the more primitive type in the Ferns ? 1 3 1 
of the latter. It is probable that in the course of evolution 
of the Filicineae, the originally united archesporium became 
partitioned by bands of sterile tissue, each portion, thus 
isolated, developing together with its superficial covering of 
cells into a sporangium : if this were so, it follows that 
we may recognise in the synangia or so-called * coalescent 
sporangia ’ of the Marattiaceae, and also in the ‘ sporangio- 
phore ’ of Ophioglossum , instances of the incomplete separation 
of the individual sporangia, though the archespore in each 
is separate from that of its neighbours 1 . From a com- 
parative point of view I am disposed to regard these 
synangia, which are found in more than one series of the 
Vascular Cryptogams, as primitive in character, and as 
indicating not a coalescence of sporangia which were distinct 
in more ancestral forms, but rather an incomplete separation 
of sporangia, whose distinct archesporial cells were derived 
by isolation from some such united ancestral archesporium 
as is seen in the Bryophyta of the present day. If such 
Eusporangiate forms with synangial sori were the more 
primitive, it is not difficult to conceive how in plants 
growing in moist and shaded positions, where the danger of 
exposure to drought is minimised, the sporangia might 
have become not only completely separate, but also reduced 
in bulk, as we see in the progression through the Os- 
mu ndaceae to the truly Leptosporangiate Ferns : and parallel 
with this reduction of the sporangium, as I have shown else- 
where, would have proceeded the reduction in mass of all the 
other members of the sporophyte. 
Again, this view that the Eusporangiate Ferns were the 
more primitive, and the Leptosporangiate derivative and 
specialised, may throw light upon what I have hitherto re- 
garded as a perplexing phenomenon, I mean apospory: it 
was difficult to understand why this obliteration of a marked 
phase in the alternation should make its appearance in 
forms which we were accustomed to accept as primitive, 
seeing that on other grounds it is regarded as a terato- 
1 Compare D. Campbell, 1. c. 
