728 MR W. T. GORDON ON 



1896. Rachiopteris esnostensis, B. Renault, "Bass, houil, et perm. d'Autun et d'Epinac" (pi. xxx. fig. 5 a 8). 

 1896. Diplolahis forensis, B. Renault, "Bass, houil. ct perm. d'Autun et d'Epinac" (fig. 6 a 10, 

 pp. 14 e^l 5). 



1908. Flicheia esnostensis, F. Pelourde, "Observations sur un nouveau type de Petiole fossile le Flicheia 



esnostensis, nov. gen., n. sp.," Memoires de la Societe d'Histoire naturelle d'Aidun, xxi. 



1909. Zygopteris petty cur ensis, Gordon, Report British Association, Winnipeg, 1910. 



Localities. Devonian of Falkenberg, Culm of Autun, and Calciferous Sandstone of 

 Pettycur, Fife. 



Diagnosis. 



Stem long, frequently branched, the xylem strand consisting of two kinds of 

 tracheides. Inner tracheides short, square-ended, reticulately thickened and arranged 

 more or less in vertical rows. Outer tracheides long, pointed, reticulately thickened, 

 rather larger than the inner tracheides. No xylem parenchyma present. Xylem strand 

 circular in transverse section and from 3 to 5 mm. in diameter. Inner xylem 1*5 to 

 3 mm. diameter. Protoxylem groups of scalariform tracheides probably belong to the 

 decurrent petioles and not to the stem itself. They are seen either between the inner 

 and outer xylem, or passing through the outer xylem. Cortex of stem without scleren- 

 chyma. Root-traces very large, barrel-shaped, diarch. 



Petiole-trace at first elliptical but gradually becoming H or X-shaped ; the arms 

 inclined at a high angle to the cross-bar of the H. Protoxylem groups, of scalariform 

 tracheides, situated one near the apex of each arm, in a sinus. Tracheides of petiole- 

 trace reticulately thickened. Ends of the arms dilated. Pinnae in four orthostichies. 

 Pinna-traces inserted on the arms of the petiole-trace in pairs. Each pair unites to 

 form a bar of xylem before it joins the arms. Two small aphlebia-traces, one on each 

 side, join the pair of pinna-traces. The four fused strands constitute an arc or bar of 

 xylem which closes over the ends of the two arms. The bar encloses with the two arms 

 a large triangular island of parenchyma. Trace of the pinna horseshoe-shaped, and not 

 unlike that of Mef.aclepsydropsis duplex. Secondary pinna-traces tend to assume the 

 same shape as the primary ones. 



Aphlebia-traces branch once, one branch passing out at a higher level than the other. 



Sporangia and foliage unknown. 



Conclusions and General Considerations. 



From the characteristic form ultimately assumed by the petiole-traces which arise 

 from the stem described above, there can be no doubt that the stem is that of a 

 Diplolabis. The petiole to which this generic name was applied has now been 

 recorded from three localities, from the Devonian rocks of Falkenberg, from the Culm 

 measures of Autun, and from the Calciferous Sandstone Series of Pettycur, Fife. 

 Among the specimens from these localities no characters can be found sufficiently 

 distinct to discriminate the petioles specifically. Even D. forensis (Renault) cannot be 



