), and _C. Bergeroni_ Zeill. characterised by deeply lobed Sphenopteroid segments.

_Callipteris conferta_ (Sternberg)[1503]. Fig. 367.

1723. Scheuchzer, Herb. Diluv. Pl. II., fig. 3.

1826. _Neuropteris conferta_, Sternberg, Flor. Vorwelt, p. 17.

1849. _Callipteris conferta_, Brongniart, Tableau, p. 24.

This polymorphic species (fig. 367) is one of the most characteristic Permian plants. The oval-linear pinnules, attached by the whole base, occur on both pinnae and rachis; this feature, the thick texture of the lamina, and the linear, obliquely set, pinnae render the fronds easily recognisable. The fronds bore seeds.

In a recent account of some Permian plants from Germany, Schuster[1504] refers a portion of a frond to _Callipteris conferta_ (Sternberg) var. _polymorpha_ Sterzel, which is characterised by unusually large and polymorphic pinnules. In size and shape the pinnules recall those of _Neuropteridium validum_ Feist.

Callipteridium.

The name _Callipteridium_, created by Weiss[1505] as a sub-genus of _Odontopteris_, is applied by Zeiller and other authors to a few Upper Carboniferous and Permian species characterised by the occurrence of simply pinnate pinnae on the main rachis between the bipinnate primary pinnae. Single pinnules are borne directly on the rachis of the primary pinnae between the pinnate branches. The form and venation of a typical pinnule are shown in fig. 366, B. _Callipteridium pteridium_, originally recorded by Schlotheim as _Filicites pteridius_[1506], has been fully described by Renault and Zeiller from unusually large specimens found in the Commentry Coal-field[1507]. This species illustrates the peculiar morphological features of the genus. The main rachis of the tripinnate fronds, several metres long, shows a combination of dichotomous and pinnate branching; from the zigzag and forked axis are given off bipinnate pinnae and, between these, shorter pinnate branches. The pinnules closely resemble those of _Callipteris conferta_ but reach a greater length; the pinnules borne on the rachises of the lateral branches differ from the others in their broader base and more triangular lamina.

No fertile specimens have been found. It is probable that _Callipteridium_ was not a true fern, and that White[1508] is correct in including it among the Pteridosperms.

Archaeopteris.

In 1852 Forbes[1509] published a brief description of some supposed fern fronds, found by the Geological Surveyors of Ireland in Upper Devonian rocks of Kilkenny, under the name _Cyclopteris hibernica_. The Irish specimens were more fully described by Baily[1510] in 1858. Fronds of the same type were referred by other authors to _Cyclopteris_, _Adiantites_ or _Noeggerathia_, until Schimper[1511] proposed the generic name _Palaeopteris_ on the ground that the fronds described by Forbes and Baily are distinguished by the nature of their fertile pinnae from the sterile leaves included in Brongniart’s provisional genus _Cyclopteris_. The earlier use of _Palaeopteris_ by Geinitz for an entirely different plant led Dawson[1512] to institute the genus _Archaeopteris_. The genus _Archaeopteris_ may be defined as follows:

Fronds bipinnate, reaching a considerable length (90 cm.); the
stout rachis bears long linear pinnae; sterile pinnules obovate
or cuneate with an entire, lobed, fimbriate, or laciniate lamina
traversed by divergent dichotomously branched veins. The fertile
pinnae usually occur on the lower part of the rachis; pinnules with
a much reduced lamina bear numerous fusiform or oval exannulate
sporangia (fig. 369, A, E, H), sessile or shortly stalked,
singly, or in groups of two or three. The base of the petiole is
characterised by a pair of partially adnate stipules (fig. 369,
C, D), and single pinnules or scales occur in some species on the
rachis between the pinnae and on the petiole.

_Archaeopteris hibernica_ (Forbes). Figs. 368, 369, A–C.

