ANATOMY 463 
system of the axis: comparison with the Ferns shows that in them the 
concrete leaf-trace is characteristic of the primitive types, and that its 
separation into many distinct strands is a feature of those which are later 
and derivative. ‘This analogy strongly supports 
the view that the state of the leaf-trace in 
§ Ophiderma is not primitive. 
Passing up the petiole the vascular strands 
undergo branchings, which vary in extent a 
according to the dimensions of the fully formed 
leaf. The strands arrange themselves in an ae 
approximate circle in the transverse section, 
while those on the adaxial side pass out into 
the fertile spike. The details are various: the 
simplest is in the small O. Bergzanum, where 
the single leaf-trace strand may long remain 
undivided, giving off two lateral strands which 
fuse on the adaxial side to form the supply 
for the spike: further up the strands of both 
sterile lamina and of fertile spike may branch 
again. In the larger species of Ophzoglossum 
the plan is the same, but with the difference 
that the branching is more profuse, and takes 
place before the lateral supply is given off 
right and left for the fertile spike; in the Ge.) 
larger species the latter consists not of a single i 
strand but of several. ‘The same is the case 
2 
for O. pendulum, and even for O. palmatum 3. 
in the case of the lowest spike, though .in the FIGs 256: 
u i ly is 1 j Nos. 14-16 successive transverse 
Poe spikes nae BE ee eee regular 1 sections of leaf of O. sSalmatum, 
accordance with the indefinite positions which showing the origin of the vascular 
supply to the lowest of its spikes. 
they hold (Fig. 259, 14-17). In Ophioglossum 17=transverse section-of the stalk of 
‘ js i that spike. 18-23=successive sections 
there is a strong median strand in the leaf, higher up on the same leaf, showing 
which frequently holds its own throughout pe ee ee a 
the complicated reticulations of the expanded 
blade. In Botrychium, however, the broad strap-shaped leaf-trace forks 
early; and from the adaxial margins of each limb branch-strands are 
given off, which form the supply of the fertile spike: subsequently 
both systems may branch further, showing dichotomous characters, and an 
ultimate “‘ Weuropteris” venation. In Aelminthostachys the first branchings 
of the leafstrand are described as dichotomous; the resulting strands 
arrange themselves in a ring, and traverse the petiole with occasional 
anastomoses. Where the leaf branches complex anastomoses occur, 
resulting in a fairly regular vascular supply passing into each branch. 
The spike receives four or five strands, arranged in a circle, in its 
transverse section. Further branchings occur in both sterile and fertile 
