2\2 Lang. — Morphology and Anatomy of the Ophioglossaceae. 
Phot. 17. Section a little higher up than the preceding photograph. The endarch leaf-trace 
has separated from the stele. A root-trace is attached to one side of the leaf-gap. x 62. 
Phot. 18. Transverse section of a small leaf-trace on its way through the cortex. The endo- 
dermis is complete adaxially and a number of adaxial tracheides are present, continuous on the right 
side with the curved extension of the xylem of the original leaf-trace, x 62. 
Phot. 19. Transverse section of a large leaf-trace on its way through the cortex; scattered 
adaxial tracheides are present on the concave inner face of the trace, x 62. 
Phot. 20. Longitudinal section of a leaf-trace passing through the cortex from an adult stele 
with marked secondary thickening. At the lower end of the photograph the leaf-trace shows shorter 
and wider secondary tracheides to the outside of the primary xylem ; these disappear higher up. 
Two adaxial tracheides are seen to the inner side of the primary xylem of the trace, x 62. 
Phot. 21. Transverse section of a leaf-trace in the base of the petiole. The xylem has just 
divided into two and shows the hooks, interpreted as the last indication of the adaxial xylem ; the 
hook on the right is most clearly seen, x 62. 
PLATE XXI. 
Phot. 22. Longitudinal section of an adult stem with secondary thickening. From right to 
left the photograph shows : pith, primary xylem, secondary xylem, conjunctive parenchyma, phloem 
(represented by a crushed sieve-tube), and pericyclic xylem. The tracheides of the latter are short 
and arranged in groups which indicate their origin by irregular tangential divisions in the pericycle. 
x 62. 
Phot. 23. Transverse section of part of the stele of the rhizome of the second branching 
specimen. Pericyclic xylem is developed and lies outside the phloem, x 62. 
Phot. 24. Transverse section of the leaf-trace subtending the branch of the second branching 
specimen. An almost complete band of pericyclic xylem is present outside the phloem on the 
abaxial side of the trace, x 62. 
Phots. 25, 26. Longitudinal radial sections of the rhizome, showing the position and appearance 
of the enclosed vestigial axillary buds, x 35. 
Phot. 27. Transverse section of the stele of the adult region of the rhizome, showing a departing 
leaf- trace and the axillary slit leading down to the vestigial axillary bud. x 40. 
Phot. 28. Transverse section of another rhizome passing just below the level of the axillary 
slit, i.e. through the region in which the apex of the vestigial bud is probably situated, x 62. 
Phots. 29-31. Three transverse sections of the first branching specimen. In Phot. 29 the 
adaxial xylem of the subtending leaf-trace is completed. In Phot. 30 this has separated on one side 
from the leaf-trace and is becoming arranged to form the stele of the branch. In Phot. 31 the 
branch stele is still connected with the xylem of the subtending leaf-trace, but has also become 
continuous with the xylem of the main axis. Tracheides have developed throughout the pith of the 
main axis. x 40. 
Phots. 32-34. Three transverse sections of the second branching specimen. In Phot. 32 the 
subtending leaf-trace shows the pericyclic xylem. In Phot. 33 this has almost disappeared, but the 
band of adaxial xylem to supply the branch is complete. In Phot. 34 the adaxial xylem has 
separated from the subtending leaf-trace as an irregular group of tracheides from which the branch 
stele will be organized, x 40. 
Phots. 35, 36. Two transverse sections of the third branching specimen. In Phot. 35 the 
adaxial xylem forming the stele of the branch is still connected with the subtending leaf-trace and 
also with the xylem of the main stele in the neighbourhood of the leaf-gap. In Phot. 36 the 
subtending leaf-trace is departing, but the stele of the branch is still in connexion with the xylem of 
the main stele, x 40. 
Phot. 37. Longitudinal section of the fifth branching specimen, showing the departure of the 
subtending leaf-trace from the injured main stele, and the development of short tracheides adaxially 
to the leaf-trace. These were the first indications of the vascular supply to an axillary branch which 
had been broken off. x 40. 