The specimen from Kilkenny represented in fig. 368 has a length of over 80 cm. The upper pinnae bear numerous imbricate obovate pinnules (fig. 369, A, B) with an entire or very slightly fimbriate margin, while on the shorter lower pinnae the ultimate segments are reduced to a slender axis bearing numerous fusiform sporangia, 2–3 mm. in length. Kidston[1513] has pointed out that sporangia occasionally occur on the edge of ordinary pinnules, and he first recognised the stipular nature of the scale-like appendages which Baily noticed on the swollen petiole base (5 cm. broad) of the Irish species (fig. 369, C). Restorations of _Archaeopteris hibernica_ have been figured by Baily[1514] and by Carruthers[1515], but the description of the fertile pinnae by the latter author requires modification in the light of Kidston’s description of the Dublin specimens.

• • • • •

_Archaeopteris_ is recorded from Upper Devonian rocks of the South of Ireland, Belgium, Germany, Southern Russia, Bear Island, and Ellesmere Land in the Arctic regions, Canada, Pennsylvania, and elsewhere. Many of the specimens described under different names bear a close resemblance, which in some cases probably amounts to specific identity, to _A. hibernica_. _A. Jacksoni_ originally described by Dawson[1516] and more recently by Smith and White[1517] from Devonian rocks of Maine, the Canadian type _A. gaspiensis_ Daws., and some species figured by Lesquereux[1518] from Pennsylvania, are examples of forms which present a striking similarity in habit to the Irish species. The Belgian Devonian fossils named by Crépin[1519] _Palaeopteris hibernica_ var. _minor_ are regarded by him as probably identical with Goeppert’s species _Cyclopteris Roemeriana_ from the neighbourhood of Aachen. Heer recorded _Archaeopteris Roemeriana_ from Upper Devonian beds in Bear Island, and Nathorst[1520], who has published a more complete account of the Arctic forms, draws attention to the resemblance of some of them to _A. hibernica_. A species described by Schmalhausen[1521] from the Upper Devonian of Southern Russia as _A. archetypus_ (fig. 369, D) appears to differ from _A. hibernica_ in the slightly less reduced lamina of the fertile segments. This species has been more adequately illustrated by Nathorst[1522] from material collected in Ellesmere Land: he is unable to confirm Schmalhausen’s statement that the pinnae are spirally disposed.

The species _A. fimbriata_ (fig. 369, G) described by Nathorst from Bear Island is characterised by the more deeply dissected lamina of the sterile pinnules. In _A. fissilis_ Schmal. from Russia and Ellesmere Land the lamina (fig. 369, E, F) is cut up into filiform segments: a fertile pinnule of this species is represented in fig. 369, E.

Some sterile impressions figured by Krasser[1523] from Palaeozoic strata (Lower Carboniferous or Upper Devonian?) in the province of Nanshan in China as _Noeggerathia acuminifissa_ are considered by Zeiller[1524] to be portions of an _Archaeopteris_ or _Rhacopteris_ frond. The resemblance to the former genus is however by no means close enough to warrant a reference to _Archaeopteris_. The sterile specimens described by Stur[1525] from the Culm of Altendorf as species of _Archaeopteris_ are probably not generically identical with the Irish and Arctic species. The dichotomous branching of the rachis in _A. Tschermaki_ and _A. Dawsoni_ is a feature unknown in _Archaeopteris_. In the absence of fertile pinnae the separation of _Archaeopteris_ from _Rhacopteris_ is by no means easy.

A. _Archaeopteris hibernica._ Fertile pinna. Dublin Geological
Survey Museum. (Reduced. After Kidston.)
B. _A. hibernica._ Pinnule. (Slightly enlarged. After Carruthers.)
C. _A. hibernica._ Base of petiole. (Dublin Museum. After Kidston.)
D. _A. archetypus._ Base of petiole: Ellesmere Land. (After
Nathorst. ⅚ nat. size.)
E. _A. fissilis._ Sporangia. (Slightly enlarged. After
Schmalhausen.)
F. _A. fissilis._ Sterile pinnule. Ellesmere Land. (Slightly
enlarged. After Nathorst.)
G. _A. fimbriata._ Bear Island. (After Nathorst. ⅚ nat. size.)
H. _Archaeopteris sp._ Ellesmere Land. (After Nathorst. ⅚ nat.
size.)]

