Sagenopteris.

This generic name was applied by Presl[1225] to small fronds composed of four or rarely two palmately disposed leaflets with a more or less distinct midrib and anastomosing secondary veins. Schimper[1226] compared Sagenopteris with Marsilia, but did not regard the resemblance as evidence of relationship. Nathorst[1227] expressed the opinion that certain fruit-like bodies obtained from the Rhaetic beds of Scania are of the nature of sporocarps and were borne by Sagenopteris, with the leaves of which they were associated. He published a drawing of part of a fruit showing on its partially flattened surface some raised oval bodies which are considered to be spores. Dr Nathorst kindly placed at my disposal the drawings reproduced in [fig. 325] made from some of his specimens found at Bjuf in Scania.

In contour and superficial features, e.g. the veining on the wall, these bodies bear a fairly close resemblance to the sporocarps of recent species of Marsilia. They were found in association with the leaves of Sagenopteris undulata Nath., an abundant Scania type similar in form to the English Jurassic species S. Phillipsi (figs. [327], [328]). Heer was independently led by an examination of some examples of the Swedish “fruits” to compare them with the sporocarps of Marsilia. A small spherical body is figured by Zigno[1228] close to a leaf of his species S. angustifolia, which may be a sporocarp. In a recent paper, Salfeld[1229] says that he found fructification on the lower face of the leaflets of S. Nilssoniana Brongn. from German Jurassic rocks, but he brings forward no evidence in support of this statement. The systematic position of Sagenopteris is by no means settled. In a previous account of the genus I expressed the view that it is probably a member of the true ferns[1230], but the resemblance of Dr Nathorst’s drawings to the Marsilian sporocarps influences me in favour of his opinion that Sagenopteris may belong to the Hydropterideae. The evidence, as Solms-Laubach[1231] states, is not wholly satisfactory: Schenk points out that the frequent occurrence of detached Sagenopteris leaflets suggests that they easily fell off the petiole, whereas in Marsilia the leaflets do not fall off independently. The discovery of a new type of Marsiliaceae in Brazil, which Lindman has described as Regnellidium diphyllum[1232] ([fig. 326], A), affords an additional piece of evidence bearing on the comparison of Sagenopteris with members of this family. In Regnellidium the leaves differ from those of Marsilia in bearing two instead of four leaflets, and in the former the veins are repeatedly forked, and do not anastomose as in Marsilia. In the possession of only two leaflets Regnellidium agrees with some forms of Sagenopteris ([fig. 328]).

Fig. 325. Sporocarp-like bodies found in association with the leaves of Sagenopteris. (Nat. size. From drawings supplied by Dr Nathorst.)

Fig. 326.

Regnellidium diphyllum Lind. Single leaf and stalked sporocarp. (⅞ nat. size. After Lindman.)
Cuticle of Sagenopteris rhoifolia. (After Schenk.)

Sagenopteris Phillipsi (Brongniart)[1233]. Figs. [327], [328].

1828.	Glossopteris Phillipsi, Brongniart, Hist. vég. foss. p. 225, Pls. LXI. bis, LXIII.
1838.	Sagenopteris Phillipsi, Presl, in Sternberg’s Flor. Vorwelt, vii. p. 69.

Fig. 327. Sagenopteris Phillipsi.

From the type-specimens of Lindley and Hutton (Glossopteris Phillipsi). Gristhorpe Bay, Yorkshire. British Museum, No. 39221. Slightly reduced. M.S.
From a specimen in the British Museum (39222). Nat. size. Figured by Lindley and Hutton as Glossopteris Phillipsi.

The fronds of this common Jurassic species, which is recorded from many European localities, from North America, Australia, the Antarctic regions[1234], and elsewhere, are very variable as regards the form, size, and number of the leaflets.

Frond petiolate, in some forms the petiole bears four linear or oval-lanceolate leaflets having a distinct midrib and oblique anastomosing veins. In others a shorter winged petiole bears one or two shorter and broader, somewhat obcuneate, leaflets without a midrib.

It is probable that Bunbury[1235] was correct in his opinion that the specimen figured by Lindley and Hutton[1236] as Otopteris cuneata, characterised by two leaflets ([fig. 328]), is not specifically distinct from the normal form with four leaflets ([fig. 327]).

Similarly, such specimens as that represented in Pl. XVIII., fig. 3 of the first part of my Jurassic Flora, in which a short stalk bears only one leaflet may, provisionally at least, be included in Brongniart’s species. Yabe[1237] describes a form with two leaflets from Jurassic rocks of Korea as Sagenopteris bilobata which resembles S. Phillipsi; and Moeller[1238] records a specimen similar to that represented in [fig. 328] from Bornholm as S. cuneata (Lind. and Hutt.).

Fig. 328. Sagenopteris Phillipsi. From a specimen in the Manchester University Museum. Nat. size.

The leaf shown in [fig. 327], A, in which the longest segments are 4·5 cm. in length, represents the most abundant form and illustrates the very close agreement between S. Phillipsi and the Rhaetic species S. rhoifolia. Fig. 327, B, which is drawn from a specimen figured by Lindley and Hutton[1239], shows a leaf with longer (6·5 cm.) and much narrower segments. Broader leaflets are occasionally met with in which the lamina reaches a length of 11 cm.[1240]

Leaves with leaflets narrower (3 mm. broad) than those represented in [fig. 327], B, are described by Zigno[1241] from Jurassic beds of Italy as S. angustifolia and by Moeller[1242] from the Jurassic of Bornholm as S. Phillipsi f. pusilla. A coarser type of venation than that of S. Phillipsi is occasionally found in Jurassic examples, as in S. grandifolia Font.[1243] from Oregon and S. Nathorsti Barth. from Bornholm[1244].

•••••

Sagenopteris is recorded also from several Rhaetic floras. The best known species, S. rhoifolia Presl[1245], is hardly distinguishable from some forms of S. Phillipsi or from the Italian Jurassic species described by Zigno as S. Goeppertiana[1246], though the leaflets are usually rather larger. This species was first described by Brongniart as Filicites Nilssoniana[1247], and a few authors[1248] have adopted this specific name because of its priority over Presl’s designation. As Nathorst remarks, to give up the well-known name S. rhoifolia for S. Nilssoniana is “mere pedantry.” The epidermis of S. rhoifolia as figured by Schenk[1249] consists of cells with straight and not undulating walls: stomata occur on the lower surface ([fig. 326], B).

Rhaetic leaves of the type represented by S. rhoifolia have a wide geographical distribution.

The specimens described by Feistmantel from the Damuda series of India as Sagenopteris longifolia are no doubt fronds of Glossopteris longifolia[1250].

The Wealden species Sagenopteris Mantelli (Dunk.)[1251] agrees closely in habit and in the form of the leaflets with S. Phillipsi and S. rhoifolia. It is probable that some of the leaves described by Velenovský[1252] from Lower Cretaceous rocks in Bohemia as Thinnfeldia variabilis are portions of Sagenopteris fronds. S. Mantelli is recorded from several European localities, from California[1253], and elsewhere.

Sagenopteris appears to have been widely distributed during the Rhaetic, Jurassic and Lower Cretaceous floras. The very great similarity between the specimens recorded from these three formations renders the genus an uncertain guide in regard to geological age. Decisive evidence as to its position in the plant kingdom is at present lacking: the inclusion of the genus as a possible member of the Hydropterideae has still to be justified.