Salmi.—On the Branching of the Zygopteridean Leaf. 375 
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important and far-reaching distinction is based upon the biseriate or 
quadriseriate arrangement of the (free) branch-axes of the leaf. In the 
quadriseriate forms the free branches are, as we have seen, tertiary raches 
formed by the terminal forking of the adnate secondary raches ; in the bi¬ 
seriate forms the secondary raches themselves are free, and do not fork. 
This distinction is associated with important differences in the mode of 
branching of the vascular strands. 
However, if there is any foundation for the suggestion that Gyropteris 
sinuosa is the free secondary rachis of a form like Metaclepsydropsis duplex ox 
Diplolabis ) a classification mainly based on the external characters would no 
longer be tenable. In any case it seems preferable to rely more upon the 
vascular structures. 
The most recent scheme of phylogeny ( 2 ) is the combined result of the 
work of Dr. Gordon and Dr. Bertrand. In attempting to elucidate the 
closer relations of the genus Stauropteris, the latter author concludes 
that of all the Zygopteriaeae the closest resemblance is that with Anky- 
ropteris bibractensis , var. westphaliensis , P. Bertr. ( 1909 , p. 164). The 
different parts of the two leaf-traces are closely compared, and the 
‘ filament ’ of Ankyropteris is represented as being fused indistinguishably to 
the side of the Stauropterid leaf-trace (see Fig. 34, p. 169). In face of the 
clear resemblances with Diplolabis and similar forms it is very doubtful that 
the comparison instituted by Dr. Bertrand is admissible. Stauropteris , like 
Diplolabis , has two planes of symmetry in the leaf-trace; the pinna-trace 
arises in both genera by the meeting of two processes, and in both genera it 
at once dichotomizes. In all these respects the leaf-trace of Ankyropteris 
westphaliensis is different: it has only one plane of symmetry ; the pinna- 
trace arises as a closed ring, and in a manner which even for that genus is 
peculiar to this species ; moreover, the pinna-trace does not fork. 
In 1915 Mrs. E. M. Osborn ( 11 ) briefly described an important fossil 
from New South Wales, which, while possessing the Ankyropteris Grayi 
type of cauline stele, had leaf-traces similar to those of Clepsydropsis antiqua , 
Unger. The origin of the leaf-trace resembles that known for A. corrugata 
and—except for the absence of axillary branches—for A. Grayi. A short 
account of a similar but incomplete fossil, from a different locality in New 
South Wales, was read before the Cambridge Philosophical Society on 
February 19, 1917, and the full paper will appear in a future' number 
of the ‘ Annals’. I have since learnt from Mrs. Osborn that the two plants 
are specifically identical. 
I have no doubt that the stem-structure and leaf-trace origin in Clepsy¬ 
dropsis antiqua and C. kirgisica was essentially similar to that in the 
Australian fossil, and that the two genera Clepsydropsis and Ankyropteris 
should be united. 1 In view of this I had at first included the former genus 
1 A more complete discussion of this question is given in my forthcoming paper. 
