io6 
Notes. 
examples may often be found where they vary to an extreme degree ; 
and these have an important bearing upon the theory of septation ; for 
cases of incomplete septation are often to be recognized in the mature 
sorus, while the study of earlier stages has revealed almost all imagin- 
able steps between the single loculus and two loculi lying side by side 
as an obvious pair. Such pairs of loculi are common ; sometimes the 
septum between them is of the average thickness; sometimes thin, 
but still complete, with firm, permanent tissue continuous across it ; 
sometimes the permanent tissue is incomplete, and the septum com- 
posed in its middle part only of tapetum, which disappears at 
maturity; sometimes a large loculus will be seen with only slight 
encroachments of tapetum upon the sporogenous group, thus indicating 
the position, though not realizing the complete development of a pos- 
sible septum ; the last step of the series would be simply a loculus 
larger than the average, and these are common. 
An analytical study of the tissues shows that the tissue of these 
partial septa may have either of two sources of origin : (i) single cells 
of the sporogenous group are liable to development as sterile cells ; 
this has been seen in sporangia which even approach the normal ; 
(2) the surrounding tissue may encroach on the sporogenous group, in 
the form of tapetal cells, which, when their development is considerable, 
is followed by cells of permanent tissue of the wall ; in these cases the 
partial septa will be clearly seen in the mature state. 
The similarity between these results and what is known in the case 
of septate anthers of Angiosperms is of peculiar interest ; in these 
anthers partial septa are common, and a detailed comparison of them 
with those of Danaea suggests that the phenomena are closely alike. 
But, in the case of the Angiospermic anthers, we conclude, on com- 
parative grounds, that progressive septation has taken place; this 
would indirectly support the view that the sorus of Danaea is also 
a result of progressive septation. 
Obviously such a series of stages as that presented by Danaea may 
be read either way, and it would be possible to urge that in them we 
have evidence, not of progressive septation, but of fusion of loculi. 
This question must be considered on grounds of general probability. 
Without at the moment declaring a final opinion (though I think the 
probability is largely in favour of a view of progressive septation), 
this point, at least, seems clear : that in Danaea the identity of the 
sporangium or locutus is not strictly defined. To arrive at this point is, 
