380 DR. D. H. SCOTT ON BOTRYCHIOXYLON PARADOXUM. 
of doubt. Open sinuses (closed only at the emission of a lateral strand) are character- 
istic of Dineuron ; but we cannot refer our petiole to that genus, for in the upper of the 
two sections (2465) there are fairly well-marked antenne, the terminal regions of the 
xylem being much broader than the median band (PI. 41. fig. 24). 
The phloem is preserved, but not well defined. It is best shown in the lower section 
(see Pl. 41. fig. 23); in the parts bordering on the median band it is a large-celled tissue. 
A definite layer bounding the whole bundle in this section may possibly be the 
endodermis, and the tissue immediately within it the pericycle; in the upper section 
these regions are very ill defined (Pl. 41. fig. 24). 
It would be a great help in determining the relationships of the petiole if the secondary 
rachis-bundles were present; there are some obscure indications in the cortex of the 
petiole which may be of this nature, but the preservation is too bad for anything to be 
made of them. 
As the evidence is against the presence of a “ filament," the sinuses thus being open 
and not forming peripheral loops, we cannot place our plant in the genus Ankyropleris: 
the same consideration excludes the genera Clepsydropsis and Asterochlena. We have 
seen that the form of the petiolar bundle forbids a reference to Dineuron; there are no 
grounds for a comparison with the restricted genus Zygopteris*. 
The only genera of Zygopteridese which can be taken into consideration are Etapteris, 
Diplolabis, and Metaclepsydropsis. We know nothing of the stem of Htapteris or of 
the basal region of the petiole. There is a slight sinus at each end of the xylem, 
between the protoxylem groups (P. Bertrand, ’09, fig. 20, p. 142, and ’11, fig. 3, p. 26), 
and it is conceivable that at the base of the petiole, where the whole structure would no 
doubt be more condensed, the bundle might resemble that in Botrychioaylon. This, 
however, is merely conjectural. A petiole of Htapteris Scottió is associated with the 
Botrychiorylon, but the petiole and rachis of an Ankyropteris are also present, and no 
conclusion can be drawn. Both in Diplolabis and Metaclepsydropsis the sinuses of the 
petiolar xylem are open. Dr. Gordon in his memoir on Diplolabis Rémeri (Gordon, 11) 
has demonstrated the remarkable changes which the leaf-trace passes through in its 
course. Atalow level there is some resemblance to the Botrychioxylon bundle (Gordon, 
‘11, pl. 2. fig. 25), though not an exact one. The analogy is of some interest, though 
the stem-structure precludes any very close affinity. 
As regards Metaclepsydropsis, also thoroughly investigated by Dr. Gordon (’11°), what 
has been said of Dinewron may be repeated, for at low levels the Metaclepsydropsis trace 
has almost exactly Dineuron structure (Gordon, '112, p. 171, pl. 2. fig. 24, &c.). At no 
level bas the bundle of Metaclepsydropsis any prominent antennze such as we find in the 
upper section of our petiole (P1. 39. fig. 13 and Pl. 41. fig. 24). Still, there is à general 
resemblance, especially in the lower part of the petiole (Gordon, ’11’, pl. 2. figs. 19-22), 
and taking the stem-structure into account it appears that the two genera are somewhat 
nearly allied. 
On present evidence, the petiolar structure of Botrychioxylon does not agree with 
* For these genera see P. Bertrand, '09 and '11. 
