Anatomy of the Ophioglossaceae . /. 
241 
DESCRIPTION OF FIGURES IN PLATES XX AND XXI. 
Illustrating Prof. Lang’s paper on Botrychium Lunaria. 
(All these figures are from untouched photographs.) 
PLATE XX. 
Phot. t. Transverse section of medullated stele in the intermediate region of the rhizome. 
Practically all the xylem is centrifugal and primary, x 62. 
Phot. 2. Transverse section of a stele showing the transition to the region with definite 
secondary thickening. Radial rows of secondary tracheides are developed irregularly outside the 
narrow zone of centrifugal primary xylem. x 62. 
Phot. 3. Transverse section of the stele of the adult region of the rhizome. Around the zone 
of primary wood (in which centripetal as well as centrifugal xylem may be represented) comes 
a broad zone of secondary xylem consisting of radial rows of tracheides and medullary rays which 
only extend inwards as far as the primary xylem. x 35. 
Phot. 4. Portion of the vascular ring of a similar stele more highly magnified. The distinction 
of primary and secondary xylem is well shown, x 62. 
Phot. 5. Portion of the vascular ring of the stele in Phot. 3, showing the primary and 
secondary xylem. Some of the primary xylem next the pith may be centripetal, x 62. 
Phot. 6. Transverse section of a stele at the base of a plant. The solid xylem consists mainly 
of central tracheides around which elements of the outer xylem are commencing to appear, x 62. 
Phot. 7. Transverse section of the stele of the same plant at a slightly higher level. The 
solid xylem consists of the central group of tracheides, and around it the tracheides of the outer 
xylem arranged more or less radially. A root-trace is departing from the stele, x 62. 
Phot. 8. Transverse section of the same stele at a still higher level. Parenchyma has appeared 
in the central xylem forming the beginning of the pith. The xylem is mostly composed of the outer 
xylem with elements of the inner xylem around and between the pith-cells, x 62. 
Phot. 9. Similar section of the stele of another plant. The two pith-cells in the centre are 
surrounded by the inner xylem, outside which comes an incomplete zone of tracheides of the outer 
xylem. x 62. 
Phot. 10. Transverse section of a stele near the base of a plant, showing on the right a leaf- 
trace about to depart. A tracheide of the inner xylem lies opposite the leaf-gap and marks the 
boundary between the pith and the 'pocket’ of parenchyma internal to the departing trace, x 62. 
Phot. 11. Transverse section a little higher up than Phot. 10. The leaf-trace has separated 
from the stele but is still enclosed by the endodermis. Tracheides of the inner xylem have com- 
pletely shut off the pith from the leaf-trace ‘ pocket ’. The stele in this and the preceding photograph 
has a second endodermis some three cells further out in the cortex, x 62. 
Phot. 12. Transverse section of a stele showing a small pith, and to the left a large parenchy- 
matous ‘ pocket ’ internal to a leaf-trace which is about to depart, x 62. 
Phot. 13. Transverse section slightly higher up than Phot. 12. The xylem of the trace has 
separated and the parenchymatous pocket forms a gap in the outer xylem only. The central xylem 
has become solid again ; there is no true pith. x 62. 
Phot. 14. Section a little higher up than Phot. 13. The xylem of the trace is further out 
but still enclosed by the stelar endodermis. The gap in the outer xylem persists. The pith of the 
stele is reappearing, x 62. 
Phot. 15. Section still higher up than the preceding photograph. The pith has increased, 
almost replacing the central xylem, and communicates with the parenchyma of the gap in the outer 
xylem, which is almost closed. The leaf-trace is seen dying out in the cortex. A root-trace is 
attached to the xylem of the stele below, x 62. 
Phot. 16. Transverse section of the stele of the same plant as Phots. 12-15, but much higher 
up. The zone of xylem is wholly primary. The tracheides projecting into the pith correspond to 
elements of the central xylem. They disappear internal to the leaf-trace which is preparing to 
depart on the left, x 62. 
