The Botryopteridece. 61 
bundles supplying the branches of the frond arise from these 
outer bands. 
In Z. duplex, described by Williamson, the strand is hour-glass 
shaped in section, having a longitudinal furrow at each end (Fig. 
13). When branches are about to be given off the cusps on each 
side of this furrow reach out towards the middle line (horizontal 
plane of the whole strand) and are cut off from the strand, tem¬ 
porarily fusing with one another across the furrow and then again 
separating before passing out; so that here again we have a pair of 
Fig. 9. Fig. 10. 
Fig. 9. Zygoptcris Bibractensis. Diagram of petiolar strand, c.x., central 
bar of xylern, l.x., lateral bands of xylem, e.x., external xylem of lateral bands, 
separated from the rest by internal parenchyma (i-p.), ph. crushed phloem, etc. 
After Scott. 
Fig. 10. Zygopteris Lacattii. Strand of rachis showing departure of branch 
bundles. From Renault. 
bundles given off on each side of the rachis. In the Diplolabis 
esnotensis of Renault (Fig. 14) the strand is of the same general 
form, though it is more X-shaped, connecting the •* duplex -type ” 
with the H-shaped, and the branch strands are given off in 
essentially the same way. 
The vascular strands of the fronds known as Stauropteris 
oldhamia , Binney, closely allied to, if not actually to be included in 
the Botryopterideae, are also related to this type. The fronds 
themselves are much branched and are apparently without lamina. 
We do not know if they are exclusively fertile fronds belonging to a 
dimorphic type or if they are true “ trophosporophylls,” but in some 
cases the ultimate branchlets, which arise in clusters, possibly by 
much condensed shortened dichotomies, end in sporangia. The 
xylem is cruciate, “ the phloem filling up the bays between the 
xyem-arms, and sometimes extending to the middle so as to break 
up the wood” more or less completely (Fig. 16). The xylem is 
exarch and the branch bundles are given off from the protoxylems 
