June, 1921] 
CAMPBELL THE EUSPORANGIATE FERNS 
When one compares the slender rhizome of such ferns as Lygodium, 
Gleichenia, and many Hymenophyllaceae with the large and highly developed 
leaves, it may well be questioned whether the leaves should be regarded as 
mere appendages of the relatively insignificant axis. This is particularly 
the case with such forms as Gleichenia and Lygodium whose leaves show 
almost unlimited power of continuous growth in length. 
It is very important that further studies upon the origin of the stelar 
tissues of the Leptosporangiatae should be undertaken. Most of the 
studies already made upon the ontogeny of these ferns have not dealt with 
the earliest stages of the stelar tissues, but have started with the fully 
developed stele of the young sporophyte, assuming that this axial stele is 
really of cauline origin and not a composite structure derived from a fusion ot 
leaf-traces. In order to solve this question it is necessary to examine series 
of sections, both transverse and longitudinal, including the growing point of 
the stem and the adjacent regions. In longitudinal sections alone there is 
danger of misinterpretation, as the traces of the youngest leaves may be 
easily mistaken for a true cauline stele; but if corresponding transverse 
sections are examined, it is then possible to determine whether or not there 
is a stele, of strictly cauline origin. 
It will not be surprising if such a test applied to the Gleicheniaceae 
and Hymenophyllaceae will show that the solid or tubular axial steles are 
in reality composed of coalescent leaf-traces as they are in Botrychium and 
in the young sporophytes of some of the Marattiales. 
It is very desirable that the many careful studies of the stelar tissues of 
the ferns be reviewed to determine whether the usual interpretations of 
the relation of the tissues of the leaves and axis are tenable. A satisfactory 
solution of the problem necessitates an examination of the origin of the 
tissues in the young sporophyte as soon as it emerges from the gametophyte, 
and a further study of the building up of the stelar structures as new leaves 
are developed, tracing the origin of the individual vascular strands to their 
beginning. Reconstructions from series of cross sections of the completed 
bundles of older stages will not suffice. 
Conclusion 
The presence of a single cauline stele — ''protostele," /'siphonostele," 
''dictyostele" — is not borne out by the history of the stelar tissues in the 
Ophioglossales and Marattiales. In all of these the stelar system begins as a 
single strand common to the first leaf and root ; the stem apex arises adven- 
titiously in Ophioglossum Moluccanum and 0. pendulum, and is very in- 
significant in Botrychium and the Marattiales. No procambium is de- 
veloped in the stem region in the young sporophyte. 
In the Ophioglossales, the stelar structures of the axis are built up ex- 
clusively of leaf-traces to which the bundles of the roots are joined. This 
condition obtains also for the earlier stages of the Marattiales, but is com- 
