236 Lang. — Shi dies in the Morphology and 
vascular connexions for its branches should show so much in common with 
the primary structure in the branches of the groups mentioned. 
Summary. 
1. Complete rhizomes of Botrychium Lunaria exhibit some variety in 
external form. Above the basal region with its crowded roots an ill-defined 
segmentation of the shoot can be traced ; this is marked by the origin of 
one or two roots just above the leaf-gap, i. e. near the base of the segment 
of the shoot corresponding to the next leaf. The transition from the basal 
to the adult regions of the rhizome may be a gradual and direct one, none 
of the segments being especially elongated. In other cases a marked 
intermediate region, due to one or a number of segments being greatly 
extended and slender, may intervene between the basal and adult regions. 
2. The medullation of the stele may take place without interruption of 
the external endodermis at the lower leaf- gaps, and without the develop- 
ment of an internal endodermis in any part of the plant. The band of 
endodermis closing the gap caused by the departure of a leaf-trace is 
a new formation, and may be developed before the internal endodermis is 
interrupted. 
When an internal endodermis is present it is confined to the slender 
intermediate region of the rhizome, and may be more or less complete. It 
does not form a complete pocket extending down from the leaf-gap, and 
its distribution suggests a new formation to meet physiological needs, 
rather than the intrusion of a phloeotermal layer marking the inner limit 
of an intrusive cortex. The pith of Botrychium Lunaria is therefore regarded 
as wholly intrastelar and not as intrusive, whether an internal endodermis 
is present or not. This view is supported by the relations of the tissues in 
the apical region. 
3. Centrifugal (or outer) primary xylem, centripetal (or inner) primary 
xylem, and secondary xylem can be distinguished in the stele of B. Lunaria. 
In the non-medullated stele of the basal region the group of central 
tracheides is surrounded by a zone of tracheides showing indications of 
radial arrangement. On medullation taking place elements of the central 
xylem can still be recognized on the inside of the cylinder of outer xylem, 
and may occur scattered through the pith. Only primary xylem is present, 
and this also holds for the more or less specialized intermediate region of 
the rhizome. The transition to the fully adult region is marked by the 
appearance of tracheides arranged in regular radial rows immediately 
outside the centrifugal primary xylem. The medullary rays present in the 
zone of secondary xylem are cut off from the pith by the continuous zone 
of primary xylem. 
The xylem is completely developed and lignified a short distance 
behind the apical meristem. No sharp limit can be drawn between the 
