Anatomy of the Ophioglossaceae. /. 227 
interest for comparison with other Ferns, and especially with Helmintho- 
stachys. 
The structure and vascular relations of the first branched specimen will 
be readily understood from the transverse sections at different levels (Text- 
fig. 10), together with the reconstruction of the stele (Text-fig. 11). Three 
transverse sections at different levels are shown in Phots. 29-31. The 
reconstruction of the vascular skeleton is to the same scale as those of the 
unbranched plants above. The outline cross-sections are, however, drawn 
to a slightly smaller scale, and show the cortex as well as the stele. The 
branch was evidently borne on a small plant the apex of which had been 
destroyed. The stele of the main axis is small, and at the level where the 
series begins shows the leaf-gap left by the departing trace, to which the 
branch is related. This leaf-gap has a deeply extending, but incomplete, 
internal endodermis (Text-fig. 10, a ) ; this diminishes in extent before the gap 
in the endodermis closes (#, c ). The endodermis of the departing leaf-trace 
becomes complete on the side towards the stele ( b ). As this takes place, 
tracheides destined to supply the branch begin to appear at first to either 
side of the xylem of the trace ; they ultimately form an adaxial curved 
band joining the two ends of the leaf-trace xylem (c). This stage is repre- 
sented in Phot. 29. The adaxial xylem increases in amount and becomes 
separate from the xylem of the trace, first on one side (Text-fig. 10, d , e ; 
Phot. 30), and ultimately on the other also. Even before it is completely 
detached, the xylem of the branch arranges itself in the form of a medullated 
stele with scattered tracheides in the pith (Text-fig. 10,^ ; Phot. 31). Until 
this stage the stele of the branch has been enclosed by an endodermis 
common to it and the subtending leaf-trace, but the endodermis outside the 
latter now becomes indistinct and disappears. The endodermis becomes 
complete around the branch stele as this separates from the leaf-trace, but 
previously the endodermis on the adaxial side of the branch has become 
continuous with that of the main axis (Text-fig. 10, e,f\ Phot. 31). Not only 
is this the case, but tracheides are developed between the xylem of the main 
stele and that of the branch, so that the xylem of the two is continuous for 
a short distance (Text-fig. io, e\ Phot. 31). Above this the two steles 
again separate, and each has its own complete endodermis (Text-fig. io,^*). 
A little higher the stele of the main axis disappears and the branch alone 
remains (k). 
Before tracing the stele of the branch further the structure of the stele 
of the main axis must be described. It was mentioned above that this had 
an imperfect but extensive internal endodermis continuous with the external 
endodermis at the leaf-gap (Text-fig. 10, a). The outer endodermis then 
becomes complete, the inner endodermis disappearing (b, r, d) ) and later the 
xylem-ring is practically completed (<?,/). Just at this level the connexion 
with the xylem of the branch takes place. From a little below the closure 
