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change appears to be remarkably abrupt, because the lower trees render 
the plants more visible to the casual observer, but in reality it is not so 
great as at first it would seem to be. It has already been noted that to- 
ward the upper limits of and in more favorable situations in the Shorea- 
Plectronia formation, there is a tolerably rich display of epiphytes, which 
in the more closed places of the forest are confined to the large limbs of 
the tallest trees, because the shade of the latter is so dense as to exclude 
plants accustomed to places having more light. However, as the higher 
and more exposed altitudes are reached and trees become lower, epiphytic 
vegetation, represented by mosses, a few liverworts, and an occasional 
orchid or fern, is found not only on the limbs but also on the trunks 
of the trees, so that, advancing from Plots A to H there is a gradual 
increase in richness of the epiphytes. This increase is in direct cor- 
respondence with the rise in the humidity. As has already been men- 
tioned, the region near the top of the mountain is more often enveloped 
in a dense fog than are’ the other parts and to this difference in 
humidity the wealth of epiphytes can be ascribed. It is a well-known 
fact that plants, especially orehids, which depend on the moisture of the 
atmosphere for the water which they absorb, are not capable of con- 
densing the vapor present therein but on the contrary, must have 
condensed water for their needs—that is, the moisture must be accessible 
to them in the form of rain or mist. In plants with absorbing organs 
adapted to take up moisture from the air, and exposed alternatingly 
to a very moist and a very dry atmosphere, xerophytic adaptations are 
“necessary. 
For the purposes of this paper, the epiphytic vegetation of Mount Mari- 
veles may be divided into three groups, viz, (1) plants with xerophytic, 
photosynthetic organs and special adaptation for absorbing moisture ; 
(2) those with mesophytic leaves which, by assuming the so-called resur- 
rection form, can withstand loss of moisture and (3) the forms with 
xerophytic leaves and with no special adaptations for absorbing moisture. 
The lichens and orchids belong to the first group, and these are classed 
together because the velamen of the orchid roots, in times of drought 
and excessive moisture, behaves in the same manner as does the fungus 
element of lichens. On the trunks of the trees situated at the mountain 
top but few lichens are found, because these more favorable situations 
are quickly occupied by other less humble epiphytes; as a result the lichens 
are confined to the faces of newly broken rocks whereas the older ones are 
as densely covered with mosses, liverworts, and ferns as are the trunks 
of the trees.49 The trees of the lower altitudes, with trunks the bark 
of which is smooth and not frequeritly shed, are often so thickly covered 
with crustaceous species of lichens as to render it almost out of the 
” Strictly speaking, of course plants growing on rocks are lithophytes. Ecolog- 
ically they are like epiphytes and are here classified as such. 
