53 
Anatomy of the Ophioglossaceae . Ill. 
(Cf. Text-fig. 4.) In Photo 22 the endarch leaf-trace is departing, its protoxylem being seen at px. 
x . 2 indicates one of the two groups of accessory xylem, while x.i, points to the inner xylem extending 
into the leaf-gap and destined for the branch. In Photo 23 the inner xylem has passed through the 
gap and approximated to the uniting groups of accessory zylem. In Photo 24 the stele of the 
branch is fully constituted and lies beside the broken-down stele of the parent fragment of rhizome, 
x 67. 
Photo 25. Transverse section of the stele of the second branching specimen after the branch had 
passed off. The stele shows outer and inner primary xylem, and outside the former accessory or 
secondary xylem is present all round the stele, x 25. 
Photo 26. Portion of a similar section more highly magnified, showing the relations of the 
accessory or secondary xylem to the primary xylem. x 67. 
Photos 27-29. Stages in the departure of the vascular supply from the second branching 
specimen. (Cf. Text-fig. 6.) x 67. Photo 27 shows the great development of accessory or 
secondary xylem to the sides of the closed leaf-gap. It is uncertain whether the xylem marked ? is 
to be regarded as inner xylem passed into the gap, as in the first branching specimen. Photo 28 
shows the arc of accessory xylem destined to form the outer xylem of the branch completed over 
the closed gap. Extending into it are the narrow tracheides of the inner xylem mixed with paren¬ 
chyma. Photo 29 shows the basal region of the stele of the branch in longitudinal section, and 
the continuity of its outer and inner xylem respectively with the tissues recognized in Photo 28. 
PLATE III. 
Photos 30-34. Stele of the first branch in transverse section, showing the preparation for the 
separation of the first leaf-trace and the position of its protoxylem (Photo 30) ; a later stage on 
the separation of the xylem of the first leaf-trace (Photo 31) ; the first leaf-trace, with its xylem 
completed adaxially, lying beside the xylem of the stele of the branch, which has now regained its 
complete structure (Photo 32) ; the stele of the branch after departure of the first leaf-trace and at 
the level of the vestigial bud (Photo 33) ; and a later stage in the preparation for departure of the 
second leaf-trace, the protoxylem of which was evident in the preceding photograph (Photo 34). 
x 67. 
Photo 35. Longitudinal section of the basal portion of the second branch, showing the departure 
of the leaf-trace, which leaves a gap in the outer xylem ; the inner xylem is continuous along the gap 
and separates the pith from the parenchyma in the angle of the departing trace. The inner xylem 
consists of spiral tracheides, while those of the outer xylem are pitted, x 67. 
Photos 36-39. Stele of the second branch in transverse section, showing the stages in initiation 
and departure of the second leaf-trace. In Photo 36 the first leaf-trace is seen divided in the 
cortex, the stele is medullated, and the protoxylem of the second leaf-trace is recognizable in its 
xylem ; the inner xylem is almost entirely replaced by pith. In Photo 37 the endarch xylem of the 
second leaf-trace has separated, and elements of inner xylem have developed below the gap left 
in the tube of outer xylem. In Photo 38 this development of inner xylem is still more marked, and 
inner xylem is seen in the lower part of the stele, where a root is attached. In Photo 39 the leaf-trace 
is separate and has its complete endodermis; the inner xylem of the stele, which has returned to the 
condition shown in Photo 36, has largely disappeared, and the protoxylem of the third leaf-trace 
is evident in the xylem tube, x 67. 
Photos 40-46. Transverse sections of the stele of a young plant developed from an embryo, 
showing the changes involved in the separation of the first and second leaf-traces. Photo 40 shows 
the stele low down in the hypocotyl, with a central group of inner xylem surrounded by an irregular 
zone of outer xylem. Photo 41 shows the group of parenchyma cells internal to the arc of outer 
xylem destined for the first leaf-trace ; the protoxylem of this is endarch. In Photo 42 the first trace 
has separated, and the xylem of the stele has again become solid. In Photo 43 most of its inner 
tracheides are replaced by parenchyma, while the second leaf-trace is initiated as an endarch arc of 
the outer xylem. Photo 44 : the trace is not separate, but the increased development of inner xylem 
in the stem stele has filled up the gap to be formed in the outer xylem when separation takes place, 
and rendered the stem stele almost solid. Photo 45 shows a slightly further stage, the trace xylem 
not being completely free, while the outer xylem of the stem stele is reconstituted around the central 
group of inner xylem. In Photo 46 pith is again appearing by the replacement of most of the inner 
tracheides by parenchyma ; the protoxylem of the third leaf-trace is evident, x 130. 
