SELLARDS: NEW GENUS OF FERNS. 181 



"herbaceous ferns. The large fronds now at hand, having a 

 strong rachis broken off short at the base, make it more proba- 

 ble that the fronds are detached from the upright, more or less 

 arborescent stem. It seems even possible, but not probable, 

 that w^e have here only the ultimate division of larger fronds. 



Generic relation. — Among Paleozoic plants, the genus most 

 closely related to ours in the form and development of the frond 

 is Protoblechnum Lesqx. The type, and only species known of 

 this genus, comes from near the base of the Coal Measures, 

 Rushville, Ohio, and was first described as Althopteris holdeni by 

 Andrews.* Lesquereux afterward made Andrews's species the 

 type of the genus Protoblechnum Lesqx, P. holdeni (And.) Lesqx. 

 has, like the species of Glenopteris, sessile, auricled pinnules, 

 reduced at the base of the petiolate frond. The estimated 

 length of this species, 50 to 60 cm., is only slightly larger 

 than that of the largest species of Glenopteris. The apical part 

 of the frond of Protohlechninn differs, however, entirely from that 

 our genus. In the several species of Glenopteris the pinnules 

 are reduced gradually towards the apex of the frond, at last 

 uniting with a terminal pinnule. The frond of Protoblechnum is 

 represented as ending abruptly, the pinnules not at all reduced. 

 It might be suspected that the apex of the specimen was gone, 

 especially as the rachis continues moderately strong to the very 

 last, were it not that both authors agree in describing the frond 

 as complete. Lesquereux says (Coal Flora, p. 188) : "The 

 upper ones (pinnules) are close, less distinctly scythe-shaped, 

 but quite as long, the terminal leaflets being still 6 cm, long," 

 The venation of Protoblechnum Lesqx. is apparently distinct, the 

 veins twice forked ; the venation of Glenopteris is indistinct, 

 and often obliterated, the veins simple or forked once. The 

 thick coating of scales on the rachis of Protoblechnum is a minor 

 character not seen on any species of Glenopteris. 



Glenopteris cannot be closely compared with any other genus 

 of Carboniferous ferns. It has, however, in the sessile decur- 

 rent pinnules, a general relation to all the genera of the alethop- 

 teroid group, to wdiich it accordingly finds its most natural 

 reference. The relation after Protoblechnum Lesqx. is perhaps 

 closest to Alethopteris St. But the genus differs from all the 

 other Alethopterids again excepting Protoblechnum, in the sim- 



*Geol. Survey of Ohio Pal., vol. 2, p. 420, pi. LI, figs. l-2a. 

 13-K.U.Qr. A— ix3 



