66 Dr. W. C. Williamson on 



own plant. Owing to some differences in the dimensions 

 of the two forms, he was unable to conclude that they were 

 identical. The petioles of both examples being alike fur- 

 nished with the characteristic Zygopteroid vascular bundle, 

 I shall, for the present, continue to follow his example, and 

 recognise my form under the more definite type-name of 

 Zygopteris. The first specimen of this type which came 

 into my hands I published in Memoir VI., under Corda's 

 name of AnacJioropteris Decaisnii, its peculiar Zygopteroid 

 petiolar bundle not having been discovered at that time. 

 This, however, has now been done ; and since has given 

 the name of Zygopteris to a characteristic example of this 

 group of stems. I have elected to follow his example, and 

 to apply the same type-name to the entire Zygopteroid group. 



RACHIOPTERIS. Will. 



Z. BIBRACTIENSIS. Renault. 



Transverse. 



F. — p. 697, Fig. 49, C.N. 195. For more perfect specimens see C.N. 

 196A and 197. 



Longitudinal. 



F. p. 697, Fig. 50, C.N. 108. See also C.N. 1815. 



Isolated Clusters of Semi-Sclerous Cells, apparently corre- 

 sponding to Fig. 32h of Heterangium Grievii. 

 N.— p. 291, Fig. n,t,t,t. C.N. 1304. 



Vascular Bundles, passing outwards through the Cortex, 

 resembling those of d, flg. 1?z, in lyginodendron, and d, 

 Fig. 35m'm, in HeteRx\ngium Grievii. 

 N. — p. 290. Fig. iu',u.' C.N. 1302. Fig. 711,11, C.N. 1623. Fig. 811, u, 

 1302. 



Special Bundles, resembling D, Fig. 7, and X, Fig. 24, in Lygino- 

 dendron, and D, Fig. 36, in Heterangium Grievii. 



N.— p. 292, Fig. I2w, C.N., 1622, and Fig. I3eee\ Fig. I3,e,e,w, 

 C.N. 1619. 



Structure of Tracheids. 



N. — Barred, p. 293, Fig. 14, C.N. 1 301. 



Reticulate, p. 291, Fig. 9, 1628. . . 



Bordered Pits, p. 293, Fig. 16, C.N. 1621, _L and I 



