22 
Lang,—Studies in the Morphology and 
regarded as inner xylem protruded into the gap, or whether the outer xylem 
was complete across the gap, could not be determined with certainty. Com¬ 
parison with the first branching specimen would favour the former 
Text-fig. 6. Series of transverse sections of the stele of the second branching specimen, showing 
the departure of a leaf-trace on the right-hand side, the distribution of the accessory or secondary 
xylem, and the stages in closure of the leaf-gap on the left-hand side, and the relation to it of the base 
of the branch stele. The accessory xylem is cross-hatched. Further description in text. 1 -gO, leaf- 
gap in relation to branch ; l.t?, next leaf-trace from rhizome ; x.i., inner xylem; x.o., outer xylem ; 
x . 2 , accessory or secondary xylem; ?, possible extension outwards of inner xylem; x.o.br ., outer 
xylem of branch ; x.i.br ., inner xylem of branch ; l.t.br ., first leaf-trace of branch. 
interpretation. The actual appearance in this critical region is shown in 
PL II, Photo 27, the groups of tracheides which are doubtfully regarded 
as projecting inner xylem being marked ?. The photograph further shows 