_Archaeopteris_ was regarded by Carruthers as a fern closely allied to recent species of Hymenophyllaceae, but this conclusion was based upon an interpretation of the fertile segments which Kidston[1526] has shown to be incorrect. The latter author regarded the presence of stipules and the structure of the exannulate sporangia as evidence of a Marattiaceous alliance. In a later reference to _Archaeopteris_, Kidston expresses the opinion that the genus is not a true fern but a member of the Cycadofilices or Pteridosperms, a view shared by Grand’Eury[1527] and doubtless by many other palaeobotanists. The sporangia of _Archaeopteris_ appear to be of the same type as those of _Dactylotheca_ (fig. 290, E, p. 399). Schmalhausen gave expression to his disagreement with Nathorst and other authors who referred _Archaeopteris_ to the Marattiaceae by proposing the distinctive group-name Archaeopterideae.

There can be little doubt that the reproductive organs of _Archaeopteris_ so far discovered are microsporangia, and that the plant bore seeds. The sporangia are larger than those of any known fern and, as Kidston points out, they are similar to those of _Crossotheca_ which he has shown to be microsporangia of the Pteridosperm _Lyginodendron_. The presence of stipules in _Archaeopteris hibernica_, _A. fimbriata_, _A. archetypus_ (fig. 369, D) and probably throughout the genus does not materially affect the question of taxonomic position. Stipules are a characteristic feature of Marattiaceae and, in a reduced form, of Osmundaceae, but similar appendages are borne at the base of the petiole of the Cycad _Ceratozamia_. The occurrence of Aphlebiae on the rachis of _Archaeopteris_ is a feature shared by the fronds of _Neuropteris_ and other Pteridosperms.

Neuropteris.

The fronds for which Brongniart[1528] created this genus, though suspected by Stur in 1883 as wrongly classed among the ferns, have only recently been shown to be the leaves of Pteridosperms. As yet only one case is recorded in which

_Neuropteris_ pinnae occur in organic connexion with seeds[1529], but it is almost certain that the genus as a whole must be placed in this generalised group. Renault[1530] pointed out that the petioles of Neuropteris fronds from Autun had the anatomical features of _Myeloxylon_ (petiole of _Medullosa_). Since Kidston’s important discovery of seed-bearing pinnae of _N. heterophylla_, Grand’Eury[1531] has recorded the association of Neuropteris fronds with seeds in French Coal-fields. By some of the older authors _Neuropteris_ was compared with _Osmunda_ because of a similarity in venation. In the frequent dichotomy of the frond and in the occurrence of pinnules on the rachis, _Neuropteris_ closely resembles _Odontopteris_[1532]: there can be little doubt as to the close relationship of the Pteridosperms possessing these two types of foliage. _Neuropteris_ may be defined as follows:

Fronds reaching a considerable size, probably in soma cases a
length of 10 metres[1533]; bi- or tri-pinnate; the rachis may be
dichotomously branched (figs. 354, D; 370); both rachis and petiole
bear single pinnules, those on the latter frequently differ from
the normal leaflets in their larger Cyclopteroid laminae (fig.
370). Pinnules entire, rarely slightly lobed, broadly linear,
attached by a small portion of the base, which is usually more or
less cordate. In _N. Grangeri_ Brongn. the pinnules are attached by
a short pedicel[1534]. The midrib always dies out before reaching
the blunt or pointed apex of the lamina and gives off at an acute
angle numerous secondary veins characterised by their arched course
and repeated forking.

Potonié describes the secondary veins of the pinnules of _Neuropteris pseudogigantea_[1535] as occasionally anastomosing, a feature which may be regarded as a step towards the reticulate venation of the closely allied genus _Linopteris_.

