66 
Diacalpe in aspect and likewise suggestive in the same way of several 
species of Lastrcea, and, more remotely, of Monachosorum. I have a 
single specimen, the majority of the indusia of which are reniform and 
fixed by the sinus, as in N ephr odium, but which has certain of them 
fixed by the base, more or less broad, and a few, unequal-sided, exactly 
like those of Athyrium. I should not know where else to look for the 
origin of Diacalpe , if not in Acrophorus. 
On the internal evidence of the Davallietc, Microlepia is certainly 
to be regarded as the central genus, to which most other genera are 
evidently related; and I am strongly inclined to believe that it is also 
the most primitive, although a possible relation between Leucostegia 
and Acrophorus has just been mentioned. In habitat and aspect, .and 
in all essential characters except the indusium, Microlepia agrees wdth 
some of the most primitive Aspidiece ( Lastrace ). M. strigosa and il f. 
rhomboidea are strikingly Polystichum-like in aspect, but I do not 
regard this as due to affinity. Of the other genera of the Davalliece, 
Wibelia is sometimes included in Microlepia , and is -certainly near it. 
Of all our ferns it is the most constantly unstable in form. A fern of 
my Mount Apo collection stands so exactly on the line between Microlepia 
and Dennstaedtia that it might be included in one practically as easily 
as in the other. Because the sori are not always quite marginal, and 
by the structure of the receptacle, which I do not regard as really diag- 
nostic, I described it as Microlepia, M. dennstaedtioides ; but Christ was 
rather disposed to call it Dennstaedtia. Dennstaedtia is still too clearly 
a natural group to lose its generic identity because it is intimately related 
to its parent. 
In Microlepia, as in Lastrcea, there is at San Ramon a solitary epiphytic 
species, M. hirsuta , 33 the stipe of which is appropriately articulate. While 
it is hardly probable that this species is an ancestor of our epiphytic 
Davalliaece, it shows how easily they may have originated in Microlepia, 
Davallia is the nearest epiphytic genus, and there is also in Mindanao a 
Davallia, D. ivagneriana, the lowest pinna? of whi ch are not enlarged, 
but it differs from M. hirsuia in several important respects. 
Unless, which is hardly probable, Lenicostegia had an independent 
origin wuthout the Davalliece, it may best be regarded as a near derivative 
of Microlepia, though Davallia pallida approaches Leucostegia in the 
large free part of the indusium. ILumata is probably derived from 
Leucostegia, the strong resemblance to Davallia being in adaptation to 
their common environment. However, there are other points of possible 
contact between all these genera, and real affinities are still somewhat 
a matter of guesswork. Even the natural generic limits are not certain. 
33 This argument loses none of its force if the species be removed from Micro- 
lepia, as a separate genus; its affinity to Microlepia is unmistakable, whatever 
name it bears. 
