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].
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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).