524 FILICALES 
of Hawlea or Angiopteris would readily result from individual growth of 
the sporangia already initiated. This seems more probable than a fusion 
of sporangia originally separate, of which there is no structural evidence in 
the synangia themselves. 
An indirect argument that the synangium was the primitive type is to 
be found in comparison of the spore-output. It is much larger from the 
single sporangium of the synangial types, such as Kaulfussia or Ptychocarpus, 
than from the separate sporangia, such as Angiopteris. It will be shown 
below that in the Ferns at large a progressive reduction of spore-output 
from the single sporangium has accompanied specialisation. If the experience 
from comparison of other Ferns hold good for the Marattiaceae, then the 
larger output per sporangium in the synangial types would show them to 
be the more primitive, while the polysporangiate type with its smaller 
output would be the more advanced. The question is one incapable of 
present demonstration, but the comparative and developmental evidence 
supports the view as stated here. 
In conclusion, it is impossible to avoid the comparison of the Maratti- 
aceous sorus with the sporangiophores of other Pteridophytes: the vascular 
stalk or receptacle, the arrangement of the sporangia upon it, the relations 
of the sporangia, their radial dehiscence—all find their correlatives else- 
where. The chief differences are in the number of the sori, and their 
position relative to the parts of the shoot which bear them. But in 
view of the various positions which the sporangiophores hold in the 
strobiloid Pteridophyta this cannot be held as invalidating the comparison 
of them with these primitive sori. It may be that the similarity is a 
result of parallel development; but if that be so, it would still appear 
probable that the evolutionary progressions which produced them were 
of a like kind. It will probably be objected that many of the early Ferns 
show isolated sporangia of large size, and that this precludes any general 
application of a primitive soral state for Ferns of the Palaeozoic Period. 
In reply to this, it may be remarked that the genus Sphenophy//um illustrates 
how a “monangial” condition may probably arise from an originally soral 
state. The sporangiophores with four or more sporangia are seen in 
Cheirostrobus and in S. majus: and smaller numbers in other species 
lead to the solitary sporangium of S. Dawsont (see p. 425). A reduction 
of like nature is seen in the sori of Gleicheniaceae, and may probably 
explain also the solitary sporangia of the Schizaeaceae, as indicated by 
Prantl. Senjftenbergia is itself an early example (Fig. 289 a). These early 
forms must be given full consideration in elucidating the Fossils: they 
indicate the probability that in early Pteridophytes a monangial state 
may have been derived from a polysporangiate sorus or sporangiophore. 
ANATOMY, 
The vascular system of the shoot in certain of the Marattiaceae is 
well known to be among the most complicated of all the Pteridophytes. 
