-j^g2 The Philippine Journal of Science 1913 
more juvenile being more likely to reveal di- or polymorphism, 
grown under conditions more or less favorable to luxuriant 
vegetation; and that the proper name to be given to all of 
these ferns is probably PhyllUis Durvillei (Bory) 0. Ktze. ^ 
We can now take up the interesting question of the origm 
and relationships of the genus Phyllitis, including all these forms. 
Christ has already declared that a number of them (see p. 148) 
are merely juvenile forms of Stenochlaena. On the same evi- 
dence, he has treated my Asplenium epiphyticum in the same 
way. I feel sure that in this he goes too far. I have studied 
the Asplenium carefully in the field, and have found it always 
to remain an Asplenium. Its polymorphism is a juvenile char- 
acter. With age, instead of proceeding to form pinnate fronds, 
as it should do if it were an immature Stenochlaena, it ceases 
to produce them, and finally bears only simple and fertile fronds. 
The evidence in the case of Phyllitis Durvillei is less complete, 
but all points in the same direction. The plants, as they mature, 
seem to grow away from polymorphism and partial sterility 
to complete fertility, with only simple fronds with the sori of 
Phyllitis, 
While the similarity of life-history of Asplenium epiphyticum, 
Phyllitis Durvillei, and Stenochlaena palustris is utterly in- 
adequate as evidence of their identity, it is the strongest kind 
of evidence they are closely related ferns. The three must 
have a rather recent common ancestry ; and the Asplenium must 
be regarded as the one which has most completely retained 
the characters of this common ancestor. For, as between Phyl- 
litis and Asplenium, the Asplenium has the simpler sorus, and 
represents a larger and more wide spread group ; and the an- 
cestor must be supposed to have been a fern with compound 
fronds, both on general grounds, such being the presumed com- 
mon ancestry of all Polypodiaceae, and on the particular ground 
that these ferns develop through such a stage. The Asplenium 
has such relatives in its genus, while the Phyllitis has not. 
Of the three ferns, the Stenochlaena has departed most widely 
from the ancestral form, as is shown by the high degree of 
specialization reached after the common part of the life-history 
has been grown through. 
Phyllitis Durvillei is accordingly to be regarded as descended 
from ferns of the genus Asplenium, its ancestor in that genus 
being A. epiphyticum or some very similar fern. And, this 
being so, it is also to be regarded as the most primitive species 
of Phyllitis. 
