Kids ton.—Note on the Petiole of Zygopteris Grayi, Will. 455 
* axillary shoot which I believe is morphologically a branch which gives 
rise to, but which does not of its own tissue contribute to, the formation of 
the leaf-trace. 
It may be further pointed out that Zygopteris Grayi is by no means 
the most primitive type of Zygopteris. In Zygopteris corrngata , according 
to Dr. Scott, there is no ‘ axillary shoot * in connexion with the leaf depar¬ 
ture, and in the older Zygopteris (Diplolabis) Roemeri , Solms, from the 
culm, of which the stem was recently described by Mr. W. T. Gordon before 
the Royal Society of Edinburgh, 1 the petioles arise directly from the solid 
protostele, and their steles assume the characteristic Zygopteroid form in 
their passage through the cortex. 
The presence of a small stem from which the petioles arise, and the 
occurrence of a mixed pith in Zygopteris Grayi , would indicate that it has 
travelled some considerable distance from the primitive type of Zygopteroid 
structure. 2 
1 Dec. 20, 1909. 
2 Note. — Zygopteris ( Ankyropteris ) scandens , Stenzel (Die Gattung Tubicaulis Cotta , p. 31, 
PI. VI, Figs. 50-5, PI. VII, Figs. 56-65, 1889),has been considered by some botanists as synonymous 
with Z. Grayi, Will., but is essentially distinct from that plant and is easily distinguished by the form 
of its petiole trace. The cross-bar of Z. scandens is formed of two rows of much larger tracheae than 
those of Z. di-upsilon ( = Z. Grayi), where the cross-bar is seven or eight rows wide. The arms of 
Z. scandens are slightly incurved and do not possess the outward spreading form of those of Z. di- 
upsilon, but above all, the abaxial arms of Z. scandens bend inwards towards each other and are 
shorter than the adaxial arms. The bar is also slightly curved, which gives the leaf-trace an 
inequilateral form ; or, to put it in other words, the petiole trace of Z. scandens has only one plane 
of symmetry—the vertical, while that of Z. Grayi has two planes of symmetry—the vertical and 
horizontal. These two species cannot therefore be united. (See Stenzel, 1 . c., PI. VII, Fig. 63.) 
EXPLANATION OF PLATE XXXIV. 
Illustrating Dr. Kidston’s paper on Zygopteris Grayi, Williamson. 
[All figures are enlarged about 17 times.] 
The * indicates the position of the axis of the stem. 
Fig. 1. From specimen contained in the Collection of the Manchester Museum, No. R. 443. 
Loc. Oldham. Hor. Halifax Hard Bed. 
Fig. 2. From specimen contained in the Author's Collection, No. 308. Loc. Oldham. 
Fig. 3. From specimen contained in the Collection of the Manchester Museum, No. R. 443. 
Loc. Oldham. 
Fig. 4. From specimen contained in the Author’s Collection, No. 308. a', a", Bar of petiole. 
Loc. Oldham. 
Fig. 5. From specimen contained in the collection of the Manchester Museum, No. R. 441. 
a, Bar of petiole; b, Branch. Loc. Sunfield, Oldham. 
Fig. 6. From specimen contained in the Author’s Collection, No. 305. b, Branch. Loc. 
Sunfield, Oldham. 
My thanks are due to Professor Weiss, for kind permission to figure and describe the specimens 
contained in. the Collection of the Manchester Museum. 
