70 
wide distribution of tins spoeies and the great number of clearly derived 
forms, with simple and witli reticulate vein?. 
The suggestion that Hypolepis tenulfolia is really a Lastnea, or near 
it, is not new;^'' but even if this be its nature it may not throw any light 
on the origin of the real rtcrulecF., in which group this species is at 
best a rather foreign element. 
Nowhere else in the world do the Fohjpodieie reach a development com- 
parable either in number of species or in diversity, as is shown by the 
number of genera, to that attained in this Archipelago. They therefore 
present an especially advantageous field for local study. "Within tliis 
great tribe, it seems too clear for question that Eu poly podium is the 
parent, the center from which the other groups have been derived, but 
Eupolypodium itself, whatever its antiquity, is not in its characters a 
primitive group, being so specialized in adaptation to a habitat different 
from that of primitive ferns that it and its progeny have, the world 
over, become the predominant epiphytic ferns. Articulate stipes and 
comparative simplicity of frond are conspicuous adaptations to this 
habitat, and are characteristic of this tribe, but these same characters 
are, as has been seen, assumed by epiphytic plant^s of diverse origin, 
and the articulation is readily lost under conditions that render it 
superfluous. These facts make the tracing of the true origin of the 
tribe a difficult, perhaps an impossible, task. 
The articulation of the stipe may be of utility to a fern of cold 
countries, such as Polypodium vnlgare, permitting the ready casting of 
the leaves. Such a fern would readily adopt the epiphytic habit, under 
favorable conditions, and might have given rise to this tribe, but we 
bave no evidence of the development of articulate stipes by a terrestrial 
fern, and know that it has not occurred in most terrestrial ferns, even 
in cold regions. Therefore, it seems more reasonable to believe that 
P. vidgare has retained the articulations of epi2)hytic ancestors, being 
probably a plant the terrestrial habit of which, has permitted it to 
remain where it now lives, dating its origin from a time when the 
climate of the same region was favorable to epiphytic vegetation. Or, 
more prol^al^ly, Polypodium may have been derived from primitive ferns 
wbich evolved the present characters of the tribe in adaptation to 
epiphytic life. In this case, the ancestry was probably in Lastrcea, 
considering the instability of the indusium of this subgenus, and the 
known fact that it can develop articulations when an epiphyte. In the 
preceding section of this paper it was shown that in various minor 
groups within PoJypodivm there are species the stipes of which are 
inarticulate. It is not possible by any usable definition to exclude these 
species of Eupoly podium from Lastrcea and any one of them can readily 
be imagined to be a connecting link; but there is little reason to 
5 
M 
Polyprxliaeoiie of tlio Philippines. Oocf. Lah. Puhh (1905), 28: 95. 
