269 
Dr. P. Bertrand on Zygopterideee. 
It is strange that in describing the stem of Z. corrugatn the 
author makes no mention of the internal system of small tracheides, 
which was described and clearly figured by Williamson in 1877,' 
and has often been referred to since his time. This seems to he a 
curious example of our author’s comparative indifference to stem- 
characters, while he is so minutely accurate in everything that 
concerns the frond. 
Part III., on comparative anatomy and classification, begins 
with the well-known Burntisland fossil, Williamson’s Rachiopteris 
duplex, now frequently referred to as Zygopteris, but placed by the 
author in a new genus, Metaclepsy drop sis. There is here relatively 
little to add to the account given by Mr. Tansley, though of course 
the facts are now brought into line with Dr. Bertrand’s general 
theory. 
The Devonian fossil, Clepsydropsis autiqua, Unger, is of special 
interest, for it has the simplest petiolar structure in the group, and 
is hence regarded by the author as the starting-point for quite a 
number of lines of descent. The transverse section of the main 
foliar bundle is somewhat dumb-bell-shaped, with the protoxylem 
internal, lining an elliptical space near each end; a single series of 
branches is given off on either side of the rachis. 
The leaf-bundle of Asterochlcena (here treated as a distinct 
genus) only differs from that of Clepsydropsis in its symmetry, the 
section being convex outwards, while the branches are directed 
towards the lower (posterior) face of the frond—a unique case, 
according to the author. 
The following chapter deals with the two genera Diplolnbis and 
Zygopteris ; the latter genus is sadly shorn of its old array of 
species and reduced to the Z. primaria of Cotta, alone. It remains 
to be seen how far later authors will follow Dr. Bertrand in his new 
classification ; it appears to be true, however, that Z. primaria is 
more nearly allied by its foliar structure to Diplolnbis than to the 
other species formerly referred to Zygopteris itself. 
Chapter III., of this Part, is devoted to the highly organized 
genus Etapteris, another new creation, of which the well-known 
Z. Lacattei of Renault may serve as a type. The English form of 
Renault’s plant is made a new species under the name Etapteris 
Scotti. The genus is characterized, on the author’s view, by the 
great development of the “ pieces receptrices ” which form the bulk 
* Organisation of Fossil Plants of the Coal-measures. Part VIII. 
Phil. Trans. Royal Soc., Vol. 167, Pt. I., p. 214; Plate 6, 
Figs. 13 and 14. 
