7 
Anatomy of the Ophioglossaceae. III. 
the gradual arching out of the leaf-trace xylem (Text-fig. 2, A, B, c), its 
separation from the xylem-tube first on the side away from the middle line 
of the stele (d, e), and shortly afterwards on the median side also. At this 
level (Text-fig. 3, f) the trace is distinct from the stele as regards its 
xylem and phloem, but is still enclosed by the unbroken stelar endo- 
dermis. On the other side of the middle line the previous leaf-gap is seen 
to have closed, the disturbance of the xylem to have subsided, and the 
Text-fig. 2. Series of transverse sections of the stele of a large rhizome, to show the early 
stages of departure of a leaf-trace and the closure of the leaf-gap of the preceding leaf and the 
development of a well-marked vestigial branch stele. Further description in text, l.t., leaf-trace; 
ph.y phloem ; e outer endodermis; e.i., internal endodermis ; x.o. f outer xylem ; x.L , inner xylem ; 
x.o.br ., outer xylem of vestigial branch; x.i.br., inner xylem of vestigial branch ; v.b., inner end of 
canal to vestigial bud; e.b., endodermis in relation to vestigial bud. 
section passes through the inner end of the canal leading down to the 
vestigial bud. 
The leaf-trace itself as it separates from the stele is mesarch, although 
the inner xylem is much less developed than in the stele of the rhizome. 
The trace in this large rhizome thus agrees with that described and figured 
by Sinnott, but, as will be seen below, this is by no means the only type of 
trace found in Helm in thostachys. 
The further changes undergone by the trace of this rhizome as it 
passes obliquely through the cortex are illustrated in Text-fig. 3 ; this 
represents the preceding trace, and is therefore on the other side of the 
