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.)

Schenk[870], who described several specimens of Laccopteris from Rhaetic rocks of Germany, compared the genus with Gleichenia but he also recognised the close resemblance to Matonia pectinata. Zeiller[871] first established the practical identity of the sori and sporangia of Laccopteris and Matonia. The Rhaetic species, such as L. Muensteri, L. elegans, and L. Goepperti, agree very closely with L. polypodioides and need not be described in detail.

Fig. 264. Laccopteris elegans (Presl). (From a specimen in the British Museum; from the Lower Keuper of Bayreuth, Germany. Nat. size; part of pinnule × 3.)

The Rhaetic species Laccopteris elegans, represented in [fig. 264], illustrates the characteristic habit of the genus and shows a feature usually overlooked[872], namely the occurrence of anastomoses between the lateral veins. The form of the sorus of another Rhaetic species is shown in [fig. 265], E. Schenk figures an interesting series of fronds of L. Goepperti in different stages of growth[873]; one of the younger leaves is seen in [fig. 265], D. An examination of Rhaetic specimens of Laccopteris in the Bergakademie of Berlin convinced me of the correctness of the published descriptions of the sori.

Fig. 265.

  1. Matonidium Wiesneri. (Slightly enlarged.)
  2. Marattiopsis marantacea. (Slightly enlarged.)
  3. Gleichenites gracilis. (Slightly enlarged.)
  4. Laccopteris Goepperti. (Slightly reduced.)
  5. L. Muensteri. (Enlarged.)

(A, after Krasser; B, C, after Leuthardt; D, E, after Schenk.)

Laccopteris polypodioides (Brongniart). Figs. [266–268]; [278], A.
1828.Phlebopteris polypodioides[874], Brongniart, Hist. vég. foss. p. 372, Pl. LXXXIII. fig. 1.
—P. propinqua, ibid. Pls. CXXXII. fig. 1, CXXXIII. fig. 2.
1829.Pecopteris caespitosa, Phillips, Geol. Yorks. p. 148, Pl. VIII. fig. 10.
—P. crenifolia, ibid. Pl. VIII. fig. 10.
—P. ligata, ibid. Pl. VIII. fig. 14.

Fig. 266. Laccopteris polypodioides (Brongn.). (× 14.) (Brit. Mus.)

In habit this species closely resembles Matonia and Matonidium, the long petiole divides distally into several spreading pinnatifid pinnae with linear ultimate segments ([fig. 278], A). Circular sori (indusiate?) occur in a single row on each side of the midrib containing 12–14 large sporangia ([fig. 266]) characterised by an obliquely vertical annulus. The midrib of the pinnules gives off secondary veins at a wide angle and these form a series of elongated meshes parallel to the median rib, as in the recent genus Woodwardia; forked and anastomosing branches are given off from these to the edge of the lamina ([fig. 267]).

Fig. 267. Pinnules of Laccopteris. (Enlarged.)

The specimen shown in [fig. 268] is probably a young frond of this species.

A very similar, possibly a specifically identical plant, was described by Leckenby from English Jurassic rocks as Phlebopteris Woodwardi[875], the distinguishing features of which are the greater number of lateral veins and the smaller sori ([fig. 267], A).

The name Microdictyon was proposed by Saporta[876] for pinnules differing slightly from those of Laccopteris in venation characters: he included Laccopteris Woodwardi in this genus, but such differences as are recognisable in the venation hardly justify the use of a distinct generic title. Similarly, specimens described by Debey and Ettingshausen[877] from Lower Cretaceous rocks of Aix-la-Chapelle as species of Carolopteris may also be included in Laccopteris.

Fig. 268. ? Laccopteris polypodioides. Nat. size. From a specimen in the Whitby Museum (Brit. Mus.).

Laccopteris Dunkeri (Schenk)[878].

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.

Fig. 269. Matonidium Goepperti (Ettings.). (A, B, ½ nat. size; C, approximately nat. size.)

Fronds pedate and apparently identical in habit with those of Matonia pectinata; ultimate segments linear, slightly falcate and bluntly pointed. Sori circular or oval, numerous, containing 15 to 20 sporangia with an oblique annulus, in two rows on the lower surface of the pinnules; indusium as in Matonia.

The English examples have so far afforded no information in regard to sporangial structure, but Schenk[883] has recognised a distinct annulus in German material. In his description of fossil plants from Lower Cretaceous rocks in California, Fontaine[884] doubtfully identifies two very small fragments as Matonidium Althausii; the evidence is, however, wholly inadequate.

Matonidium Wiesneri, Krasser[885]. [Fig. 265], A.

This Cenomanian (Cretaceous) species from Moravia appears to be identical in habit with the older type. The pinnules are larger and bear fewer sori. Krasser’s figures of the sterile pinnules show no lateral anastomosing between the secondary veins, but the small vascular network below each sorus ([fig. 265], A) is identical with that in Matonia pectinata. The indusiate sori contain about six sporangia with an oblique annulus.

The very wide geographical distribution of the Matonineae during the Mesozoic era affords a striking contrast to the limited range of the Malayan survivals.