239 
Anatomy of the Opkioglossaceae . I, 
adult stelar structure in Helminthostachys , where inner and outer primary 
xylem are well developed. The two xylems appear to be strictly com- 
parable to the outer and inner xylem in Zygopteris , and possibly to the 
outer and inner xylem in Osmundaceae. In B. Lunar ia the outer primary 
xylem is well developed throughout the plant, while the inner xylem is, as 
a rule, only represented by a few tracheides round the periphery of the pith, 
which occupies its place in the expanded stele above the basal region. The 
secondary xylem comes immediately outside the primary, and there is 
no absolutely sharp distinction between the two. The relation between 
primary and secondary xylem is comparable to what is described for 
Botrychioxylon 1 and for Zygopteris corrugata . 
The medullation of the stele has been examined in detail, since it 
appeared to be important to ascertain all facts which would throw light on 
the significance to be attached to the presence of an internal endodermis 
in the lower region of the rhizome. The view reached, that the pith is 
throughout intrastelar, and that the internal endodermis is a new formation 
and does not mark a morphological boundary, makes the pith in the Ophio- 
glossaceae strictly comparable to the parenchyma enclosed by the xylem in 
the Zygopterideae. It would also be comparable to the pith of the Os- 
mundaceae, as the origin of this is explained by Kidston and Gwynne- 
Vaughan, and to the pith of the Schizaeaceous stele as interpreted by 
Boodle. The conclusion to which my observations point, that the pith in 
the Ophioglossaceae is not due to ‘ pocketing ’ or ‘ intrusion of cortex but 
is wholly intrastelar, goes beyond that of Bower. He accepted the endo- 
dermis provisionally as marking the limit between pith and cortex, and 
thus arrived at the view that the pith in Botrychium was in the basal region 
intrastelar, and in the upper portion of the plant largely intrusive and cortical. 
The further facts given in this paper appear inconsistent with any actual 
intrusion of cortex. The Ophioglossaceae would thus come into line in 
this respect with all the relatively primitive groups of Ferns, and the 
excellent statement recently made by P. Bertrand 2 on the nature of the 
differentiation of the procambium to form either a solid column of xylem, 
a medullated stele, or one with internal endodermis and phloem would apply 
to the Ophioglossaceae as well as to the Osmundaceae. 3 
The leaf-trace has been shown to exhibit a tendency to the completion of 
its ring of xylem by the development of adaxial tracheides extending from the 
ends of the arc of xylem which leaves the stele of the stem. Since any indica- 
tion of centripetal xylem disappears before the leaf-trace departs from the stele 
of the stem, it does not appear that the adaxial xylem of the leaf-trace is 
1 Scott, Trans. Linn. Soc., vol. vii, pp. 373 ff. 2 Progressus Rei Botanicae, iv, p. 208. 
8 The facts ascertained for Botrychium Lunaria appear to be irreconcilable with the statement 
of Jeffrey ‘ that the pith must in all cases be regarded as a derivation of the cortex’ (Bot. Gaz., Dec. 
1 9 10 , p. 412). But the general question has been sufficiently discussed by Bower (Ann. Bot., 
xxv, p. 555). 
