Note on the Petiole of Zygopteris Grayi, Will. 
BY 
R. KIDSTON, LL.D., F.R.S. 
With Plate XXXIV. 
U NTIL the publication of Dr. Paul Bertrand’s ‘Etudes sur la fronde 
des Zygopteridees ’ last year, in which he unites Zygopteris bibrac- 
tensis var. Westphalica , P. Bertrand, 1 with Zygopteris Grayi , Will, sp., as its 
petiole, 2 I was under the impression that it was common knowledge that 
Zygopteris di-upsilon , Will., was the petiole of that stem. 
On communicating with Dr. Scott on this subject, I find I have been 
mistaken in believing that this relationship between Zygopteris Grayi and 
Z. di-upsilon was generally known, and on his suggestion the present note 
is written. 
Although Zygopteris Grayi has been more or less fully described 
by several botanists, 3 there are certain points in connexion with the so- 
called ‘ axillary shoot ’ which appear still to await description, and as this 
is intimately connected with the leaf-trace, even at the risk of repetition it 
seems desirable to describe the relation of the petiole to the so-called 
‘ axillary shoot 5 and to follow the former until it is given off and free 
in the cortex. 
As the term ‘axillary shoot’ seems to me very misleading, I must 
anticipate, for reasons which will be subsequently stated, and substitute the 
term ‘ branch ’ for this structure in the following description. 
The stem-stele of Zygopteris Grayi is more or less distinctly stellate in 
transverse section, but the length of the five arms varies in prominence, 
1 The Zygopteris bibractensis of Williamson, but possibly not the Zygopteris bibractensis of 
Renault. Ann. des Sci. Nat., 5 e ser., Bot. vol. xii, p. 171, PI. IX, Figs. 17 and 18. 
2 P. Bertrand, Etudes sur la fronde des Zygopteridees, pp. 106, 107, 222. 
3 1889. Rachiopteris Grayi , Will., Mem. xv, Phil. Trans., vol. clxxx (1889), B., p. 156, PI. I, 
Figs. 1, 2, 3, 4 (? Fig. 5) ; PI. II, Fig. 5 A. 
1900. Zygopteris Grayi , Scott, Studies in Fossil Bot., 1st ed., p. 278, Figs. 97 and 98; 2nd ed., 
vol. i, p. 306, Figs. 115 and 116, 1908. 
1908. Zygopteris Grayi , Tansley, Evolution of the Filicinean Vascular System, p. 16, Fig. 6. 
1909. Ankyropteris Grayi, P. Bertrand, Etudes sur la fronde des Zygopteridees, p. 107, PI. XI, 
Fig. 78. 
1880. Rachiopteris di-upsilon , Mem. x, Phil. Trans., pp. 537-8, PI. XXI, Figs. 90 and 91. 
1909. Etapteris diupsilon, P. Bertrand, 1 . c., p. 148, PI. I, Fig. 6; PI. XVI, Fig. no. 
[Annals of Botany, Vol. XXIV. No. XCIV. April, 1910.] 
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