34 PALiEONTOLOGICAL BOTANY. 



the Hymenophyllea}, and is consequently nearly related to 

 the equally famous Killarney fern, Trichomanes radicans. 



Mr. Carruthers states that the frond-stalk of this fern is 

 thick, of considerable length, and clothed with large scales, 

 Avhich form a dense coyering at the somewhat enlarged base. 

 The well-defined separation observed in several specimens 

 probably indicates that the frond-stalks were articulated to 

 the stem or freely separated from it, and some root-like 

 structures which occur on the slabs with the ferns may be 

 their creeping rhizomes. The pinn« are linear, obtuse, and 

 almost sessile. The i^innules are numerous, overlapping, of 

 an ovate or oblong- ovate form, somewhat cuneate below, and 

 with a decurrent base. The veins are very numerous, uni- 

 form, repeatedly dichotomous, and run out to the margin, 

 where they form a slight serration. Single pinnules rather 

 larger than those of the pinnae are placed over the free spaces 

 of the rachis, as was pointed out by Brongniart. Carruthers 

 has not met with any recent fern in which this occurs ; but it 

 has been observed in several fossil species, as in the allied 

 American Pala3opteris Halliana (Sch.), in Sphenopteris erosa 

 (Morris), and others. The pinnules are sometimes entirely, but 

 only partially fertile. The ovate-oblong sori are generally 

 single and two-lipped, the slit passing one-third of the way 

 down the sorus. The vein is continued as a free receptacle 

 in the centre of the cup or cyst, as in existing Hymenophyllea3, 

 in which it is included, not reaching beyond its entire i^ortion. 

 In some specimens the receptacle is broad or thick, indicating 

 the presence of something besides itself in the cup, and giving 

 the aj^pearance that would be produced if it were covered 

 with sporangia ; there is no indication on the outer surface 

 which might have been expected from the separate sporangia. 

 The compression of the specimens in the rock, which has 

 made the free receptacle appear like a vein on the wall of 

 the cup, together with the highly altered condition of the 

 rock in which the fossils are contained, accounts for the 



