54 
A. G. Tansley. 
great deal. Certain impressions known as Schizopteris and 
SchizostncJiys, the former a large fleshy bipinnate frond, are 
probably the sterile and fertile leaves of Zygopteris, and Renault 
figures the flabellate leaflet or pinna of a frond of Botryopteris. 
The fronds were apparently often dimorphic, and the sporangia 
were sometimes, at least, borne terminally on ultimate branchlets 
of a frond with reduced lamina. These sporangial pedicels were 
often crowded and show signs of dichotomous branching. In 
Stauropteris oldhamia (a frond whose stem is unknown but which 
shows strong affinity to, though its sporangia do not exactly con¬ 
form w r ith those of Botryopteridege) the ultimate branchlets were 
in crowded tufts with terminal sporangia. Some species of 
Zygopteris have axillary branching, and the relation of the stele of 
the branch to that of the leaf-trace is exactly the same as in the 
Hymenophyllacege. 
The general structure of the vascular system of the Botryo¬ 
pteridege shows, as we have said, very considerable variety. The 
Schizgeacege, among modern ferns, have a great range of vas¬ 
cular structure, both in stem and petiole, but they are far surpassed 
by the Botryopteridege, the variety of whose petiolar structure is in 
fact one of their most striking peculiarities, quite unparalleled in 
modern ferns. The stem-structure, though by no means uniform, 
has points of resemblance throughout the family. 
The simplest type of stele is a solid cylindrical strand of pitted 
scalariform tracheids containing no parenchyma and surrounded by 
phloem. This is found in the genera Grammatopteris and Tubi - 
caulis. It is probably the real “ protostelc,” i.e., the most primitive 
type of vascular strand found in the axis of vascular plants. Spiral 
protoxylem has not been detected in these types, but, judging from 
other members of the family and from the analogy of modern ferns, 
that is probably because growth in length was not rapid. Some 
elements are narrower than others, but there is no particular 
evidence that these represent protoxylem. 
The mixture of transversely elongated and more or less isodia- 
metric pits (Fig. 1) in many of these forms is of interest. Miss 
Stopes 1 has suggested that the possession of circular pits, a 
character shared by the Cycadofilices, some Ophioglossacege and 
Gymnosperms, is a sign that the Botryopteridege are a step in 
advance of the typical ferns, which possess only scalariform 
tracheids. It is significant however that both long and short types 
1 Stopes, ’06. 
