24 Lady Isabel Broxtfrid. 
on a receptacle, to the frequently coherent exannulate sporangia of 
the Marattiacete that always originate simultaneously. Loxsoma 
differs from the Marattiaceae in the same ways as the Cyatheaceae 
and Polypodiaceae, and its stele affords none of the homoplastic 
similarities to the Marattiaceae found in the polycyclic forms of both 
these orders. 
Dr. Campbell remarks that the Osmundaceae are undoubtedly 
intermediate between Eusporangiatae and Leptosporangiatae, but 
that it is difficult to say whether they come closer to the Ophio- 
glossaceae or Marattiaceae. He concludes that all these forms spring 
from one type, but that no two are directly related (13). Professor 
Bower also holds that in size, structure, and mode of origin of the 
sporangia, the Osmundaceae are intermediate between the Lepto- 
sporangiate forms and the Marattiaceae (6). The sub-eusporangiate 
origin of the sporangia of the Osmundaceae may well be a primitive 
character retained by them and the Marattiaceae from their common 
ancestor, for the small sporangia of the Leptosporangiatae are the 
only Pteridophytic sporangia that originate from a single cell. It is 
hard to say whether the endarchy of the phloem in the Marattiaceae 
and Osmundaceae, unknown in other Ferns, is a primitive character, 
or whether it originated independently in the two orders. Mr. Gwynne- 
Vaughan’s view that the two cases are not strictly comparable 
supports the latter alternative (21). In any case the geological 
history of the stele of the Osmundaceae fully bears out Dr. Campbell’s 
view that there is no direct connection between the latter order 
and the Marattiaceae. 
The Marattiaceae show but few resemblances to the Salviniaceae 
or Marsileaceae, but to the Psaronieae their likeness is curiously 
exact. The elongation of the steles of the Psaronieae and the 
presence in them of purely cauline tracts of tissue are due to the 
fact that, unlike the Marattiaceae, whose phyllotaxy is usually spiral, 
the leaves, and therefore the leaf-gaps separating the meristeles, are 
disposed in few more or less widely separated orthostichies. In the 
dorsiventral Kaulfussia, however, the leaves are confined to the 
dorsal part of the rhizome and the ventral part of the vascular 
system remains purely cauline. The “ peripheral steles ” of the 
Psaronieae are absent from the Marattiaceae, but as these do not 
occur in the older species of Psaronius with distichous phyllotaxy 
they are probably a later development of the more modified species. 
Rudolph’s researches have done much towards re-establishing the 
comparison between the root-traversed cortices of the Psaronieae 
and Marattiaceae. Among other similarities between the two orders 
