4 HALLE, ON THE SWEDISH SPECIES OF SAGENOPTERIS PRESL AND ON HYDROPTERANGIUM NOV. GEN. 



Swedish species of Sagenopteris Presl. 

 Sagenopteris undulata Nath. 



(Pl. 1, figs. 1—15; pl. 3, figs. 1 — 5.) 



1878. Sagenopteris undulata Nathorst (4). P. 26; pl. 2, figs. 2 — 4. 



1878. Sagenopteris dentata, pro parte, Nathorst (4). P. 27; pl. 2, fig. 5. 



1878. Sagenopteris rhoifolia Pkesl? Nathorst (4). P. 27; pl. 1, fig. 17; pl. 8, fig. 2. (Conf. Nathorst 1886, 



p. 121.) 



1878. Sagenopteris undulata Nathorst (3). P. 11; pl. 2, fig. 3. 



1886. Sagenopteris ulata Nathorst (6). P. 85, 121; pl. 1, fig. 17; pl. 19, fig. 4. 



1886. Sagenopteris undulata Nathorst (6). P. 85, 121; pl. 19, figs. 2, 3. 



The chief character of this species is the undulating or dentate margin of the 

 pinna? of the full-grown leaves. 



The pinnse are normally four in number, attached to the summit of a common 

 petiole, which is often of great length — as long as the pinnae or longer. The pinna? 

 are lanceolate or linear, generally with a long, gradually tapering apex. The midrib 

 is, in most cases, distinct through the whole lamina; sometimes it is not at all devel- 

 oped. The lateral veins are slightly arched, forming meshes of medium size (pl. 1, 

 fig. 13). The margin of the smaller pinna? is often entire (pl. 1, figs. 10 — 14). In 

 fully developed leaves the outline of the pinnse is undulating or irregularly dentate. 

 Fig. 1, pl. 1 represents a typical full-grown leaf with dentate pinnse. That the ex- 

 treme forms only represent varieties of one species is evident from the common 

 occurrence of transitional stages. The small specimens with an entire margin of the 

 pinnae may perhaps represent imperfectly developed leaves or such belonging to 

 young plants. 



In his monograph of the fossil flora of Bjuf (6, p. 85; pl. 1, fig. 17; pl. 19, 

 fig. 4) Prof. Nathorst has described a new species, Sagenopteris alata, distinguished 

 by its small size and very broad winged petiole. He remarks, however, that the few 

 specimens attributed to this species may be young leaves of 8. undulata, and also 

 draws attention to the occurrence in the recent genus Marsilia of differently shaped 

 primitive leaves, with a broad, slightly winged petiole. In consequence of the exist- 

 ence of various transitional forms I have adopted the latter view and classed 8. 

 alata as a variety of S. undulata. On pl. 1 I have figured some typical specimens 

 of 8. alata (figs. 4 — 6). Figs. 8 — 10 show three intermediate forms with narrower 

 petioles than those of S. alata, yet broader than in typical S. undulata. The broad 

 petiole of the 8. alata-forms has almost the aspect of a real lamina, being comparat- 

 ively thin in texture. The midrib is however very broad, and no lateral veins have 

 been observed. The petiole seems to have been attached to the stem with a broad 

 base. 



In fully developed leaves of 8. undulata the mode in which the pinna? are 

 borne by the petiole, varies considerably. In some specimens they are attached in 

 one point directly to the summit of the petiole. In this case there is an obvious 



