ix, c. 3 Robinson: Distribution of Philippine Mosses 215 
From a general consideration of the species of the genera 
concerned, as well as of the Philippine localities cited, it would 
appear that Trichostomum subduriusculum and Entodon longi- 
dens offer no conclusive evidence in either direction, while the 
three species of E ctropothecium, Symphysodontella subulata, Ve- 
sicularia campylothecium, and Meiothecium attenuatum have 
more likely originated farther south and thence migrated to the 
Mountain Province. 
Similar arguments render it probable that the remaining five 
originated in the Mountain Province, and have spread thence 
to a greater or less extent, along two lines of distribution. Two 
are known both from Banajao and the mountains of Zambales, 
and it is much less probable that they passed directly from 
either of these to the other than that they have reached both 
from Benguet. Moreover, one other is known only in the Moun- 
tain Province and on Banajao; neither of the others is known 
from Banajao, but both occur in Zambales, one of the latter 
extending through what is the same and a continuation of the 
same range to Abu and Mariveles, and to a far-off station in 
Mindanao. 
It is admitted that very little has been proven on this head, 
but it is to be remembered that nothing would be more de- 
structive of one of the main points here sought to be established, 
than the discovery that any very high proportion of the species 
which seem to have originated in the Mountain Province had 
migrated to the south. 
When the essential of the east-west coast theory of distribu- 
tion is understood, its inherent probability will be universally 
conceded. For it is no more than this. Can the plants of the 
Philippines be divided into two physiological groups, those which 
can withstand a long-continued period of drought, and those 
which can not? Briefly, the answer is in the affirmative, but 
complications are at once introduced by plants which prefer the 
one set of conditions but tolerate the other, and by the ascer- 
tained fact that the humidity of any part of the Philippines 
is high even in its dry season. The facts are capable of another 
explanation. Both groups of plants may prefer the one set of 
conditions, presumably in at least most cases the more even 
distribution of rain. Under such conditions, the one group may 
be superior to the other in the struggle for existence. When 
confronted with less desirable conditions, that group may no 
longer be able to compete on favorable terms, and thus will yield 
supremacy to their rivals. From a purely floristic point of 
view, it is of little consequence which of these furnishes the better 
