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 6 that they should not 
be — and because, as already stated, the formations are not in most 
cases sharply bounded. In the table each plant is ascribed to the for- 
mation where the specimens represented in the table were collected; 
this was also the formation of which, on the whole, the plant seemed to 
me most characteristic. 
THE STRAND. 
The characteristic strand fern of the Philippines is Niphobolus 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 
Eamon are a small Davallia solida and a remarkably dwarfed D. denti- 
culate/,. A diminutive form of Psilotum nudum grows with them. A few 
miles from San Eamon, the mountains, bringing the high forest with 
them, come close to the sea and here Polypodium sinuosum, Asplenium 
macrophyllum, A musaefolium, and occasionally Drynaria quercifolia, 
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 the strand makes all but the last more conspicuous here. 
Nephrolepis 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 Niphobolus, Nephrolepis is our 
most xerophytic genus, to judge by the difficulty encountered in drying 
the plants. With this occasional exception, every fern found on the San 
Eamon 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 light, 
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 
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, 
Gheilanthes 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 
6 Copeland: Variation of some California plants. Bot. Gas. (1905),. 38; 413. 
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