Origin of Medullation in ihe Ophioglossaceae . 
553 
PLATE XLVI. 
Fig. 17. Transverse section of the stele of an injured plant of B. ternatum ,, in the region below 
the injury, showing the slightly compressed stele with a large parenchymatous pith, x about 50. 
Fig. 18. A section from the same plant at the level of the injury. The stele is seen greatly 
contracted, with irregular xylem outside it. Internally the contracted pith contains isolated 
tracheides. x about 50. 
Fig. 19. The central part of the above, showing more in detail the relation between the 
tracheides and the parenchyma cells, x 144. 
Fig. 20. Another section of the same, showing isolated tracheides lying centrally in the pith, 
x 144. 
Fig. 21. A section above the damaged region, showing the normal structure resumed, though 
the tissues are rather less bulky than those of the original stock below the injury, x about 50. 
Fig. 22. Photograph of one of Professor Farmer’s sections of a small rhizome of Helminthostachys 
zeylanica for comparison with Figs. 19 and 20 of B. ternatum. x 144. 
