A r otes. 
489 
sporogenous tissue of one sporangium to a single parent cell. 
A special study of the irregularities has been made in Danaea , in 
which genus they are most marked ; incomplete septa are frequent, 
and the sporangia are of very unequal size. The main features have 
already been noted in the preliminary statement on that genus, where 
it has been pointed out that comparison of the details with those of 
the septate anthers of some Angiosperms shows that there is a re- 
markable resemblance between the two cases. Similar irregularities 
have been noted, though less commonly, in Kaulfussia , and Marattia , 
and rarely in Angiopteris . 
Those fossil Marattiaceae which are best known as to the details of 
the sorus have been compared, and the substantial similarity of the 
sori in certain cases to those of the modern genera recognized. The 
facts from fossils and from the modern Marattiaceae have been made 
the basis for a fresh discussion of the theoretical question, whether 
the synangium is or is not a result of coalescence of sporangia? 
It is concluded that the palaeophytological evidence leaves the 
question open as to the priority of existence of forms with synangia, or 
with separate sporangia, in the Marattiaceae. Notwithstanding that 
writers of authority have treated the question as decided, that the 
synangia are a result of fusion of distinct sporangia, it is held with 
some persistence that it is still open ; the palaeophytological evidence 
is inconclusive, while the comparative evidence from the living 
genera will not only accord with, but appears actually to support 
a view of septation. 
For the analogy with septate anthers, where septation must have 
occurred, and the similarity between the details of these and those in 
Danaea , and especially the partial septations in both, make it appear 
probable that in this genus progressive septation has taken place. It 
is thought probable that progressive septation has been a feature, at 
least where the sori are elongated, as in Danaea . But the question 
is left over for future discussion whether or not a similar septation, 
rather than coalescence, may be accountable also for the origin in 
the first instance of a circular sorus with a plurality of sporangia 
united together as in Astero/heca, or in Pecopteris unita. 
