17 
A great many ferns range over more than one of these formations, 
both because they are not finely adapted to exact conditions — as, indeed, 
it is especially natural, in a mountainous country " that they shonld not 
be — and because, as already stated, the formations are not in mo5;t 
cases sliarply bounded. In the table each plant is ascribed to the for- 
iuation where the specimens represented in the table were collected; 
this was also the formation of which, on the M'liole, the plant seemed to 
me most characteristic. 
TUE STRAND. 
The characteristic strand fern of the Philippines is Niphoholus ad- 
nascens, which is found on the tree trunks over almost every beach in 
the Islands. Associated with it on the coconut boles and trunks at San 
!Rnmon are a small Bavallia solida and a remarkably dwarfed D. denti- 
culata. A diminutive form of Psilotiim nudum grows with tliem. A few 
miles from San Kamon, the mountains, bringing the high forest with 
them, conie close to the sea and here Polypodiuin stnuosam^ Asphniuni 
macrophyllumj A musaefolinm, and occasiounlly Drynaria qiiercifolia, 
are found on branches over the water where the reflected light and oc- 
casional spray must combine to make the habitat arid; these might all 
have been classified with the flora of the high forest, but the comparative 
want of ferns on tlie strand makes all but the last more conspicuous here. 
N eplirolepis hirsutula grows near enough to the beach at San Eamon to 
be a possible recipient of salt spray in hard winds. It is normally 
terrestrial but sometimes grows in a manner in which it has little if any 
connection with the ground. Next to Niphoholus, Nephrolepis is our 
most xerophytic genus, to judge by the difficulty encountered in drying 
the plants. With this occasional exception, every fern found on tlie San 
lijimon strand is epiphytic. The explanation of this habit is simple. 
The majority of the epiphytes in every formation — at any rate below the 
mossy forest — are vigorous xerophytes, in contrast on the whole, to the 
terrestrial ferns. On the strand, the epiphytic habitat is little if at all 
more arid than the terrestrial; it is more so with regard to the liglit, 
very little more so with regard to the wind, less so with regard to the 
salt. While the strand is altogether too arid to permit many terrestrial 
ferns even to become adapted, epiphytes can be at home on it with a 
r 
comparatively slight modification of their usual life and structure. 
Structures enabling a plant to endure intense insolation make strong 
illumination a necessity; no other plants receive as much light as strand 
epiphytes. On rocky shores of the Gulf of Davao a terrestrial fern, 
Chmlardhes Boltoni, grows just above high tide; its genus is character- 
istic of arid America. 
Of course, epiphytes are far from equally xerophytic, and only those 
which are the most so can endure strand conditions. These epiphytes 
•Copelaiid: Variation of some California plants. Bot. <Jaz. (1905), 38; 413. 
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