4 o 8 Chandler . — On the Arrangement of the Vascular Strands 
regalis , and it follows that the pith of this species must be regarded 
as belonging to the central cylinder, as maintained by Van Tieghem. 
On the other hand, Faull’s work clearly shows that the pith of O. cin- 
namomea is extra-stelar in nature. Consequently we must regard the 
pith in these two members of the same genus as of different morphological 
value, and the vascular arrangements in the two cases as fundamentally 
distinct. To some, the acceptance of this view would be a matter of 
difficulty, but it is by no means impossible to find a parallel, an almost 
equally striking difference in the arrangement of the vascular tissues 
occurring in the genus Anemia , where, in A. mexicana we have a solenostelic 
vascular system, in A. Phyllitidis a typical dictyostelic arrangement, and 
in A. aurita an arrangement closely approximating to that of Lygodium. 
If the validity of the above interpretation of the vascular systems of 
Osmunda regalis and O. cinnamomea be admitted, then it follows that the 
vascular organization of O. regalis is the more primitive, and that the type 
occurring in O. cinnamomea is less so. 
The vascular organization of O. cinnamomea , therefore, may be re- 
garded as having been evolved in two alternative ways ; either as a result 
of degeneration from a typical siphonostelic structure, or, on the other hand, 
it may represent an intermediate halt on the direct line of advance to 
dictyostely. For reasons already given, the writer is inclined to regard 
the latter view as the more probable. 
To sum up. As a result of the study of certain leptosporangiate 
ferns, the writer has been led to conclude that : — 
(a) in dealing with questions of a so-called stelar character, we must 
confine our attention to tissues of two categories only, viz., vascular and 
non-vascular ; 
(i b ) the primitive type of vascular system in the ferns is a solid rod of 
vascular tissue, which may be a solid xylem strand surrounded by phloem, 
or an amphiphloic strand ; 
(c) the complex dictyostelic structure results from the moulding and 
elaboration of this solid vascular strand, the moulding and elaboration 
being largely due to the necessity for an efficient attachment of the leaf- 
traces ; 
(d) the differentiation of ground-tissue pockets plays an important 
part in such elaboration ; 
(e) the development of the vascular system proceeds along certain 
well-defined lines, and that practically all the intermediate stages have 
been adopted by different plants as most suited to their individual mature 
requirements ; 
(f) the ontogeny of the vascular system strikingly resembles what 
we must suppose to have been its phylogeny. 