Renault[1536] described some petrified pinnules of _Neuropteris_ in which the mesophyll shows a differentiation into upper palisade tissue and lacunar tissue below; the lower epidermis is infolded at intervals where grooves (probably stomatal) occur like those on the leaves of an Oleander (_Nerium oleander_).

The rachises of Neuropteris fronds are described by Grand’Eury under the generic name _Aulacopteris_[1537].

_Neuropteris heterophylla_, Brongniart[1538]. Figs. 354, E; 371.

This species is characteristic of the Lower Coal-Measures of Britain; it occurs also in the Middle Coal-Measures and is a common type in Upper Carboniferous rocks in various parts of the world. The fronds are large and tripinnate, the rachis is often dichotomously branched and Cyclopteroid pinnules may occur on the petiole. The pinnules, 5–20 mm. in length and 3–8 mm. broad, have a rounded apex (fig. 354, E, p. 535).

As shown in fig. 371 which represents a primary pinna, the small pinnules on the lower branches are gradually replaced in the upper portion of the specimen by falcate segments.

_Neuropteris macrophylla_, Brongniart[1539]. Figs. 354, D, D′; 372.

The rachis of the large fronds of this species illustrates the dichotomous habit of many Neuropteris fronds, also the occurrence on the petiole of large Cyclopteroid pinnules (cf. fig. 370). The small piece of a pinna reproduced in fig. 372 shows the slender attachment of the segments, the blunt apex, and the Neuropteroid venation. Single pinnules of this species may be distinguished from those of _N. Scheuchzeri_ by the blunter apex, the absence of the pair of small Cyclopteroid pinnules on the same branch and by the absence of hairs. _N. macrophylla_ is characteristic of the Upper Coal-Measures of Britain.

_Neuropteris Scheuchzeri_, Hoffmann. Figs. 354, F; 373.

Fragments of this well-known Coal-Measure species were figured by Scheuchzer in his _Herbarium Diluvianum_[1540] as _Lithosmunda minor_, and by Lhywd (Luidius[1541]) as _Phyllites mineralis_ as early as 1760. _Neuropteris Scheuchzeri_, so named by Hoffmann in 1826, is a type which many authors have described under different names. Lesquereux[1542] figured it as _N. hirsuta_ from the Coal-fields of Pennsylvania, and under the same name it is recorded by Fontaine and White[1543] from Permian rocks of Virginia. The oval patches on the surface of a pinnule described by these authors as sori are certainly not of that nature. The same species is described by Bunbury[1544] from Nova Scotia as _N. cordata_ Brongn. var. _angustifolia_. For a full synonymy of the species reference should be made to lists published by Kidston[1545], White[1546], and Zeiller[1547].

The large tripinnate fronds are characterised by the long linear- or oval-lanceolate pinnules (fig. 373)[1548] with a pointed apex and numerous bristle-like hairs on the lamina; two much smaller Cyclopteroid segments occur at the base of the pinnae which are terminated by the linear leaflets (fig. 354, F, p. 535).

_Neuropteris Scheuchzeri_ is characteristic of the Upper and Middle Coal-Measures of Britain and is recorded from several localities in North America and the Continent. Zalessky[1549] has recently recorded the species from the Coal-Measures of Donetz. The frequent occurrence of detached pinnules points to a caducous habit. Even single leaflets can, however, be identified by their large size, the pointed apex, and hairy lamina. The hairs are preserved as fine oblique lines simulating veins; they were so described by Roemer[1550] who took them for cross-connexions between the secondary veins and referred the pinnules to Gutbier’s genus _Dictyopteris_.

Another example of _Neuropteris_ with hairy pinnules is described from the Commentry Coal-field by Renault and Zeiller as _N. horrida_[1551]. The oval-linear, bluntly rounded, pinnules are characterised by a median band of hairs on each surface and a narrower strip at the edge of the lamina.

Cyclopteris.

This generic name was created by Brongniart in 1828[1552] for specimens which he believed to be complete single leaves of orbicular or reniform shape similar to those of _Trichomanes reniforme_. The lamina is traversed by numerous dichotomously branched veins which spread from the centre of the base.